Patent Application
20220056457
The present invention relates in general to plasmid systems, more particularly to cis conjugative plasmid systems and methods of using cis conjugative plasmid systems for altering a microbiome or biofilm or detecting constituents of a microbiome or biofilm.
Microbial ecosystems are essential for human health and proper development, and disturbances of the ecosystem correlate with a multitude of diseases [1-5]. A central problem is the lack of tools to selectively control pathogenic species that cause disease, or to otherwise alter or transform the composition of the human or non-human microbiome.
Microbes persisting in a biofilm in the human body cause about two-thirds of all chronic/recurrent diseases. These biofilms are composed of bacteria and other microbes protected by an extracellular matrix that is often made up of polysaccharides, proteins and DNA which prevents the innate and adaptive immune systems, antibiotics, bacteriophage and other antibacterial agents from gaining access to the bacteria inside the biofilm. Biofilms protect the microbes by forming a barrier and make it extremely difficult to clear the infection from the body. Furthermore, biofilms can act as a reservoir for future acute infections often with lethal consequences.
Traditional methods to modify microbial communities suffer from a number of disadvantages or limitations.
Antibiotic treatment suffer from a number of limitations that preclude selective control in a defined and efficient manner, and are becoming less effective because of overuse and the development of multi-drug resistant bacteria.
Phage-based therapy is limited by host range and the rapid development of phage-resistant bacteria [6].
Probiotics and prebiotics are effective but of use in only a few defined conditions [7].
Stool transplants are effective treatments for gastrointestinal dysbioses, but can result in wide-spread alterations in the composition of the microbial ecosystem with unknown long-term effects [8-10].
The limitations of the traditional methods highlight an increasing need for effective and selective tools for the targeted modification of microbiomes.
Conjugative plasmids are an attractive tool to alter or modify microbiomes because conjugative plasmids have broad host ranges, are generally tought to be resistant to restriction-modification systems, are easy to engineer with large coding capacities, and do not require a cellular receptor that would provide a facile mechanism for bacterial resistance.
A low efficiency of conjugation was found to be a limiting factor in the use of trans-conjugative plasmids.
In view of the foregoing, a new tool to modify microbiomes efficiently and without including the limitations of the prior art is needed.
Provided herein is a new cis-conjugative plasmid system and method of using said cis conjugative plasmid system in altering a bacterial microbiome or biofilm. The cis-conjugative plasmid encodes both the conjugative machinery and a gene or combination of genes of interest to alter or modify or modulate target bacteria species in the bacterial microbiome or biofilm, as opposed to previously tested trans setups where the conjugation machinery and gene of interest were separated (
In one embodiment, the present invention is a method for modulating a target organism in a microbiome, comprising contacting the microbiome with a cis-conjugative plasmid that can replicate and conjugate with organisms in the microbiome including the target organism, the cis-conjugative plasmid comprising (i) conjugation genes (i.e. the conjugation machinery) and (ii) a gene or a combination of genes capable of being expressed in the target organism and that modulates the target organism in the microbiome (i.e. gene that modulates the target organism or modulating gene).
In another embodiment, the present invention is a method for modulating a target organism in a microbial biofilm, comprising contacting the microbial biofilm with a cis-conjugative plasmid that can replicate in and conjugate to organisms in the microbial biofilm including the target organism, the cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a gene or a combination of genes capable of being expressed in the target organism and that modulates the target organism in the microbial biofilm (i.e. gene that modulates the target organism or modulating gene).
In another embodiment, the present invention is a method for inhibiting, preventing or treating an infection caused by an organism (“target organism”) that can accept by conjugation and express a conjugative plasmid in a subject, comprising administering to the subject an effective amount of a cis-conjugative comprising conjugation genes (i.e. the conjugation machinery) and a gene or a combination of genes capable of being expressed in the target organism and that modulates the target organism in the microbiome (i.e. gene that modulates the target organism or modulating gene to inhibit, prevent or treat the infection), thereby inhibiting, preventing or treating the infection.
In another embodiment, the present invention is a method for propagating a gene of interest in a target organism within a microbiome or biofilm, comprising contacting the microbiome or biofilm with a cis-conjugative plasmid that can replicate and conjugate organisms in the microbiome or biofilm including the target organism, the cis-conjugative plasmid comprising conjugation genes and a gene or a combination of genes capable of being expressed in the target organism and that modulates the target organism in the microbiome or biofilm to propagate the gene of interest.
In one embodiment of any of the methods of the present invention, the cis-conjugative plasmid further comprises a single or multiple single-guide RNAs corresponding to a single or multiple target sites of the target organism.
In one embodiment of any of the methods of the present invention, the gene that modulates the target organism is a coding region for TevCas9 nuclease gene.
In another embodiment according to any of the methods of the present invention, the gene that modulates the target organism is a coding region for a site-specific DNA endonuclease
In another embodiment according to any of the methods of the present invention, the gene that modulates the target organism is a coding region for a bacterial toxin, wherein the bacterial toxin includes DNA gyrase inhibitors or topoisomerase inhibitors.
In another embodiment according to any of the methods of the present invention, the gene that modulates the target organism is a coding region for a gene or genes for biosynthetic or biodegradative pathways.
In another embodiment according to any of the methods of the present invention, the gene that modulates the target organism is a coding region for regulatory sequence including small RNA molecules or transcription factors.
In another embodiment according to any of the methods of the present invention, the contacting is in vitro or in vivo.
In another embodiment according to any of the methods of the present invention, the target organism is a bacterium.
In another embodiment, the present invention provides an isolated or recombinant cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a gene or a combination of genes capable of being expressed in a target bacteria within a microbiome or biofilm and that modulates the target bacteria in the microbiome or biofilm (i.e. the gene that modulates the target bacteria or modulating gene).
In one embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention, the isolated cis-conjugative plasmid further comprises a single or multiple single-guide RNAs corresponding to a single or multiple target sites of the target bacteria.
In one embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention the gene that modulates the bacteria is a coding region for TevCas9 nuclease gene and guide RNA.
In another embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention the gene that modulates the target bacteria is a coding region for a site-specific DNA endonuclease
In another embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention the gene that modulates the target bacteria is a coding region for a bacterial toxin, wherein the bacterial toxin includes DNA gyrase inhibitors or topoisomerase inhibitors.
In another embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention the gene that modulates the target bacteria is a coding region for a gene or genes for biosynthetic or biodegradative pathways.
In another embodiment of the isolated or recombinant cis-conjugative plasmid of the present invention the gene that modulates the target bacteria is a coding region for regulatory sequence including small RNA molecules or transcription factors.
In another embodiment, the present invention relates to a use of a cis-conjugative plasmid for modulating a target organism in a microbiome or microbial biofilm, the cis-conjugative plasmid being engineered to replicate and conjugate with organisms in the microbiome or microbial biofilm including the target organism, the cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a gene or a combination of genes capable of being expressed in a target bacteria within the microbiome or microbial biofilm and that modulates the target organism in the microbiome or microbial biofilm (i.e. the gene that modulates the target bacteria or modulating gene).
In another embodiment, the present invention relates to a use of a cis-conjugative plasmid for inhibiting, preventing or treating an infection caused by an organism that can accept by conjugation and express a conjugative plasmid in a subject, the cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a gene or a combination of genes capable of being expressed in a target bacteria within the microbiome or microbial biofilm and that modulates the organism that causes the infection to inhibit, prevent or treat the infection, thereby inhibiting, preventing or treating the infection.
In another embodiment, the present invention relates to a use of a cis-conjugative plasmid for propagating a gene of interest in a target organism within a microbiome or biofilm, the cis-conjugative plasmid being capable to replicate and conjugate organisms in the microbiome or biofilm including the target organism, the cis-conjugative plasmid comprising conjugation genes and a gene or a combination of genes capable of being expressed in the target organism and that modulates the target organism in the microbiome or biofilm to propagate the gene of interest.
In one embodiment of the use according to any one of the previous embodiments, the cis-conjugative plasmid further comprises a single or multiple single-guide RNAs corresponding to a single or multiple target sites of the target organism.
In one embodiment of the use according to any of the previous embodiments, the gene that modulates the target organism is a coding region for TevCas9 nuclease gene.
In one embodiment of the use according to any of the previous embodiments, the gene that modulates the target organism is a coding region for a site-specific DNA endonuclease
In one embodiment of the use according to any of the previous embodiments, the gene that modulates the target organism is a coding region for a bacterial toxin, wherein the bacterial toxin includes DNA gyrase inhibitors or topoisomerase inhibitors.
In one embodiment of the use according to any of the previous embodiments, the gene that modulates the target organism is a coding region for a gene or genes for biosynthetic or biodegradative pathways.
In one embodiment of the use according to any of the previous embodiments, the gene that modulates the target organism is a coding region for regulatory sequence including small RNA molecules or transcription factors.
In one embodiment of the use according to any of the previous embodiments, the contacting is in vitro or in vivo.
In one embodiment of the use according to any of the previous embodiments, the target organism is a bacterium.
In another embodiment, the present invention relates to a method of diagnosing an infection caused by a bacteria, the method comprising contacting a site of the infection with a cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a detectable gene specific for the bacteria that causes the infection.
In one embodiment of the method of diagnosing, the detectable gene expresses a detectable protein when the detectable gene is activated by an activator when the activator is in operative proximity to the detectable gene.
In another embodiment of the method of diagnosing, the activator is a transcriptional activation domain.
In another embodiment of the method of diagnosing, the detectable gene is a transposon for transposon-based tagging.
In another embodiment, the present invention is a method of detecting the presence of a bacteria of interest in a microbiome, the method comprising contacting the microbiome with a cis-conjugative plasmid comprising conjugation genes (i.e. the conjugation machinery) and a detectable gene that can only be expressed and active in the bacteria of interest.
In another embodiment, the present invention relates to a kit comprising: (a) an isolated cis-conjugative plasmid comprising conjugation genes and a gene or a combination of genes capable of being expressed in a target organism within a microbiome or biofilm that modulates the target organism in the microbiome or biofilm according to an embodiment of the present invention; and (b) instructions for use in inhibiting, preventing or treating an infection caused by the target organism in the microbiome or biofilm.
In another embodiment, the present invention is an isolated or recombinant nucleic acid sequence comprising SEQ ID NO:66 or an isolated or recombinant nucleic acid sequence having at least 80% sequence identity to SEQ ID NO:66.
In another embodiment, the present invention is an isolated functional fragment of SEQ ID NO:66,
The following figures illustrate various aspects and preferred and alternative embodiments of the invention.
The practice of the present invention will employ, unless otherwise indicated, conventional techniques of tissue culture, immunology, molecular biology, microbiology, cell biology and recombinant DNA, which are within the skill of the art. See, e.g., Sambrook and Russell eds. (2001) Molecular Cloning: A Laboratory Manual, 3rd edition; the series Ausubel et al. eds. (2007) Current Protocols in Molecular Biology; the series Methods in Enzymology (Academic Press, Inc., N.Y.); MacPherson et al. (1991) PCR 1: A Practical Approach (IRL Press at Oxford University Press); MacPherson et al. (1995) PCR 2: A Practical Approach; Harlow and Lane eds. (1999) Antibodies, A Laboratory Manual; Freshney (2005) Culture of Animal Cells: A Manual of Basic Technique, 5th edition; Gait ed. (1984) Oligonucleotide Synthesis; U.S. Pat. No. 4,683,195; Hames and Higgins eds. (1984) Nucleic Acid Hybridization; Anderson (1999) Nucleic Acid Hybridization; Hames and Higgins eds. (1984) Transcription and Translation; Immobilized Cells and Enzymes (IRL Press (1986)); Perbal (1984) A Practical Guide to Molecular Cloning; Miller and Calos eds. (1987) Gene Transfer Vectors for Mammalian Cells (Cold Spring Harbor Laboratory); Makrides ed. (2003) Gene Transfer and Expression in Mammalian Cells; Mayer and Walker eds. (1987) Immunochemical Methods in Cell and Molecular Biology (Academic Press, London); and Herzenberg et al. eds (1996) Weir's Handbook of Experimental Immunology.
All numerical designations, e.g., pH, temperature, time, concentration and molecular weight, including ranges, are approximations which are varied (+) or (−) by increments of 1.0 or 0.1, as appropriate, or alternatively by a variation of +/−15%, or alternatively 10%, or alternatively 5% or alternatively 2%. It is to be understood, although not always explicitly stated, that all numerical designations are preceded by the term “about”. It also is to be understood, although not always explicitly stated, that the reagents described herein are merely exemplary and that equivalents of such are known in the art.
As used in the specification and claims, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a polypeptide” includes a plurality of polypeptides, including mixtures thereof.
As used herein, the term “comprising” is intended to mean that the compositions and methods include the recited elements, but do not exclude others. “Consisting essentially of” when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination for the intended use. Thus, a composition consisting essentially of the elements as defined herein would not exclude trace contaminants from the isolation and purification method and pharmaceutically acceptable carriers, such as phosphate buffered saline, preservatives and the like. “Consisting of” shall mean excluding more than trace elements of other ingredients and substantial method steps for administering the compositions of this invention. Embodiments defined by each of these transition terms are within the scope of this invention.
As used herein “contacting” means any method to deliver the conjugative plasmid to a microbial cell or to a biofilm using standard microbiological or molecular biological techniques including, but not limited to plasmid transformation, conjugation, electroporation, transfection, transduction. The plasmid can be delivered as an isolated DNA or isolated plasmid, or it can be delivered within a system by being carried in another bacterium, bacteriophage, a liposome or any other cell delivery system. The plasmid may also be delivered naked.
A “biofilm” intends to mean a thin layer or an organized community of microorganisms that at times can adhere to the surface of a structure that may be organic or inorganic, together with the polymers, such as polysaccharides, proteins and DNA, that they secrete and/or release. Biofilms are very resistant to microbiotics and antimicrobial agents. They live on gingival tissues, teeth and restorations, causing caries and periodontal disease, also known as periodontal plaque disease. Biofilms are the natural state of the majority of bacteria in contact with any epithelial cell surface. They also cause chronic middle ear infections. Biofilms can also form on the surface of dental implants, stents, catheter lines and contact lenses. They grow on pacemakers, heart valve replacements, artificial joints and other surgical implants. The Centers for Disease Control estimate that over 65% of nosocomial (hospital-acquired) infections are caused by biofilms. Fungal biofilms also frequently contaminate medical devices. They cause chronic vaginal infections and lead to life-threatening systemic infections in people with hobbled immune systems. They occur in life-threatening diseases of the colon such as Clostridium dificile infection. Biofilms also are involved in numerous diseases. For instance, cystic fibrosis patients have Pseudomonas infections that often result in antibiotic resistant biofilms.
A “microbiome” is used in this document as a community of microorganisms (such as bacteria, fungi, archea, viruses and small eukaryotes) that inhabit an organic (including biological) or inorganic surface. In the context of this invention, a microbiome includes any of the above that can accept by conjugation and express the cis-conjugative plasmid of the present invention. Biological surfaces include the human or non-human bodies. Non-biological surfaces may include solid surfaces such as table tops, curtains, filters, industrial tools, industrial bioreactors, environmental surfaces and so forth. The GI tract microbiota has been implicated in disease states such as inflammatory bowel disease, colon cancer, gastric cancer, and irritable bowel syndrome. In addition, a relationship exists between diet, microbiota, and health status, particularly in older subjects.
A “subject” of treatment is a cell or an animal such as a mammal or a human. Non-human animals subject to treatment and are those subject to infections or animal models, for example, simians, murines, such as, rats, mice, chinchilla, canine, such as dogs, leporids, such as rabbits, livestock, sport animals and pets. Non-animal subjects of treatment would include as non-exclusive examples bioreactors, treatment plants, landfills etc.
The term “isolated” or “recombinant” as used herein with respect to nucleic acids, such as DNA or RNA, or plasmids refers to molecules separated from other DNAs or RNAs, respectively that are present in the natural source of the macromolecule as well as polypeptides. The term “isolated or recombinant plasmids” is meant to include plasmids which are not naturally occurring as fragments and would not be found in the natural state. The term “isolated” is also used herein to refer to polynucleotides, polypeptides and proteins that are isolated from other cellular proteins and is meant to encompass both purified and recombinant polypeptides. In other embodiments, the term “isolated or recombinant” means separated from constituents, cellular and otherwise, in which the cell, tissue, polynucleotide, peptide, polypeptide, protein, antibody or fragment(s) thereof, which are normally associated in nature. For example, an isolated cell is a cell that is separated from tissue or cells of dissimilar phenotype or genotype. An isolated polynucleotide is separated from the 3′ and 5′ contiguous nucleotides with which it is normally associated in its native or natural environment, e.g., on the chromosome. As is apparent to those of skill in the art, a non-naturally occurring polynucleotide, peptide, polypeptide, protein, antibody or fragment(s) thereof, does not require “isolation” to distinguish it from its naturally occurring counterpart.
As used herein, the terms “treating,” “treatment” and the like are used herein to mean obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disorder or sign or symptom thereof and/or may be therapeutic in terms of a partial or complete cure for a disorder and/or adverse effect attributable to the disorder.
To “prevent” intends to prevent a disorder or effect in vitro or in vivo in a system or subject that is predisposed to the disorder or effect. An example of such is preventing the formation of a biofilm in a system that is infected with a microorganism known to produce one.
“Pharmaceutically acceptable carriers” refers to any diluents, excipients or carriers that may be used in the compositions of the invention. Pharmaceutically acceptable carriers include ion exchangers, alumina, aluminum stearate, lecithin, serum proteins, such as human serum albumin, buffer substances, such as phosphates, glycine, sorbic acid, potassium sorbate, partial glyceride mixtures of saturated vegetable fatty acids, water, salts or electrolytes, such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, zinc salts, colloidal silica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-based substances, polyethylene glycol, sodium carboxymethylcellulose, polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers, polyethylene glycol and wool fat. Suitable pharmaceutical carriers are described in Remington's Pharmaceutical Sciences, Mack Publishing Company, a standard reference text in this field. They are preferably selected with respect to the intended form of administration, that is, oral tablets, capsules, elixirs, syrups and the like and consistent with conventional pharmaceutical practices.
“Administration” can be effected in one dose, continuously or intermittently throughout the course of treatment. Methods of determining the most effective means and dosage of administration are known to those of skill in the art and will vary with the composition used for therapy, the purpose of the therapy, the target cell being treated and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician. Suitable dosage formulations and methods of administering the agents are known in the art. Route of administration can also be determined and method of determining the most effective route of administration are known to those of skill in the art and will vary with the composition used for treatment, the purpose of the treatment, the health condition or disease stage of the subject being treated and target cell or tissue. Non-limiting examples of route of administration include oral administration, nasal administration, injection and topical application.
“Plasmid” refers to an extra-chromosomal DNA molecule separate from the chromosomal DNA. Plasmids replicate extra-chromosomally inside a cell and can transfer their DNA from one cell to another by a variety of mechanisms. DNA sequences controlling extra chromosomal replication (ori) and transfer (tra) are distinct from one another; i.e., a replication sequence generally does not control plasmid transfer, or vice-versa.
A “conjugative plasmid” is a plasmid that is transferred from one organism, such as a bacterial cell, to another organism during a process termed conjugation. The term refers to a self-transmissible plasmid that carries genes promoting the plasmid's own transfer by conjugation. Cis-conjugative plasmids carry their own origin of replication, oriV, and an origin of transfer, oriT, and genes promoting the plasmid's own transfer by the conjugation process. When conjugation is initiated, a relaxase enzyme creates a “nick” in one plasmid DNA strand at the oriT. The enzyme may work alone or in a complex of over a dozen proteins. The transferred, or T-strand, is unwound from the plasmid and transferred into the recipient bacterium in a 5′-terminus to 3′-terminus direction through a conjugative pilus. The remaining strand is replicated, either independent of conjugative action (vegetative replication, beginning at the oriV) or in concert with conjugative replication. Conjugation functions can be plasmid encoded, but some conjugation genes can be found in the bacterial chromosome or another plasmid and can exhibit their activity in trans to a separate plasmid that encodes the oriT sequence. Numerous conjugative plasmids are known, which can transfer associated genes within one species (narrow host range) or between many species (broad host range). Conjugation can occur between species classified as different at any taxonomic level—including in the extreme between domains, e.g. bacteria to eukaryotes.
A cis-conjugative plasmid is a plasmid that encodes both the conjugative machinery and a gene or combination of genes for targeted bacterial modulation, including killing of bacteria (such as CRISPR nuclease), metabolic manipulation of bacteria and augmentation of beneficial bacteria, as well as for the detection of bacteria and so forth.
The term “effective amount” refers to a quantity sufficient to achieve a beneficial or desired result or effect. In the context of therapeutic or prophylactic applications, the effective amount will depend on the type and severity of the condition at issue and the characteristics of the individual subject, such as general health, age, sex, body weight, and tolerance to pharmaceutical compositions. In the context of an immunogenic composition, in some embodiments the effective amount is the amount sufficient to result in a protective response against a pathogen. In other embodiments, the effective amount of an immunogenic composition is the amount sufficient to result in antibody generation against the antigen. In some embodiments, the effective amount is the amount required to confer passive immunity on a subject in need thereof. With respect to immunogenic compositions, in some embodiments the effective amount will depend on the intended use, the degree of immunogenicity of a particular antigenic compound, and the health/responsiveness of the subject's immune system, in addition to the factors described above. The skilled artisan will be able to determine appropriate amounts depending on these and other factors.
In the case of an in vitro application, in some embodiments the effective amount will depend on the size and nature of the application in question. It will also depend on the nature and sensitivity of the in vitro target and the methods in use. The skilled artisan will be able to determine the effective amount based on these and other considerations. The effective amount may comprise one or more administrations of a composition depending on the embodiment.
The agents and compositions can be used in the manufacture of medicaments and for the treatment of humans and other animals by administration in accordance with conventional procedures, such as an active ingredient in pharmaceutical compositions.
An agent of the present invention can be administered for therapy by any suitable route of administration. It will also be appreciated that the preferred route will vary with the condition and age of the recipient and the disease being treated.
The terms “equivalent” or “biological equivalent” are used interchangeably when referring to a particular molecule, biological, or cellular material and intend those having minimal homology while still maintaining desired structure or functionality.
It is to be inferred without explicit recitation and unless otherwise intended, that when the present invention relates to a plasmid, polypeptide, protein, or polynucleotide, an equivalent or a biologically equivalent of such is intended within the scope of this invention. As used herein, the term “biological equivalent thereof” is intended to be synonymous with “equivalent thereof” when referring to a reference protein, antibody, polypeptide or nucleic acid or plasmid, intends those having minimal homology while still maintaining desired structure or functionality. Unless specifically recited herein, it is contemplated that any polynucleotide, polypeptide or protein mentioned herein also includes equivalents thereof. For example, an equivalent intends at least about 70% homology or identity, or alternatively about 80% homology or identity and alternatively, at least about 85%, or alternatively at least about 90%, or alternatively at least about 95% or alternatively 98% percent homology or identity and exhibits substantially equivalent biological activity to the reference protein, polypeptide or nucleic acid. In another aspect, the term intends a polynucleotide that hybridizes under conditions of high stringency to the reference polynucleotide or its complement.
A polynucleotide or polynucleotide sequence (or a polypeptide or polypeptide sequence) having a certain percentage (for example, 80%, 85%, 90% or 95%) of “sequence identity” to another sequence means that, when aligned, that percentage of bases (or amino acids) are the same in comparing the two sequences. The alignment and the percent homology or sequence identity can be determined using software programs known in the art, for example those described in Current Protocols in Molecular Biology (Ausubel et al., eds. 1987) Supplement 30, section 7.7.18, Table 7.7.1. Preferably, default parameters are used for alignment. A preferred alignment program is BLAST, using default parameters. In particular, preferred programs are BLASTN and BLASTP, using the following default parameters: Genetic code=standard; filter=none; strand=both; cutoff=60; expect=10; Matrix=BLOSUM62; Descriptions=50 sequences; sort by=HIGH SCORE; Databases=non-redundant, GenBank+EMBL+DDBJ+PDB+GenBank CDS translations+SwissProtein+SPupdate+PIR. Details of these programs can be found at the following Internet address: ncbi.nlm.nih.gov/cgi-bin/BLAST.
“Homology” or “identity” or “similarity” refers to sequence similarity between two peptides or between two nucleic acid molecules. Homology can be determined by comparing a position in each sequence which may be aligned for purposes of comparison. When a position in the compared sequence is occupied by the same base or amino acid, then the molecules are homologous at that position. A degree of homology between sequences is a function of the number of matching or homologous positions shared by the sequences. An “unrelated” or “non-homologous” sequence shares less than 30% identity or alternatively less than 25% identity, less than 20 identity, or alternatively less than 10% identity with one of the sequences of the present invention.
“Homology” or “identity” or “similarity” can also refer to two nucleic acid molecules that hybridize under stringent conditions to the reference polynucleotide or its complement.
Overview
Provided herein is a new cis-conjugative plasmid system and method of using said cis-conjugative plasmid system in altering or modulating or modifying a bacterial microbiome, including biofilms. In one embodiment, the cis-conjugative plasmid of the present invention encodes both the conjugative machinery and a gene or genes of interest that is/are capable of being expressed in a target bacteria species of interest within a microbiome or biofilm, and that serves to alter or modulate only the target bacteria species in the microbiome or biofilm, as opposed to previously tested trans setups where the conjugation machinery and gene of interest were separated (
Applications
The gene or genes of interest may be a gene or genes that alters, modifies, modulates or manipulates the bacteria, or a subpopulation of bacteria in the bacterial microbiome or biofilm. The cis-conjugative plasmid of the present invention may include a gene or combination of genes to target specific bacteria within a population of different bacterial species. While any bacterium in the bacterial microbiome/biofilm that receives the cis-conjugative plasmid of the present invention becomes a donor for subsequent rounds of re-conjugation, leading to exponentially increasing numbers of conjugative donor bacteria in a population of bacteria such as a microbiome or a biofilm carrying the gene of interest, only the target specific bacteria within the population is modulated. The applicant surprisingly discovered a high degree of efficiency in the conjugative transfer of the cis-conjugative plasmid of the present invention intra-species and inter-species of bacteria. As such, the systems and methods of the present invention can be used as effective tools in the manipulation of microbiomes. The present invention also relates to cis-conjugated plasmids engineered so that the gene product is only active in a target bacteria.
The gene or combination of genes of interest may include genes that lead to the killing of the target bacteria, or to the growth of beneficial bacteria, or to the production of molecules of interest and so forth. The gene or combination of genes may include inducible genes that are turned on and off when certain conditions are met. For example, pH and temperature may change along the Gastrointestinal (GI) tract. pH or Temperature-sensitive genes having permissive and non-permissive pHs/temperatures could be used to deliver the plasmids of the present invention orally to a target segment of the GI tract, without having activation of the plasmid before reaching the target segment of the GI tract.
The following is a non-exhaustive list of modulations that can be manipulated with the systems of the present invention.
1. Elimination of harmful bacteria. The cis-conjugative plasmid of the present invention may include a gene or combination of genes that target specific bacteria, within a microbiome, and eliminate said specific bacteria. A non-limiting example of said gene or genes, include the gene that encodes for the TevCas9 nuclease specifically repurposed for killing specific bacteria species within a population of different bacteria species.
2. Augmentation of beneficial microbes in a microbiome. A non-limiting example would be introduction of novel biosynthetic or biodegradative pathways by the cis-conjugative plasmid to enhance growth of the beneficial microbe. A second non-limiting example would be delivery of metabolic capacity to the cis-conjugative plasmid to difficult to cultivate bacteria.
3. Metabolic manipulation of a microbiome by introduction of regulatory sequences by the cis-conjugative plasmid, including but not limited to small RNA molecules and transcription factors, to modulate expression of a gene or genes that are encoded by the target bacteria species that control biosynthesis or degradation of a metabolic product.
Administration
The cis-conjugative plasmid of the present invention is introduced by standard microbiological techniques (plasmid transformation, conjugation, electroporation, transfection, transduction, etc) into a bacterial species, such as a bacterial species that is generally recognized as safe (GRAS). This would include any species that is currently used as a probiotic or used as a food supplement or that can be introduced into an industrial setting or any other environment. The GRAS bacteria is the donor for conjugation of the cis-conjugative plasmid to the microbiome. Administration specifically refers to the bacteria, such as GRAS bacteria, containing the cis-conjugative plasmid that may be administered by a method comprising topically, transdermally, sublingually, rectally, vaginally, ocularly, subcutaneously, intramuscularly, intraperitoneally, urethrally, intranasally, by inhalation or orally. In the instance of non-animal administration, the cis-conjugative plasmid could be introduced as an inoculum into an industrial or environmental system.
In some aspects, the subject is a pediatric patient and the cis-conjugative plasmid is administered in a formulation for the pediatric patient.
In one embodiment, the cis-conjugative plasmid of the present invention is administered locally to the microbial infection.
The cis-conjugative plasmid of the present invention can be concurrently or sequentially administered with other antimicrobial agents and/or surface antigens. In one particular aspect, administration is locally to the site of the infection. Other non-limiting examples of administration include by one or more method comprising transdermally, sublingually, rectally, vaginally, ocularly, intranasally, by inhalation or orally.
Microbial infections and disease that can be treated by the methods of this invention include infection by, for example, Streptococcus agalactiae, Neisseria meningitidis, Treponemes, denticola, pallidum, Burkholderia cepacia or Burkholderia pseudomallei. In one aspect, the microbial infection is one or more of Haemophilus influenzae (nontypeable), Moraxella catarrhalis, Streptococcus pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa, Mycobacterium tuberculosis. These microbial infections may be present in the upper, mid or lower airway (otitis, sinusitis or bronchitis) but also exacerbations of chronic obstructive pulmonary disease (COPD), chronic cough, complications of and/or primary cause of cystic fibrosis (CF) and community acquired pneumonia (CAP).
Infections might also occur in the oral cavity (caries, periodontitis) and caused by Streptococcus mutans, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans. Infections might also be localized to the skin (abscesses, ‘staph’ infections, impetigo, secondary infection of burns, Lyme disease) and caused by Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Borrelia burdorferi. Infections of the urinary tract (UTI) can also be treated and are typically caused by Escherichia coli. Infections of the gastrointestinal tract (GI) (diarrhea, cholera, gall stones, gastric ulcers) are typically caused by Salmonella enterica serovar, Vibrio cholerae and Helicobacter pylori. Infections of the genital tract include and are typically caused by Neisseria gonorrhoeae. Infections can be of the bladder or of an indwelling device caused by Enterococcus faecalis. Infections associated with implanted prosthetic devices, such as artificial hip or knee replacements or dental implants or medical devices such as pumps or monitoring systems, typically caused by a variety of bacteria, can be treated by the methods of this invention. These devices can be coated or conjugated to the cis-conjugative plasmid of the present invention.
Infections caused by Streptococcus agalactiae are the major cause of bacterial septicemia in newborns. Such infections can also be treated by the methods of this invention. Likewise, infections caused by Neisseria meningitidis which can cause meningitis can also be treated.
Thus, routes of administration applicable to the methods of the invention include intranasal, intramuscular, intratracheal, subcutaneous, intradermal, topical application, intravenous, rectal, nasal, oral and other enteral and parenteral routes of administration. Routes of administration may be combined, if desired, or adjusted depending upon the agent and/or the desired effect. The cis-conjugative plasmid of the present invention can be administered in a single dose or in multiple doses. Embodiments of these methods and routes suitable for delivery, include systemic or localized routes. In general, routes of administration suitable for the methods of the invention include, but are not limited to, enteral, parenteral or inhalational routes.
Parenteral routes of administration other than inhalation administration include, but are not limited to, topical, transdermal, subcutaneous, intramuscular, intraorbital, intracapsular, intraspinal, intrasternal and intravenous routes, i.e., any route of administration other than through the alimentary canal. Parenteral administration can be conducted to effect systemic or local delivery of the inhibiting agent. Where systemic delivery is desired, administration typically involves invasive or systemically absorbed topical or mucosal administration of pharmaceutical preparations.
The cis-conjugative plasmid of the present invention can also be delivered to the subject by enteral administration. Enteral routes of administration include, but are not limited to, oral and rectal (e.g., using a suppository) delivery.
Methods of administration of the cis-conjugative plasmid of the present invention through the skin or mucosa include, but are not limited to, topical application of a suitable pharmaceutical preparation, transcutaneous transmission, transdermal transmission, injection and epidermal administration. For transdermal transmission, absorption promoters or iontophoresis are suitable methods. Iontophoretic transmission may be accomplished using commercially available “patches” that deliver their product continuously via electric pulses through unbroken skin for periods of several days or more.
In various embodiments of the methods of the invention, the cis-conjugative plasmid of the present invention will be administered orally on a continuous, daily basis, at least once per day (QD) and in various embodiments two (BID), three (TID) or even four times a day. For example, a minimum of 109 CFU/ml of GRAS species having the cis-conjugative plasmid of the present invention may be administered as a dosage.
Dosing of can be accomplished in accordance with the methods of the invention using capsules, tablets, oral suspension, gel or cream for topical application. In the instance of non-human, non-animal administration, the dosing can be accomplished by suspension, tablets, gel or cream.
The skilled artisan will appreciate that certain factors may influence the dosage and timing required to effectively treat a subject, including but not limited to, the severity of the disease or disorder, previous treatments, the general health and/or age of the subject, and other diseases present. Moreover, treatment of a subject with a therapeutically effective amount of the therapeutic compositions described herein can include a single treatment or a series of treatments.
The compositions and related methods of the present invention may be used in combination with the administration of other therapies. These include, but are not limited to, the administration of DNase enzymes, antibiotics, antimicrobials, or other antibodies.
Kits
Kits containing the agents and instructions necessary to perform in vitro and in vivo methods as described herein also are claimed. Accordingly, the invention provides kits for performing these methods which may include a cis-conjugative plasmid of the present invention as well as instructions for carrying out the methods of this invention such as collecting tissue and/or performing the screen and/or analyzing the results and/or administration of an effective amount of biological agent as defined herein. These can be used alone or in combination with other suitable antimicrobial agents.
In another embodiment, the cis-conjugative plasmid of the present invention can be used in the detection of a target bacteria within a microbiome or biofilm or in the diagnosis of an infectious disease or condition. The guide RNA included in the cis-conjugative plasmid of the present invention may serve to detect a target bacteria in a microbiome or biofilm.
In one embodiment, the present application enables the tracking or detection of Clostridium difficile by transposon-based tagging. The transposon would be delivered by the cis-conjugative plasmid of the present invention and be engineered to only target C. difficile.
The cis-conjugative plasmid of the present invention can be used for tracking uncultivatable bacteria (and also pathogens such as C. difficile) that can be present in very low relative abundance in microbiomes yet have significant contributions to the microbial community. In one embodiment, CRISPR-guided transposons encoded on a cis-conjugative plasmid that would insert only in genes specific to the bacterium of interest. This transposon could encode, for example, a label, such as a fluorescent reporter (such as green fluorescent protein GFP) such that tagged bacteria could be isolated by fluorescent activated cell sorting for downstream attempts at cultivation, or for molecular-based studies as such RNAseq or metagenomics.
The cis-conjugative plasmid of the present invention has numerous potential applications beyond targeted specific bacteria for elimination using CRISPR. The cloning capacity of the cis-conjugative plasmid is very large (at least up to 800 kb sized inserts) meaning that cargo can range from single genes, entire biosynthetic pathways, or whole genomes. As such, the present invention enables the cis-conjugative plasmid for delivery of molecular tools for engineering microbial genomes in situ, for modulating the metabolic output of the human gut microbiome (or any microbiome) by adding additional metabolic capacity, for modulating the expression of existing pathways, or for molecular diagnostic purposes by tracking specific bacteria within complex populations. Any microbiome that is permissible to conjugation is amenable to manipulation through the delivery of genetically-encoded molecular agents. Potential applications could include (but not limited to) modifying the metabolic output of a microbiome, such as the gut microbiome, for increased tolerance to chemotherapeutic agents or tracking the dynamics of pathogens, such as Clostridium difficile, by transposon-based tagging.
These Examples are described solely for purposes of illustration and are not intended to limit the scope of the invention. Changes in form and substitution of equivalents are contemplated as circumstances may suggest or render expedient.
Materials and Methods
Bacterial Strains and Plasmid Construction
E. coli EPI300 (Epicentre) was used for cloning and as a conjugative donor (F′ λ-mcrA Δ(mrr-hsdRMS-mcrBC) ϕ80dlacZ ΔM15 Δ(lac)X74 recA1 endA1 araD139 Δ(ara, leu)7697 galU galK rpsL (StrR) nupG trfA dhfr). Salmonella typhimurium sub. species enterica LT2 (acquired from Dr. David Haniford at Western University) was used as a conjugative recipient strain.
Plasmid Construction.
Plasmids were constructed using a modified yeast assembly. A list of primers is provided. Table 1. The pNuctrans plasmid was constructed by polymerase chain reaction (PCR) amplification of fragments with 60-120 bp homology overlaps from pre-existing plasmids. The oriT fragment was amplified from pPtGE3052 using primers DE-3302 and DE-3303. The p15A origin, chloramphenicol acetyl-transferase gene, and sgRNA cassette was amplified using primers DE-3308 and DE-3309 from a modified pX458 plasmid containing the TevSpCas9 coding region. The TevSpCas9 gene was amplified from the modified pX458 plasmid using primers DE-3306 and DE-3307. The araC gene and pBAD promoter were amplified from pBAD-24 using primers DE-3304 and DE-3305. The CEN6-ARSH4-HIS3 yeast element was amplified from pPtGE30 using primers DE-3316 and DE-3317. S. cerevisiae VL6-48 was grown from a single colony to an OD600 of 2.5-3, centrifuged at 2500×g for 10 min and washed in 50 mL sterile ddH20 and centrifuged. Cells were resuspended in 50 mL of 1M sorbitol, centrifuged, and spheroplasting initiated by resuspending the pellet in 20 mL SPE solution (1M sorbitol, 10 mM sodium phosphate buffer pH 7, 10 mM Na2EDTA pH 7.5) and by adding 30 μL 12M 2-mercaptoethanol and 40 μL zymolyase 20T solution (200 mg zymolyase 20T (USB), 9 mL H2O, 1 mL 1M Tris pH 7.5, 10 mL 50% glycerol) and incubated at 30° C. with shaking at 75 RPM. The yeast was considered spheroplasted once the ratio of the OD600 in sorbitol to the OD600 of yeast in ddH20 reached 1.8-2. Spheroplasts were centrifuged at 1000×g for 5 min before being gently resuspended in 50 mL 1M sorbitol, and centrifuged again. Spheroplasts were then resuspended in 2 mL STC solution (1M sorbitol, 10 mM Tris-HCl pH 7, 10 mM CaCl2)) and incubated at room temperature for 10 min. Pooled DNA fragments at equimolar ratio for each plasmid assembly were gently mixed with 200 μL of spheroplasted yeast and incubated at room temperature for 10 min. A volume of 1 mL of PEG-8000/CaCl2) solution (20% (w/v) PEG 8000, 10 mM CaCl2), 10 mM Tris-HCl, pH 7.5) was added and incubated at room temperature for 20 min before being centrifuged at 1500×g for 7 min. Yeast was resuspended in 1 mL of SOS solution (1M sorbitol, 6.5 mM CaCl2), 0.25% (w/v) yeast extract, 0.5% (w/v) peptone) and incubated at 30° C. for 30 min. The spheroplast solution was added to 8 mL of histidine-deficient regenerative agar (Teknova), poured into a petri dish, and incubated overnight at 30° C. A volume of 8 mL histidine-deficient liquid regenerative media was then added on top of the solidified regenerative agar and grown at 30° C. for 2-5 days. Total DNA was isolated from 1.5 to 3 mL S. cerevisiae using 250 μL buffer P1 (50 mM Tris-HCl pH 8.0, 10 mM EDTA, 100 μg/mL RNase A), 12.5 μL zymolyase 20 T solution and 0.25 μL 12M 2-mercaptoethanol and incubated at 37° C. for 1 h. In total, 250 μL buffer P2 (200 mM NaOH, 1% sodium dodecyl sulfate) was added, incubated at room temperature for 10 min, followed by addition of 250 μL buffer P3 (3.0M CH3CO2K pH 5.5). DNA was precipitated with 700 μL ice-cold isopropanol, washed with 70% ethanol, briefly dried and resuspended in 50 μL sddH2O. The plasmid pool was subsequently electroporated into E. coli EPI300. Individual colonies were screened by diagnostic digest (
The entire nucleic acid sequence of pNuc-cis is provided in Table 3 as SEQ ID NO:27.
Quantitative PCR.
E. coli EPI300 donors and S. enterica transconjugants harboring pNuc-trans and pTA-Mob (trans helper plasmid) or pNuc-cis were grown overnight under selection. sgRNAs were absent from the cis and trans plasmids.
Overnight cultures were diluted 1:50 in selective media and grown to an A600 of ˜0.5. Each culture was diluted, plated on selective LSLB plates (10 g/L tryptone, 5 g/L yeast extract, and 5 g/L sodium chloride, 1% agar), and grown overnight. Colonies were counted manually to determine the CFUs/mL of each culture. At the same time, 500 μL of each culture was pelleted and resuspended in 500 μL 1× phosphate-buffered saline (PBS) and incubated at 95° C. for 10 min before immediate transfer to −20° C. Quantitative real-time PCR was performed on boillysed samples using SYBR Select Master Mix (Applied Biosystems) using primers DE-4635 and DE-4636 that amplified a DNA fragment present on both pNuc-trans and pNuc-cis. Purified pNuc-trans was used as a copy number standard.
Filter Mating Conjugation.
Saturated cultures of donor E. coli EPI300 and recipient S. enterica LT2 were diluted 1:50 into 50 mL nonselective LSLB media. The diluted cultures were grown to an A600 of ˜0.5 and concentrated 100-fold by centrifugation at 4000×g for 10 min. A volume of 200 μL of concentrated donors were mixed with 200 μL concentrated recipients on polycarbonate filters adhered to conjugation plates (LSLB supplemented with 1.5% agar). Conjugation proceeded at 37° C. from 5 min to 24 h. Following conjugation, filters were placed in conical tubes containing 30 mL of 1×PBS (8 g/L NaCl. 0.2 g/L KCl, 1.42 g/L Na2HPO4, 0.24 g/L KH2PO4) and vortexed for 1 min to remove the bacteria from the filter. The supernatant was serially diluted and plated on LSLB plates with selection for donor E. coli EPI300 (gentamicin 40 μg/mL for the cis setup and gentamicin 40 μg/mL, chloramphenicol 25 μg/mL for the trans setup), recipient S. enterica LT2 (kanamycin 50 μg/mL), and transconjugants (kanamycin 50 μg/mL, chloramphenicol 25 μg/mL, 0.2% D-glucose for for pNuc-trans transconjugants or kanamycin 50 μg/mL, gentamicin 40 μg/mL, 0.2% D-glucose for pNuc-cis transconjugants). D-glucoserepresses the expression of TevCas9 in transconjugants. Plates were incubated overnight at 37° C. for 16-20 h. Colonies were counted manually.
S. enterica to S. enterica conjugation.
S. enterica LT2 transconjugants harboring pNuc-cis or pNuc-trans with no sgRNA encoded were obtained from plate conjugation experiments described in detail in the supplementary methods. Transconjugant colonies were grown overnight in LSLB supplemented with kanamycin 50 μg/mL, gentamicin 40 μg/mL and 0.2% D-glucose for pNuc-cis, or kanamycin 50 μg/mL, chloramphenicol 25 μg/mL and 0.2% D-glucose for pNuctrans. S. enterica LT2 was transformed with pUC19 to confer ampicillin resistance for use as a recipient and was grown overnight in LSLB supplemented with kanamycin 50 μg/mL and ampicillin 100 μg/mL. All donor and recipient S. enterica cultures were diluted 1:50 into LSLB and grown to an A600 of 0.5 before spreading 200 μL of each on a conjugation plate supplemented with 0.2% w/v D-glucose to repress TevSpCas9 expression. Conjugations proceeded for 2 h at 37° C. before cells were scraped into 500 μL SOC with a cell spreader. Resulting cell suspensions were serially diluted and plated to select for donors (kanamycin 50 μg/mL, gentamicin 25 μg/mL for pNuc-cis or kanamycin 50 μg/mL, chloramphenicol 25 μg/mL for pNuc-trans), recipient (kanamycin 50 μg/mL, ampicillin 100 μg/mL), and transconjugant (kanamycin 50 μg/mL, gentamicin 40 μg/mL, ampicillin 100 μg/mL for pNuc-cis, chloramphenicol 25 μg/mL, ampicillin 100 μg/mL for pNuc-trans). Plates were incubated at 37° C. for 16-20 h and colonies were counted manually.
Liquid and Bead-Supplemented Conjugation Assays.
E. coli EPI300 and recipient S. enterica LT2 were grown overnight to saturation. Tubes containing 5 mL LSLB supplemented with 0.2% D-glucose were inoculated with 180 μL saturated E. coli and 18 μL saturated S. enterica. Bead-supplemented conjugations were prepared similarly with the addition of 1 mL soda lime glass beads (0.5 mm diameter). Conjugations proceeded by incubating at 37° C. with 0 or 60 RPM agitation for 72 h. Cultures were homogenized by vortexing, serially diluted and spot-plated in 10 μL spots on plates containing appropriate antibiotic selection for donors, recipients, and transconjugants. Plates were incubated at 37° C. for 16-20 h. Colonies were counted manually. Alterations to this protocol were made to determine the effect of donor to recipient ratio (50:1, 10:1, 1:1, 1:10, 1:50), NaCl concentration (2.5, 5, and 10 g/L) and shaking speed (0, 60, and 120 RPM) on conjugation frequency. Killing efficiency assays. Saturated cultures of E. coli EPI300 donors habouring pNuc-trans plasmids encoding sgRNAs and recipient S. enterica LT2 were diluted 1:50 into LSLB supplemented with 0.2% D-glucose. The diluted cultures were grown to an A600 of ˜0.5. 200 μL of each donor was mixed with 200 μL of recipient on a conjugation plate supplemented with 0.2% D-glucose to repress expression of TevCas9. Conjugations proceeded for 1 h at 37° C. before cells were scraped into 500 μL SOC (20 g/L tryptone, 5 g/L yeast extract, 0.5 g/L NaCl, 2.5 mM KCl, 10 mM MgCl2, and 20 mM D-glucose) with a cell spreader. Resulting cell suspensions were serially diluted and plated on selection for donors and recipients in addition to selection for transconjugants with CRISPR repression (kanamycin 50 μg/mL, chloramphenicol 25 μg/mL, 0.2% D-glucose) and transconjugants with CRISPR activation (kanamycin 50 μg/mL, chloramphenicol 25 μg/mL, 0.2% L-arabinose). Plates were incubated overnight at 37° C. for 16-20 h. Killing efficiency is the ratio of cells on selective to nonselective plates.
Escape Mutant Analyses.
Escape mutant colonies were picked from plates selecting for exconjugant S. enterica cells with TevSpCas9 activated after conjugation. These colonies were grown overnight to saturation and plasmids were extracted using the BioBasic miniprep kit. The isolated plasmids were then electroporated into E. coli EPI300 cells and re-isolated for analysis. The plasmids were analyzed by diagnostic restriction digest with FspI and Msil, and by multiplex PCR for the chloramphenicol resistance marker, and a TevSpCas9 gene fragment. Total DNA was isolated using a standard alkaline lysis protocol followed by isopropanol precipitation of the DNA. Potential target sites were PCR amplified from the total DNA sample using Amplitaq 360 (Thermofisher Scientific) and subsequently sequenced.
sgRNA Off-Target Predictions in E. coli.
To predict sgRNA off-target sites, we searched the E. coli genome for sites with less than six mismatches to each sgRNA using a Perl script with an XOR bit search. A mismatch score was calculated that indicates the likelihood of a stable sgRNA/DNA heteroduplex using the formula
where non_seed is a mismatch in the nonseed region of the sgRNA (positions 1-12 from the 5′ end of the target site) and seed is a mismatch in the seed regions (positions 13-20 from the 5′ end of the target site). By this method, mismatches in the 5′ end of sgRNA/DNA heteroduplex are more tolerated than mismatches closer to the PAM sequence. For each sgRNA, we also added a correction for if the adjacent three nucleotides matched the consensus SpCas9 PAM sequence 5′-NGG-3′. Off-target sites with perfect match PAMs were given more weight than offtarget sites with 1 or 2 mismatches. Sample fasta formatted files of sgRNAs (sgRNA.test.fa) and an E. coli genome (MG16552.fna) are also provided. Source code and instructions to execute the perl script are provided in Hamilton et al. (2019) Efficient inter-species conjugative transfer of a CRISPR nuclease for targeted bacterial killing. Nature Communications, 10: 4544. A sample output is shown in
Modeling S. enterica Killing Efficiency.
To model sgRNA parameters that were predictive of S. enterica killing efficiency, we used a generalized linear model in the R statistical language with the formula
sgRNAKE˜sgRNAscore+sgRNAtarget strand+sgRNArepstrand+sgRNAgene func+sgRNAreldist,
where sgRNAKE is the average killing efficiency for a given sgRNA, sgRNAscore is the predicted sgRNA activity score using the algorithm of Guo et al. (Nucleic Acids Res. 46, 7052-7069 (2018)), sgRNAtargetstrand is the transcription strand targeted by the sgRNA (sense or antisense), sgRNArepstrand is whether the sgRNA targets the leading or lagging strand, sgRNAgenefunc is whether the sgRNA targets an essential or non-essential gene in S. enterica, and sgRNAreildist is the position of the sgRNA relative to the AUG codon of the targeted gene. A summary table and graphical output of the model parameters is shown in
Results
Increased Conjugation Frequency with a Cis-Conjugative Plasmid.
We constructed a conjugative plasmid, pNuc, based on the IncP RK2 plasmid to examine parameters that contributed to conjugation (
We used the pNuc-cis and pNuc-trans plasmids to test the hypothesis that the cis setup would support higher levels of conjugation relative to the trans setup in a time-course filtermating assay using E. coli as the donor and S. enterica as the recipient. As shown in
To determine if longer incubation times resulted in higher conjugation frequency with the pNuc-cis system, we used a liquid conjugation assay consisting of low-salt LB (LSLB) media into which varying ratios of donor E. coli and recipient S. enterica cells were added. After 72 h incubation at 37° C. with mild agitation at 60 RPM, we found that high donor to recipient ratios (1:1, 10:1, and 50:1) yielded more transconjugants per recipient than experiments with lower donor to recipient ratios (1:5 or 1:10) (
Collectively, these data show that pNuc-cis has an ˜1000-fold higher conjugation frequency than the pNuc-trans system at 24 h post-mixing because bacteria that receive pNuc-cis become donors for subsequent rounds of conjugation. This would lead to exponentially increasing numbers of conjugative donors in the population. Thus, our data differ significantly from previous studies that concluded that conjugation frequency with a trans system was a limiting factor for CRISPR delivery.
Cell-to-Cell Contact Significantly Increases Conjugation.
The previous experiments demonstrated that pNuc-cis was more efficient at conjugation in a filter mating assay on solid media. With reference to
Interestingly, we observed a reduction in conjugation frequency when a S. enterica specific sgRNA was cloned onto pNuc-cis (the +guide condition) (
S. enterica Killing by Conjugative Delivery of Cas9 and sgRNAsS.
To demonstrate that the TevSpCas9 nuclease could be delivered by conjugation to eliminate specific bacterial species, we designed 65 total sgRNAs targeting 38 essential genes, 23 nonessential genes, and 4 genes with unresolved phenotypes (
We considered a number of variables that would influence sgRNA killing efficiency in S. enterica, including predicted sgRNA activity according to an optimized prokaryotic model41, targeting of the sense or anti-sense strands for transcription, the relative position of the sgRNA in the targeted gene, targeting of the leading or lagging replicative strands, and the essentiality of the targeted gene. Taken independently, no single variable was strongly correlated with sgRNA killing efficiency (
During the course of these experiments, we noted that some sgRNAs were recalcitrant to cloning (
This study shows an IncP RK2 conjugative plasmid to function as a delivery system. This study differs from previous attempts to use conjugation as a delivery system in one key facet—a cis setup where the pNuc plasmid encoded the conjugation machinery as well as the TevCas9 nuclease. The pNuc-cis plasmid of this invention promotes efficient conjugation because ex-conjugants become donors for subsequent re-conjugation, leading to significant increases in conjugation relative to the pNuc-trans plasmid (see
Others have employed strains with the conjugation machinery embedded in the chromosome of the donor bacteria (similar to the pNuc-trans setup), meaning that only a single round of conjugation could occur. In the two-species E. coli-S. enterica used in this study system, it was observed conjugation efficiencies approaching ˜100% with pNuc-cis in culture conditions that promoted cell-to-cell contact and biofilm formation. Because the IncP RK2 system can be conjugated to a wide diversity of bacteria, the cis-conjugation system of the present invention could be used to deliver the TevCas9 nuclease (or other CRISPR nuclease) in complex microbial communities. Anti-CRISPR proteins that are specific for relevant CRISPR systems could also be included on pNUC-cis to prevent acquisition of CRISPR-mediated resistance.
Microbiomes could also be seeded with multiple strains of donor bacteria harbouring versions of pNUC-cis based on different conjugative plasmid backbones (
Microbial communities are complex in terms of bacterial composition and the environments they inhabit. Many human microbial communities exist as biofilms, which presents challenges for delivery of anti-microbial agents. Indeed, a number of disease conditions result from microbial imbalances in mucosal surfaces that are dominated by biofilms. Conjugative plasmids express factors to promote biofilm formation to enhance cell-to-cell contact necessary for formation of the conjugative pilus. By using a donor bacteria that is a native resident of the target microbiome the pNUC-cis plasmid could be introduced to microbial communities more readily than delivery vectors that have difficulty penetrating biofilms. Conversely, other delivery vectors, such as phage-based methods, are better suited to planktonic conditions where conjugation is less efficient.
Depending on the nature of the microbiome and dysbiosis, a combination of conjugative- and phage-based CRISPR delivery systems may also be used.
Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification, improvement and variation of the inventions embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications, improvements and variations are considered to be within the scope of this invention. The materials, methods, and examples provided here are representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention.
The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.
In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.
All publications, patent applications, patents, and other references mentioned herein are expressly incorporated by reference in their entirety, to the same extent as if each were incorporated by reference individually. In case of conflict, the present specification, including definitions, will control.
It is to be understood that while the invention has been described in conjunction with the above embodiments, that the foregoing description and examples are intended to illustrate and not limit the scope of the invention. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2019/051787 | 12/11/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62777869 | Dec 2018 | US |
