Expression of the Yersinia enterocolitica O:3 LPS O-antigen and outer core gene clusters is RfaH-dependent

Abstract

The antiterminator RfaH is required for the expression of LPS, capsule, haemolysin, exotoxin, haemin uptake receptor and F pilus. As these structures are critical for bacterial virulence, loss of RfaH usually leads to attenuation. Here, we inactivated the rfaH gene of Yersinia enterocolitica O:3 to study its role in this enteropathogen. RNA sequencing of the WT and DrfaH strain transcriptomes revealed that RfaH acted as a highly specific regulator that enhanced the transcription of the operons involved in biosynthesis of LPS O-antigen and outer core (OC), but did not affect the expression of enterobacterial common antigen. Interestingly, the transcriptome of the DrfaH strain was very similar to that of an O-antigen-negative mutant. This indicated that some of the changes seen in the DrfaH strain, such as the genes involved in outer membrane homeostasis or in the stress-response-associated Cpx pathway, were actually due to indirect responses via the loss of O-antigen. The decreased amount of LPS on the DrfaH strain cell surface resulted in an attenuated stress response, and lower resistance to compounds such as SDS and polymyxin B. However, the DrfaH strain was significantly more resistant to complement-mediated killing by normal human serum. Taken together, our results revealed a novel role of RfaH acting as a highly specific regulator of O-antigen and OC of LPS in Y. enterocolitica O:3. It may be speculated that RfaH might have an in vivo role in controlling tissue-specific expression of bacterial surface oligo/polysaccharides.

Fis Is Essential for Yersinia pseudotuberculosis Virulence and Protects against Reactive Oxygen Species Produced by Phagocytic Cells during Infection

“…RfaH has been characterized as a global regulator of LPS synthesis in several gram-negative organisms, including Y . enterocolitica , where deletion of this gene results in a “rough” phenotype, in which core inner core LPS is exposed [ 69 ]. In Y .…”

Capsular polysaccharide production and serum survival of Vibrio vulnificus are dependent on antitermination control by RfaH

“…Mutations in the rfaH gene generally result in attenuation but the specific effects on virulence‐related functions can vary. For example, while an rfaH mutant of uropathogenic Escherichia coli showed an altered LPS phenotype, produced less K15 capsule and alpha hemolysin, and was less resistant to human serum , a Yersinia enterocolitica rfaH mutant produced less LPS and was attenuated in its stress response, but was more resistant to serum killing .…”

Differential impact of lipopolysaccharide defects caused by loss of RfaH in Yersinia pseudotuberculosis and Yersinia pestis

“…For instance, a Y . enterocolitica Δ rfaH mutant was shown to have greater sensitivity to polymyxin, but more resistance to serum complement 21 . We also previously identified rfaH in a screen for Yptb IP32953 mutants with increased antimicrobial chemokine binding 18 suggesting a role for RfaH in bacterial colonization.…”

“…Loss of RfaH in Y . enterocolitica serotype O:3 reduces expression of both O-antigen and outer core gene clusters of the LPS 21 , and putative ops sites were identified proximal to both O-antigen and outer core gene clusters in Y . enterocolitica .…”