RpoS role in virulence and fitness in enteropathogenic Escherichia coli

Abstract

Enteropathogenic Escherichia coli (EPEC) is a diarrheagenic pathogen that afflicts infants in developing countries. The most important virulence trait of EPEC is its ability to intimately adhere to cells in the small intestine, and to elicit diarrhea. The alternative sigma factor RpoS is involved in the virulence of several bacterial species. RpoS coordinates the general stress response and accumulates in cells under stress or in the stationary phase. RpoS levels differ across E. coli strains. High-RpoS strains are highly resistant to environmental stresses, but usually display low nutritional competence, while low-RpoS strains show the opposite phenotype. Here we investigated whether RpoS plays a role in the virulence and fitness of two different EPEC strains, E2348/69 and LRT9. A rpoS null mutation had a small positive effect on LRT9 adherence to epithelial cells, but the expression of the EPEC adhesins BfpA and intimin was not significantly affected by the mutation. E2348/69 adherence was not significantly affected by the rpoS mutation. The intrinsic level of RpoS was higher in LRT9 than in E2348/69 while the latter adhered more strongly and expressed higher levels of the adhesin BfpA than the former. Knockout of rpoS strongly impaired resistance to oxidative, osmotic and acid stress in both E2348/69 and LRT9. However, strain E2348/69 was significantly more sensitive to oxidative stress than LRT9. Finally, competition assays showed that the rpoS mutant of LRT9 displayed higher fitness under continuous culture than its isogenic wild-type strain, while E2348/69 outcompeted its rpoS mutant. In conclusion, RpoS plays mostly a positive role in EPEC biology and at least in the case of strain E2348/69 it is not constrained by the trade-off between vegetative growth and stress resistance.

Role of RpoS in stress resistance, biofilm formation and quorum sensing of Shewanella baltica

“…However, limited information is available regarding the role of RpoS in Shewanella sp. For the stress challenge, S. baltica X7 positively regulated the stress resistance in heat, ethanol and H 2 O 2, as previously reported in other bacterial species such as Y. pseudotuberculosis, E. coli and P. fluorescens (Guan et al 2015;Mata et al 2017;Liu et al 2018). The survival rate was significantly decreased in MrpoS mutant compared to wild type strain of S. baltica after exposure to these stress conditions.…”

“…Some reports have shown that rpoS is also associated with the expression of virulence factor and spoilage potential. For instance, RpoS in E. coli LRT9 positively regulated adherence to epithelial cells (Mata et al 2017). RpoS in Y. pseudotuberculosis regulated the expression of T6SS, flagellum and also biofilm formation through coordinating the synthesis of exopolysaccharides (Guan et al 2015).…”

Function, Evolution, and Composition of the RpoS Regulon in Escherichia coli

“…Other types of E. coli may also show specific niche adaptation involving RpoS. For example, enteropathogenic E. coli (EPEC) (which can cause infant diarrhea), RpoS is, as expected, required for stress resistance but has a differential effect on adherence to epithelial cells that is strain-dependent (Mata et al, 2017).…”

“…While many bacterial gene regulation studies have employed exponential phase cultures, examining bacterial adaptation to stationary phase in laboratory culture may be a useful proxy for understanding how bacteria transition to suboptimal growth conditions in the natural environment. During stationary phase adaptation, the E. coli cell undergoes morphological remodeling (Lange and Hengge-Aronis, 1991), becomes resistant to specific stresses (e.g., heat and oxidative stress; Vidovic et al, 2012;Mata et al, 2017), and substantially reduces overall macromolecule biosynthesis (Yoshida et al, 2018). Translation is down-regulated by the dimerization of ribosomes from the active 70S form to a quiescent 100S form (Yoshida et al, 2019).…”

Modulation ofrpoSfitness by loss ofcpdAactivity during stationary-phase inEscherichia coli

“…Despite its central role in general stress response, rpoS variants with attenuated activity have been observed frequently during prolonged phases of slow growth (8,10,22 ). Strains with attenuated rpoS display an improved ability to utilize poor carbon sources such as succinate and acetate but with a suboptimal stress response, whereas the opposite is true for strains with abundant RpoS (6,8,11,21,(23)(24)(25). Thus, polymorphism at rpoS represent trade off between selfpreservation and nutritional competence (6,8,26).…”