Persistence of Bacillus subtilis RB14 and Its Derivative Strains in Soil with Respect to the lpa-14 Gene

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Bacillus subtilis RB14 produces the antibiotics iturin A and surfactin, and expresses broad suppressibility against several phytopathogenic microorganisms. The gene lpa-14,cloned from RB14,is responsible for the production of both antibiotics. In this study, the contribution of lpa-14 to the persistence of strain RB14 or its derivative strains in soil was investigated. Strain RB14-C is a spontaneous streptomycin-resistant mutant of RB14. When its survival in soil was examined at 30℃, immediately after the inoculatioin of vegetative cells, rapid sporulation occurred until the cell population was stabilized as spores at a level of over 10^7 cfu/g-dry soil. At the same temperature, both R△1,a mutant in which lpa-14 was deleted, and R△1(pC115), a transformant in which antibiotic productivity was restored by transforming R△1 with a plasmid carrying lpa-14,showed similar soil population dynamics to those of RB14-C. At 15℃, although the rate of decline in the total cell number and the sporulation rate of RB14-C were significantly reduced, the numbers of cells in the soil was finally stabilized at the same level as at 30℃. However, R△1 cells were stabilized at a much lower level at 15℃, mainly due to a higher death rate of vegetative cells and a slower sporulation rate. This was especially significant in non-sterile soil, presumably due to a reduced ability to compete with indigenous soil microflora caused by the loss of iturin A and surfactin production. In the case of R△1(pC115), the survival rate of vegetative cells and sporulation ability at 15℃ were not completely restored to the levels of those of RB14-C. The results showed that lpa-14 was associated not only with the production of lipopeptides but also with survival of vegetative cells and the decline of the sporulation rate at 15℃.
社団法人日本生物工学会の論文
1996-01-25

Persistence of Bacillus subtilis RB14 and Its Derivative Strains in Soil with Respect to the lpa-14 Gene

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