The expression of Longus type 4 pilus of enterotoxigenic Escherichia coli is regulated by LngR and LngS and by H‐NS, CpxR and CRP global regulators

Abstract

Enterotoxigenic Escherichia coli produces a long type 4 pilus called Longus. The regulatory elements and the environmental signals controlling the expression of Longus-encoding genes are unknown. We identified two genes lngR and lngS in the Longus operon, whose predicted products share homology with transcriptional regulators. Isogenic lngR and lngS mutants were considerably affected in transcription of lngA pilin gene. The expression of lngA, lngR and lngS genes was optimally expressed at 37°C at pH 7.5. The presence of glucose and sodium chloride had a positive effect on Longus expression. The presence of divalent ions, particularly calcium, appears to be an important stimulus for Longus production. In addition, we studied H-NS, CpxR and CRP global regulators, on Longus expression. The response regulator CpxR appears to function as a positive regulator of lng genes as the cpxR mutant showed reduced levels of lngRSA expression. In contrast, H-NS and CRP function as negative regulators since expression of lngA was up-regulated in isogenic hns and crp mutants. H-NS and CRP were required for salt- and glucose-mediated regulation of Longus. Our data suggest the existence of a complex regulatory network controlling Longus expression, involving both local and global regulators in response to different environmental signals.

The CpxRA stress response system regulates virulence features of avian pathogenic Escherichia coli

“…The regulatory role of the CpxRA TCS in the expression of several pili of pathogenic E. coli including the BFP, curli, P pili, and Longus has been well-documented (Hung et al, 2001;Hernday et al, 2004;Nevesinjac and Raivio, 2005;De la Cruz et al, 2017). It is not surprising that biofilm was affected in the ΔcpxA mutant since production of T1F and flagella were also affected and these components contribute significantly to biofilm formation.…”

“…The mutation of cpxRA in enteropathogenic E. coli (EPEC) affects the production of type IV bundle-forming pili, impairing adherence to epithelial cells (Nevesinjac and Raivio, 2005), while an enterohemorragic E. coli (EHEC) O157:H7 cpxA mutant is defective in cell adherence due to the alteration in the secretion of type 3 secretion effectors and components (De la Cruz et al, 2016). The production of Longus, a type IV pilus of enterotoxigenic E. coli, was recently demonstrated to be regulated by the CpxRA TCS (De la Cruz et al, 2017).…”

“…A variety of potential virulence determinants associated with survival, fitness, and pathogenesis of APEC strains has been reported. These include, fimbrial and non-fimbrial adhesins involved in colonization of the trachea and the lung such as type 1 fimbriae, curli, P fimbriae, the Stg and Yqi fimbriae, type IV pili, the E. coli common pilus (ECP), the temperature-sensitive hemagglutinin Tsh and proteins involved in invasion (IbeA and Tia) (Dozois et al, 2000;Stacy et al, 2014;De la Cruz et al, 2017). It was previously shown in in vitro and in vivo experiments that the absence of the IbeA invasin affects the ability of APEC to invade human brain microvascular endothelial cells (HBMEC) (Germon et al, 2005).…”

Two Type VI Secretion Systems of Enterobacter cloacae Are Required for Bacterial Competition, Cell Adherence, and Intestinal Colonization

“…This work represents the first investigation of the T6SS function in the Enterobacter genus and it describes the different roles of two T6SS in the pathogenicity of E. cloacae ATCC 13047. Several studies have demonstrated that environmental conditions are important for the differential expression of genes involved in the bacterial virulence (Dong and Mekalanos, 2012;Blair et al, 2013;De La Cruz et al, 2017;Ares et al, 2019). We showed that TSB and DMEM growth media stimulated the expression of E. cloacae T6SS-1 and T6SS-2, respectively, indicating that gene expression in both T6SSs is regulated by specific environmental cues, most likely compounds present in the culture medium.…”

The Coli Surface Antigen CS3 of Enterotoxigenic Escherichia coli Is Differentially Regulated by H-NS, CRP, and CpxRA Global Regulators

“…Host and environmental stimuli such as temperature, osmolarity, pH, and carbon source are sensed by ETEC to regulate the expression of virulence factors such as toxins and pili (Kansal et al, 2013; Munson, 2013; Haycocks et al, 2015; De La Cruz et al, 2017). However, only in a few cases the influence of environmental and nutritional factors on the expression and production of some of the ETEC’s CFs has been reported.…”