Role of rpoS in Escherichia coli O157:H7 Strain H32 Biofilm Development and Survival

Abstract

bThe protein RpoS is responsible for mediating cell survival during the stationary phase by conferring cell resistance to various stressors and has been linked to biofilm formation. In this study, the role of the rpoS gene in Escherichia coli O157:H7 biofilm formation and survival in water was investigated. Confocal scanning laser microscopy of biofilms established on coverslips revealed a nutrient-dependent role of rpoS in biofilm formation, where the biofilm biomass volume of the rpoS mutant was 2.4-to 7.5-fold the size of its rpoS ؉ wild-type counterpart in minimal growth medium. The enhanced biofilm formation of the rpoS mutant did not, however, translate to increased survival in sterile double-distilled water (ddH 2 O), filter-sterilized lake water, or unfiltered lake water. The rpoS mutant had an overall reduction of 3.10 and 5.30 log 10 in sterile ddH 2 O and filter-sterilized lake water, respectively, while only minor reductions of 0.53 and 0.61 log 10 in viable counts were observed for the wild-type form in the two media over a 13-day period, respectively. However, the survival rates of the detached biofilm-derived rpoS ؉ and rpoS mutant cells were comparable. Under the competitive stress conditions of unfiltered lake water, the advantage conferred by the presence of rpoS was lost, and both the wild-type and knockout forms displayed similar declines in viable counts. These results suggest that rpoS does have an influence on both biofilm formation and survival of E. coli O157:H7 and that the advantage conferred by rpoS is contingent on the environmental conditions.

Comparative gene expression analysis of Porphyromonas gingivalis ATCC 33277 in planktonic and biofilms states

“…Similar results have been reported for E . coli [61]. Besides, members of the AraC family of transcriptional regulators (PGN_0082), with decreased expression in the biofilm, have been shown to be important in carbon metabolism (degradation of sugars such as arabinose), stress response to virulence in other species [62], and in the regulation of quorum sensing signaling in P .…”

Elucidating the Function of the RpoS Regulon

“…RpoS-dependent increases in csgD overcome this control and allow biofilm formation [58]. Balancing this antagonistic control may be markedly affected by the nature of the bacterial strain tested and by culture conditions -RpoS has been found to be a negative [59,60] and positive [61] regulator of factors affecting biofilm formation depending on experimental context [62]. Further complicating analysis, expression of rpoS [63] and csgD [64] among cells within biofilms is heterogeneous and this is likely important in biofilm formation and differentiation.…”

Escherichia coli YmdB regulates biofilm formation independently of its role as an RNase III modulator

“…Moreover, among the YmdB-modulated genes, ten are reported to be related to biofilm formation, the presence of which is a universal feature of bacteria and a component of multicellular communities [22]. Biochemical analyses indicate that induction of YmdB strongly inhibits biofilm formation in a manner similar to that of RpoS, which is a regulator of general stress responses [20] and a biofilm inhibitor [23][24][25]. Inhibition occurred via two mechanisms that were either dependent or independent of RNase III activity.…”