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

Four gamma-polyglutamate (gamma-PGA)-producing Bacillus strains were isolated from a ''dan-douchi'' in China, all of which indicated biotin requirement for growth and a considerably high gamma-glutamyltranspeptidase (gamma-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 gamma-GTP gene responsible for gamma-PGA production, and their molecular sizes of homologous fragments were found to be similar. The hybridization analysis revealed that the structure gene of gamma-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.