The flagella master regulatory gene flhDC of Yersinia pseudotuberculosis serotype III (YPIII) was mutated by deleting the middle region; replaced by a tetracycline resistant gene,; the subsequent mutant strain named YPIIIΔflhDC was obtained. Swimming assay showed that the swimming motility of the mutant strain was completely abolished. The promoter region of the flagella second-class regulatory gene fliA was fused with the lux box,; was conjugated with the mutant; the parent strains respectively for the first cross. LUCY assay result demonstrated that flhDC regulated the expression of fliA in YPIII as reported in E. coli. Biofilm formation of the mutant strain on abiotic; biotic surfaces was observed; quantified. The results showed that mutation of flhDC decreased biofilm formation on both abiotic; biotic surfaces,; abated the infection on Caenorhabdtis elegans. Our results suggest that mutation of the flagella master regulatory gene flhDC not only abolished the swimming motility, but also affected biofilm formation of YPIII on different surfaces. The new function of flhDC identified in this study provides a novel viewpoint for the control of bacterial biofilm formation.
WANG Yao1, DING LiSha1,2, HU YangBo1,2, ZHANG Yong1,2, YANG BaoYu1 & CHEN ShiYun1 1 Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in PAO1. After induction by IPTG for 6 h and 18 h, expression of the aiiA gene in PAO1 completely degraded the quorum sensing autoinducers N-acylhomoserine lactones (AHLs): N-oxododecanoyl-L-homoserine lactone (OdDHL) and N-butyryl-L-homoserine lactone (BHL). The re- duced amount of AHLs in PAO1 was also correlated with decreased expression and production of several virulence factors such as elastase and pyocyanin. AiiA expression also influenced bacterial swarming motility. Most importantly, our studies indicated that aiiA played significant roles in P. aeruginosa biofilm formation and dispersion, as observed by the differences of the biofilm formation on liquid and solid surfaces, and biofilm structures under a scanning electron microscope.
WANG Yao1, DAI Yue1,2, ZHANG Yong1,2, HU YangBo1,2, YANG BaoYu1 & CHEN ShiYun1 1 Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
