Appl Environ Microbiol. 1996 Nov;62(11):4081-5. doi: 10.1128/aem.62.11.4081-4085.1996.
Bacillus subtilis RB14, which showed antibiotic activities against several phytopathogens in vitro by producing the antibiotics iturin A and surfactin, was subjected to a pot test to investigate its ability to suppress damping-off of tomato seedlings caused by Rhizoctonia solani. To facilitate recovery from soil, B. subtilis RB14-C, a spontaneous streptomycin-resistant mutant of RB14, was used. Damping-off was suppressed when the culture broth, cell suspension, or cell-free culture broth of RB14-C was inoculated into soil. Iturin A and surfactin were recovered from the soils inoculated with the cell suspension of RB14-C, confirming that RB14-C produced them in soil. The gene lpa-14, which was cloned from RB14 and required for the production of both antibiotics, was mutated in RB14-C, and a mutant, R(Delta)1, was constructed. The level of disease suppressibility of R(Delta)1 was low, but R(Delta)1(pC115), a transformant of R(Delta)1 with the plasmid pC115 carrying lpa-14, was restored in suppressibility. These results show that the antibiotics iturin A and surfactin produced by RB14 play a major role in the suppression of damping-off caused by R. solani. RB14-C, R(Delta)1, and R(Delta)1(pC115) persisted in soil during the experimental period and were recovered from the soil, mostly as spores.
枯草芽孢杆菌 RB14 能够产生抗生素伊枯草菌素 A 和表面活性剂，对几种植物病原菌具有体外抗菌活性，因此进行了盆栽试验以研究其抑制由立枯丝核菌引起的番茄幼苗猝倒病的能力。为了便于从土壤中回收，使用了 RB14 的自发链霉素抗性突变体 RB14-C。当将 RB14-C 的培养液、细胞悬浮液或无细胞培养液接种到土壤中时，猝倒病得到了抑制。从接种了 RB14-C 细胞悬浮液的土壤中回收了伊枯草菌素 A 和表面活性剂，证实 RB14-C 在土壤中产生了它们。从 RB14 中克隆的、对两种抗生素的产生都必需的基因 lpa-14 在 RB14-C 中发生了突变，并构建了一个突变体 R(Delta)1。R(Delta)1 的疾病抑制水平较低，但携带 lpa-14 的质粒 pC115 的转化体 R(Delta)1(pC115)恢复了抑制能力。这些结果表明，RB14 产生的抗生素伊枯草菌素 A 和表面活性剂在抑制由立枯丝核菌引起的猝倒病方面发挥了主要作用。在实验期间，RB14-C、R(Delta)1 和 R(Delta)1(pC115)在土壤中持续存在，并从土壤中回收，主要是作为孢子。
