生防菌Bs-916突变菌株M49芽胞形成和感受态形成能力

Sporulation, competence development and biopesticide activity of a Bacillus subtilis mutant

摘要:

摘要：生防枯草芽胞杆菌Bs-916（Bacillus subtilis）在水稻纹枯病的防治上效果显著。应用离子注入突变对Bs-916进行了突变，获得了一系列的突变菌株。其中突变菌株M49，其表面活性素Surfactin分泌量比出发菌株Bs-916大大降低并导致其防效降低。【目的】为了确认影响该菌株防效降低的影响因子，对其表型和相关基因表达水平进行了研究。【方法】应用生孢培养基，通过芽胞形成能力评测方法比较该菌株和野生菌株Bs-916的芽胞形成能力；通过转化质粒的实验评测突变菌株M49和野生型Bs-916的

Abstract:

Abstracts: Biocontrol Bacillus subtilis strain Bs-916 has obvious effects against Rhizoctonia solani. We demonstrated that the mutant strain, M49 obtained by means of low energy ion implantation in strain Bs-916, which produces significantly lower levels of surfactin, had no obvious effects against R. solani. [Objective] In order to identify the influencing factors of surfactin-decrease mutant strain M49, its phenotype and related gene expression levels were studied. [Methods] Strains to be tested for sporulation were grown for 24 h in sporulation medium. Plasmid pDG1728(1 μg/mL) was used for DNA transformation to test competence development of M49 and Bs-916 strains. RT-PCR (Semi-quantitative reverse transcriptase-polymerase chain-reaction) was used to determine the expression levels of selected genes involved in competence and sporulation in both the wildtype Bs-916 and mutant M49 strains, such as comS, rapA, rapC gene. [Results] Our data showed that mutant strain M49 confers a leaky competence phenotype, typified by a ten-fold reduction. This indicated a fact that DNA fragments are more easily transformed to wildtype strain than M49 mutant. The M49 strain also appeared to exhibit a sporulation-deficient phenotype, compared with the wild-type Bs-916, its spore’s number declined by about 75%. RT-PCR results showed that both the comS and rapC genes were expressed in the Bs-916 strain but not in the M49 strain. [Conclusions] These results indicate that surfactin production, spore formation and competence development of Bacillus subtilis mutant strain M49 are severely decreased. And then, our data implicated that the cause of spore formation and antifungal activity may be the mutation of three key amino acids in ComA protein.