The role of periplasmic antioxidant enzymes (superoxide dismutase and thiol peroxidase) of the Shiga toxin-producingEscherichia coli O157:H7 in the formation of biofilms

Abstract

This study examined the role of the periplasmic oxidative defense proteins, copper, zinc superoxide dismutase (SodC), and thiol peroxidase (Tpx), from the Shiga toxin-producing Escherichia coli O157:H7 (STEC) in the formation of biofilms. Proteomic analyses have shown significantly higher expression levels of both periplasmic antioxidant systems (SodC and Tpx) in STEC cells grown under biofilm conditions than under planktonic conditions. An analysis of their growth phase-dependent gene expression indicated that a high level of the sodC expression occurred during the stationary phase and that the expression of the tpx gene was strongly induced only during the exponential growth phase. Exogenous hydrogen peroxide reduced the aerobic growth of the STEC sodC and tpx mutants by more than that of their parental strain. The two mutants also displayed significant reductions in their attachment to both biotic (HT-29 epithelial cell) and abiotic surfaces (polystyrene and polyvinyl chloride microplates) during static aerobic growth. However, the growth rates of both wild-type and mutants were similar under aerobic growth conditions. The formation of an STEC biofilm was only observed with the wild-type STEC cells in glass capillary tubes under continuous flow-culture conditions compared with the STEC sodC and tpx mutants. To the best of our knowledge, this is the first mutational study to show the contribution of sodC and tpx gene products to the formation of an E. coli O157:H7 biofilm. These results also suggest that these biofilms are physiologically heterogeneous and that oxidative stress defenses in both the exponential and stationary growth stages play important roles in the formation of STEC biofilms.

The LysR-Type Transcriptional Regulator LeuO Controls Expression of Several Genes in Salmonella enterica Serovar Typhi

“…The proteins identified in this study thus corresponded to outer membrane proteins, such as OmpS1, OmpS2, and OmpX (11,12,33); to proteins involved in detoxification, such as Tpx and AssT (20,22,24); and to the hypothetical STY1978 and STY3068 proteins (41). Previously, we described isolation, characterization, and regulation analysis of the quiescent porins OmpS1 and OmpS2; furthermore, we showed that the genes encoding these proteins are LeuO targets, and thus we considered these proteins relevant controls for proteomic analysis.…”

“…Inactivation of ompX increased tolerance to sodium dodecyl sulfate and antibiotic compounds, suggesting that OmpX affects transport of hydrophobic compounds across the membrane (40). The tpx gene was also negatively regulated by LeuO; this gene is proposed to code for a periplasmic antioxidant enzyme that is induced under several pH conditions (51), in the exponential growth phase, and during biofilm formation (22). STY1978 is another LeuO-dependent gene, and it encodes a hypothetical protein with no assigned functional role (41).…”

Roles of the Extraintestinal Pathogenic Escherichia coli ZnuACB and ZupT Zinc Transporters during Urinary Tract Infection

“…Zinc protects against iron-triggered membrane lipid oxidation (30,58), which may partially explain why Znu-and ZupT-mediated zinc transport may provide resistance to oxidative stress. One explanation for increased sensitivity to hydrogen peroxide may be due to lowered activity or decreased expression of the E. coli SodC, Zn/Cu superoxide dismutase.…”

“…One explanation for increased sensitivity to hydrogen peroxide may be due to lowered activity or decreased expression of the E. coli SodC, Zn/Cu superoxide dismutase. In E. coli SodC has been shown to contribute to increased resistance to H 2 O 2 (23,30), and zinc ions have been shown to be required for stable binding of copper to the SodC catalytic site (2). In S. enterica serovar Typhimurium, Ammendola et al (2) recently reported that zinc limitation and the loss of ZnuA resulted in a decreased level of expression of SodCII, which is the Salmonella ortholog of E. coli SodC.…”

Inhibitory effects of the κ-casein macropeptide isolated from milk protein on the biofilm formation and virulence of Listeria monocytogenes

“…Protein samples were precipitated by using the phenol protocol. 20) The protein concentration was determined by using the modified Bradford assay method.…”