Comparative analysis of sigma factors RpoS, FliA and RpoN in Edwardsiella tarda

Sigma factors are important regulators that bacteria employ to cope with environmental changes. Studies on the functions of sigma factors have uncovered their roles in many important cellular activities, such as growth, stress tolerance, motility, biofilm formation, and virulence. However, comparative analyses of sigma factors, which examine their common and unique features or elucidate their cross-regulatory relationships, have rarely been conducted for Edwardsiella tarda. Here, we characterized and compared motility and resistance to oxidative stress of E. tarda strains complemented with rpoS, fliA, and rpoN mutants. The results suggest that the sigma factors, FliA and RpoN, regulated motility, whereas RpoS exhibited no such function. RpoS and RpoN were essential for oxidative stress resistance, whereas FliA had no obvious impact under oxidative stress conditions. Furthermore, 2-dimensional gel electrophoresis (2-DE) based proteomics analysis, combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS/MS), revealed 12 differentially expressed protein spots that represented 11 proteins between the mutant and wild-type strains. Quantification of the expression of target genes by quantitative reverse transcription PCR (qRT-PCR) confirmed the results of our proteomics analysis. Collectively, these results suggest that these sigma factors are multi-functional mediators involved in controlling the expression of many metabolic pathway genes.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author