title: Rifampicin-Resistance Mutations in therpoBGene inBacillus velezensisCC09 have Pleiotropic Effects.
abstract: Rifampicin resistance (Rifr) mutations in the RNA polymerase β subunit (rpoB) gene exhibit pleiotropic phenotypes as a result of their effects on the transcription machinery in prokaryotes. However, the differences in the effects of the mutations on the physiology and metabolism of the bacteria remain unknown. In this study, we isolated seven Rifrmutations inrpoB, including six single point mutations (H485Y, H485C, H485D, H485R, Q472R, and S490L) and one double point mutation (S490L/S617F) from vegetative cells of an endophytic strain,Bacillus velezensisCC09. Compared to the wild-type (WT) strain (CC09), the H485R and H485D mutants exhibited a higher degree of inhibition ofAspergillus nigerspore germination, while the H485Y, S490L, Q472R, and S490L/S617F mutants exhibited a lower degree of inhibition due to their lower production of the antibiotic iturin A. These mutants all exhibited defective phenotypes in terms of pellicle formation, sporulation, and swarming motility. A hierarchical clustering analysis of the observed phenotypes indicated that the four mutations involving amino acid substitutions at H485 in RpoB belonged to the same cluster. In contrast, the S490L and Q472R mutations, as well as the WT strain, were in another cluster, indicating a functional connection between the mutations inB. velezensisand phenotypic changes. Our data suggest that Rifrmutations cannot only be used to study transcriptional regulation mechanisms, but can also serve as a tool to increase the production of bioactive metabolites inB. velezensis.
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Xun-Chao
authors.initials: XC
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Xi
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Jia-Dong
authors.initials: JD
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Chang-Hong
authors.initials: CH
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University Nanjing, China.
authors.forename: Ya-Rong
authors.initials: YR
authors.lastname: Xue
authors.affiliation: Institute of Food Safety and Inspection - Jiangsu Academy of Agricultural Sciences Nanjing, China.
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Yu
keywords: Bacillus velezensis; RNA polymerase; iturin A; mutation; rifampicin resistance