Expression of theEscherichia coliompWcolicin S4 receptor gene is regulated by temperature and modulated by the H-NS and StpA nucleoid-associated proteins

Abstract

The OmpW family consists of a ubiquitous group of small outer membrane (OM) β-barrel proteins of Gram-negative bacteria with proposed roles in environmental adaptation but poorly understood mechanisms of expression. We report here that Escherichia coli K-12 OmpW contents are drastically modified by temperature changes compatible with the leap from the environment to warm-blooded hosts and/or vice versa. Thus, while OmpW is present in the OM of bacteria grown at 37 °C, it sharply disappears at 23 °C with the concomitant acquisition of colicin S4 resistance by the cells. ompW::lacZY fusions indicated that temperature regulation operates at the level of transcription, being ompW expression almost abolished at 23 °C as compared to 37 °C. Moreover, E. coli Δhns mutants lacking H-NS showed reductions in ompW transcription and OmpW contents at 37 °C, indicating positive modulatory roles for this nucleoid-structuring protein in ompW expression. Also, ΔhnsΔstpA double mutants simultaneously lacking H-NS and its paralog StpA showed more severe reductions in ompW expression at 37 °C, resulting in the complete loss of OmpW. The overall results indicate that OmpW contents in E. coli are regulated by both temperature and H-NS and reinforce OmpW functions in bacterial adaptation to warm-blooded hosts.

A Novel Handheld Fluorimeter for Rapid Detection of <italic>Escherichia coli</italic> in Drinking Water

“…Asp116, His117 y Glu120 in that -helix form a charged patch showing a negative-positive-negative charge pattern that is totally complementary to the positive-negative-positive charge pattern of the -helix present in the receptor-binding domain of the bacteriocin colicin S4. This receptor-binding domain is unique, because it doesn't have a homologous sequence in other colicins, so colicin S4 is the only colicin able to bind to OmpW [25]. This fact is responsible for the high specificity of the biosensor method described in this study ( Figure 8).…”

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