PLASMID DISTRIBUTION IN γ-POLYGLUTAMATE-PRODUCING BACILLUS STRAINS ISOLATED FROM "DAN-DOUCHI, " A "NATTO"-LIKE NON-SALTY FERMENTED SOYBEAN FOOD IN CHINA

摘要

Four γ-polyglutamate (γ-PGA)-producing Bacillus strains were isolated from a "dan-douchi" in China, all of which indicated biotin requirement for growth and a considerably high γ-glutamyltranspeptidase (γ-GTP) productivity. These strains carried a single plasmid species, and their molecular sizes and restriction patterns differed completely. Some of HindIII DNA fragments of "dan-douchi" plasmids strongly hybridized with a 1.7-kb TaqI DNA fragment of "natto" plasmid, pUH1, which encodes γ-GTP gene responsible for γ-PGA production, and their molecular sizes of homologous fragments were found to be similar. The hybridization analysis revealed that the structure gene of γ-GTP encoded on "dan-douchi" plasmid was found to greatly resemble that on "natto" plasmid. Furthermore, "dan-douchi" plasmid had a high degree of homology with DNA segment encoding the replication protein of pUH1. These results, therefore, strongly suggest that "dan-douchi" plasmid might be a functional plasmid as well as "natto" plasmid, and it should be considered that both "natto" and "dan-douchi" plasmids might develop from a common ancestral molecule.