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

Abstract

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 that 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 based proteomics analysis combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry 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 confirmed the results of our proteomics analysis. Collectively, these results suggest that these sigma factors are multifunctional mediators involved in controlling the expression of many metabolic pathway genes.

Essential Role of σ Factor RpoF in Flagellar Biosynthesis and Flagella-Mediated Motility of Acidithiobacillus caldus

“…The assembly and function of bacterial flagella generally require dozens of genes that encode structural subunits, regulatory proteins, motor force generators and the chemosensory system (Chen et al, 2011; Fitzgerald et al, 2014; Zhao et al, 2014; Osterman et al, 2015). These genes are organized into a large complex cluster in some bacteria, and are regulated hierarchically at transcriptional level via diverse regulatory systems (Dasgupta et al, 2000; Jacobi et al, 2004; Schulz et al, 2012; Galeva et al, 2014; Song et al, 2016). RpoF (σ 28 or FliA) is one of the σ factors that regulates the synthesis of filaments and attracts wide attentions in various bacterial species, including Legionella pneumophila (Schulz et al, 2012), E. coli (Kundu et al, 1997), P. aeruginosa (Starnbach and Lory, 1992).…”