Substance GIF-2 and process for production of the same

Abstract

A process for producing GIF-2, an antimicrobial peptide, by culturing Bacillus cereus, FERM BP-746, under conditions sufficient to produce GIF-2 and recovering GIF-2 from the culture medium.

Description

THE FIELD OF THE INVENTION

This invention relates to a substance GIF-2 having an antimicrobial activity and to a process for production of the substance.

DESCRIPTION OF THE INVENTION

The inventors of this invention have been undertaking studies on microorganisms which are parasitic to insects and have occasionally found certain bacteria having an antimicrobial activities on organisms. After screening such bacteria, they identified them as bacteria belonging to the species Bacillus cereus. They have continued their studies on the antimicrobial substances produced by the bacteria and isolated a novel substance which they have named GIF-2.

The bacteria which are useful in this invention involve any species of bacteria capable of producing GIF-2. One example of such bacteria is Bacillus cereus SW which was first screened by the inventors and deposited with the Fermentation Research Institute, Japan as International Deposition Acceptance No. FERM BP-746 under the Budapest Treaty. The microbiological characteristics of Bacillus cereus SW are as follows:

______________________________________Gram stain +Spore stain +V-P reaction +Catalase test +Oxidase test +Growth at 50.degree. C. -Heat resistance test (10.degree. C., 30 min.) + (growing)Egg-Yolk reaction +______________________________________

Bacteria such as Bacillus cereus SW are cultured in a suitable media. Some examples of the media are as follows:

______________________________________Medium 1polypepton 3%yeast extract 0.5%NaCl 0.5%deionized water 96% (pH = 7.0)L-mediumbacto-trypton 1%yeast extract 0.5%NaCl 0.5% (pH = 7.0)MY-mediumlactose 1%polypepton 0.5%yeast extract 0.3%malt extract 0.3%(The pH is adjusted to 7.0 with 0.05M phosphoricacid buffer.)______________________________________

In addition to these culture media exemplified above, suitable media such as media for bacteria which contain appropriate amounts of carbon source, nitrogen source, and micronutrients may be used in this invention.

The bacteria may be cultured at 20.degree. to 40.degree. C., preferably at 25.degree. to 30.degree. C. for 2 to 3 days under aerobic conditions such as by shaking culture, aeration culture, stationary culture and the like.

After culturing, the culture medium is centrifuged, for example, at 7,500 rpm for 10 min., to remove bacterial cells. The medium is preferably concentrated if necessary and, after adding calcium chloride to the medium in such an amount as to give 1%, the resulting precipitate is recovered by centrifugation, for example at 2,500 rpm for 10 min. The collected precipitate is dissolved in 100 mM EDTA-0.05M tris-HCl buffer (pH 8.0) and the solution is dialyzed against 0.05M phosphoric acid buffer (pH 7.0). After dialysis, ethanol is added to the dialyzate to give 80%, and the resulting precipitate is then removed. The supernatant is evaporated under reduced pressure to dryness and the residue is dissolved in a deionized water. The pH is adjusted to 3 by addition of hydrochloric acid to form a precipitate. The precipitate is recovered and dissolved in a 0.05M NaHCO.sub.3 aqueous solution, and the solution is dialyzed against deionized water, the dialyzate then being charged into and passed through a column with Sephadex G-100/H.sub.2 O.

Ethanol is added to the eluate solution to give 80% and the mixture in allowed to stand at 4.degree. C. for 2-3 days to give a white crystalline precipitate.

After drying the precipitate under reduced pressure, the product GIF-2 is obtained as white prismatic microcrystals by microscopic observation.

GIF-2 has the following physicochemical properties.

1. Molecular weight: 1057 by Mass spectrometer 2. Color and appearance: White prismatic microcrystals 3. Melting point: 210.degree.-215.degree. C. (light brown, slightly shrunk), 234.degree.-239.degree. C. (dark brown), 240.degree.-245.degree. C. (carbonized) 4. UV absorption spectrum: Shown in FIG. 1 measured as a 2.8% aqueous solution 5. IR spectrum: Shown in FIG. 2 6. Solubilities in solvents: Soluble in water, methanol, ethanol, and t-butanol; insoluble in n-butanol, acetone, ethyl acetate, ether, chloroform, benzene, carbon tetrachloride, and petroleum ether 7. Color change test: ______________________________________ CBB test + Xanthoprotein test + Adamkiewitz test - Earlich test - Biuret test +______________________________________ 8. Other property: A solution of this substance in water (1.4 mg/ml) has a pH of 7.6 9. Amino acid composition: The amino acid composition by an amino acid analyzer is as follows: ______________________________________ Amino Moler acid ratio______________________________________ AsX 2 Ser 1 GlX 1 Leu 1 Tyr 1 Pro 1______________________________________ wherein one of three X's has an amido bond, and in addition to the above amino acids, one molecule of .beta.-amino acid is found by a mass spectrometer. 10. Presumed Structure: ##STR1## wherein one of three X's is an amido bond and R is a .beta.-amino acid residue represented by the formula

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a chart showing U.V. absorption spectrum of GIF-2, and

FIG. 2 is a chart showing I.R. absorption spectrum of GIF-2.

The antimicrobial activities of GIF-2 are confirmed and shown hereunder.

The antimicrobial activities in relation to various microorganisms were tested by the use of the following culture media and the results are shown in Tables 1 to 4 below.

______________________________________Culture medium for bacteria in generalMeat extract 10 gPeptone 10 gNaCl 5 gWater 1 l (pH = 7.2)Culture medium for mycobacteriaGlycerol 10 gPolypepton 10 gCasamino acid 5 gYeast extract 5 gNa.sub.2 HPO.sub.4 0.5 gWater 1 l (pH = 7.2)Culture medium for fungiLactose 10 gPolypepton 5 gYeast extract 3 gMalt extract 3 g0.05M phosphoric acid buffer 1 l (pH = 7.0)______________________________________ The following microorganisms were cultured on a microtiter plate at 27.degree. C. for 3 to 7 days. The minimum inhibitory concentration (MIC) of GIF-2 with respect to the microorganisms is shown in Tables 1 to 4 below. TABLE 1______________________________________Strain M.I.C.(.mu.g/ml)______________________________________Bacillus subtilis IAM 1206 > 625 IAM 1069 > 625 IAM 1145 > 625 IAM 1168 > 625 IAM 1169 > 625 IAM 1207 > 625 IAM 1212 > 625 IAM 1213 > 625 IAM 1259 > 625 IAM 1260 > 625 IAM 11060 > 625 IAM 12021 > 625 IAM 12118 > 625Bacillus licheniformis IAM 11054 > 625Bacillus polymixa IAM 1210 > 625Bacillus amyloliquefaciens IAM 1521 > 625Bacillus cereus IAM 1029 > 625 IAM 1072 > 625 IAM 1110 > 625 IAM 1656 > 625 IAM 1729 > 625Bacillus coagulans IAM 1194 > 625Bacillus megaterium IAM 1166 19Bacillus cereus SW > 625______________________________________ TABLE 2______________________________________Strain M.I.C.(.mu.g/ml)______________________________________Escherichia coli IAM 1268 > 625Enterobacter aerogenes IAM 12348 > 625Klebsiella pneumoniae IAM 1063 > 625Serratia marcescens IAM 12142 > 625Proteus vulgaris IAM 1025 > 625Pseudomonas aeruginosa PAO 1 > 625Staphylococcus aureus NIHJ 209P > 625Micrococcus luteus IAM 1056 > 625Arthrobacter nicotianae IAM 12342 > 625Nocardia opaca IAM 12123 > 625Mycobacterium phlei AU 3368 > 625Mycobacterium phlei AU 1574 > 625______________________________________ TABLE 3______________________________________Strain M.I.C.(.mu.g/ml)______________________________________Conidiobolus lamprauges sp. No. 454 19.5 ATCC 28996 39 ATCC 28997 19.5 CBS 153 19.5Conidiobolus thromboides ATCC 12587 39Conidiobolus nanodes CBS 154 19.5Conidiobolus nanodes CBS 183 19.5Conidiobolus chlamydosporus CBS 167 39Fusarium oxysporum IAM 5009 39______________________________________ TABLE 4______________________________________Strain M.I.C.(.mu.g/ml)______________________________________Aspergillus fumigatus IAM 2004 78Aspergillus nidulans IAM 2006 39Aspergillus oryzae IAM 2640 156Chaetomium globosum IAM 8059 78Eurotium chevalieri IFO 4928 19.5 ATCC 16496 39Gliocladium virens IAM 5061 39Mucor rouxianus IAM 6131 78Mucor javanicus IAM 6087 156Myrothecium verrucaria IAM 5063 78Penicillium chrysogenum IAM 7106 39Cryptococcus luteolus IAM 12207 19.5Debaryomyces castellii IAM 4977 78Hansenula anomala IAM 4967 39Hansenula wingei IAM 4983 19.5Kloeckera africana IAM 4984 39Saccharomyces cerevisiae IAM 4125 39Torulopsis colliculosa IAM 4188 39______________________________________

This invention is further illustrated by the following Example.

EXAMPLE

The strain Bacullus cereus SW, FERM BP-746 was inoculated on Medium 1 described above and cultured at 27.degree. C. for 3 days by shaking culture.

The resulting culture medium was centrifuged at 7,500 rpm for 10 min., and to the supernatant was added calcium chloride to give 1%. The resulting precipitate was recovered by centrifugation at 2,500 rpm for 10 min. The precipitate was dissolved in a 100 mM EDTA-0.05M tris-HCl buffer (pH 8.0) and the solution was dialyzed against a 0.05M phosphoric acid buffer, and ethanol was added to the dialyzed solution to give a final concentration of 80%.

The resulting precipitate was removed, the supernatant was evaporated under reduced pressure to dryness and the residue was dissolved in deionized water. The pH of the solution was then adjusted to 3 by addition of hydrochloric acid. The resulting precipitate was dissolved in a 0.05M NaHCO.sub.3 aqueous solution and the solution was dialyzed against deionized water. The dialyzate solution was then charged into and passed through a column with Sephadex G-100/H.sub.2 O. Ethanol was added to the eluate to give a concentration of 80%, and the mixture was allowed to stand at 4.degree. C. for 2 to 3 days to form a white crystalline precipitate.

The precipitate was evaporated under reduced pressure, to dryness and the presence of GIF-2 was confirmed as white prismatic microcrystals by microscopic observation.

Claims

1. A process for producing the substance GIF-2 which comprises culturing bacteria capable of producing GIF-2 and belonging to species Bacillus cereus Ferm BP-746 under conditions sufficient to produce GIF-2 and recovering GIF-2 from the culture medium.