Ethanolamine and Choline Promote Expression of Putative and Characterized Fimbriae in Enterohemorrhagic Escherichia coli O157:H7

Abstract

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is an important food-borne pathogen responsible for disease outbreaks worldwide. In order to colonize the human gastrointestinal (GI) tract and cause disease, EHEC must be able to sense the host environment and promote expression of virulence genes essential for adherence. Ethanolamine (EA) is an important metabolite for EHEC in the GI tract, and EA is also a signal that EHEC uses to activate virulence traits. Here, we report that EA influenced EHEC adherence to epithelial cells and fimbrial gene expression. Quantitative reverse transcriptase PCR indicated that EA promoted the transcription of the genes in characterized and putative fimbrial operons. Moreover, putative fimbrial structures were produced by EHEC cells grown with EA but not in medium lacking EA. Additionally, we defined two previously uncharacterized EA-regulated fimbrial operons, loc10 and loc11. We also tested whether choline or serine, both of which are also components of cell membranes, activated fimbrial gene expression. In addition to EA, choline activated fimbrial gene expression in EHEC. These findings describe for the first time the transcription of several putative fimbrial loci in EHEC. Importantly, the biologically relevant molecules EA and choline, which are abundant in the GI tract, promoted expression of these fimbriae. Bacterial pathogens interact directly with mammalian hosts by expressing adhesive structures, or fimbriae, on the outer surfaces of their cells. Fimbriae typically mediate the earliest stages of host colonization and are especially critical for enteric bacteria to successfully colonize the gastrointestinal (GI) tract in order to avoid displacement by the continuous flow of intestinal contents (1, 2). Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a food-borne pathogen that causes bloody diarrhea and hemolyticuremic syndrome worldwide (3). The first step in EHEC pathogenesis involves adherence to the intestinal epithelium and subsequent intimate attachment and formation of attachingand-effacing (AE) lesions on epithelial cells (2). The locus of enterocyte effacement (LEE) pathogenicity island carries most of the genes required for AE lesion formation and intimate attachment to host cells (4). However, factors encoded by genes outside the LEE may also play important roles in EHEC adherence to epithelial cells, especially during the initial stages of EHEC infection (5). The EHEC genome carries 14 to 16 fimbrial loci (6, 7), suggesting that fimbriae are an important component of EHEC's virulence repertoire. However, very little is known about the roles of EHEC fimbriae in colonization of the mammalian GI tract or EHEC's tropism for the large intestine. This is due, at least in part, to the lack of understanding of environmental cues that promote expression of these fimbriae in vitro (2,8,9). Ethanolamine (EA) is an important metabolite for EHEC in the GI tract (10), as well as a cue that EHEC uses to recognize the host environment and modulate expression of virulence...

The Type Three Secretion System 2-Encoded Regulator EtrB Modulates Enterohemorrhagic Escherichia coli Virulence Gene Expression

“…The microarray data indicated that EtrB represses expression of loc11. This locus contains seven ORFs, all of which have been shown to be expressed and cotranscribed (69); therefore, we confirmed the microarray data by measuring expression of the first gene in this operon, Z4498, which is predicted to encode the major fimbrial subunit. Expression of Z4498 was significantly increased in the ⌬etrB strain compared to the level in WT EHEC (Fig.…”

Ethanolamine is a valuable nutrient source that impacts Clostridium difficile pathogenesis

“…Ghose et al, 2016;Pechine and Collignon, 2016). Additionally, a connection between ethanolamine and pilin expression has been reported in Escherichia coli O157:H7 (Gonyar et al, 2014). Neither pilA1 nor fliC expression were impacted by the presence or ability to catabolize ethanolamine ( Fig.…”

“…C. difficile flagella and pilin are detected by the innate immune system and can elicit a response that may impact pathogen clearance or virulence (Pechine et al ., ; Yoshino et al ., ; Maldarelli et al ., ; Batah et al ., ; Ghose et al ., ; Pechine and Collignon, ). Additionally, a connection between ethanolamine and pilin expression has been reported in Escherichia coli O157:H7 (Gonyar et al ., ). Neither pilA1 nor fliC expression were impacted by the presence or ability to catabolize ethanolamine (Fig.…”

A Bacterial Microcompartment Is Used for Choline Fermentation by Escherichia coli 536

“…Two of the choline-positive ECOR strains were isolated from patients with urinary tract infections (UTIs), and three strains were from feces of healthy individuals. We know of no specific connection between choline degradation and E. coli 536 pathogenesis, although choline does induce virulence factors in enterohemorrhagic E coli (76).…”