The bile salt sodium taurocholate inducesCampylobacter jejuniouter membrane vesicle production and increases OMV-associated proteolytic activity

Abstract

Campylobacter jejuni, the leading cause of bacterial acute gastroenteritis worldwide, secretes an arsenal of virulence-associated proteins within outer membrane vesicles (OMVs). C. jejuni OMVs contain three serine proteases (HtrA, Cj0511, and Cj1365c) that cleave the intestinal epithelial cell (IEC) tight and adherens junction proteins occludin and E-cadherin, promoting enhanced C. jejuni adhesion to and invasion of IECs. C. jejuni OMVs also induce IECs innate immune responses. The bile salt sodium taurocholate (ST) is sensed as a host signal to coordinate the activation of virulence-associated genes in the enteric pathogen Vibrio cholerae. In this study, the effect of ST on C. jejuni OMVs was investigated. Physiological concentrations of ST do not have an inhibitory effect on C. jejuni growth until the early stationary phase. Coculture of C. jejuni with 0.1% or 0.2% (w/v) ST stimulates OMV production, increasing both lipid and protein concentrations. C. jejuni ST-OMVs possess increased proteolytic activity and exhibit a different protein profile compared to OMVs isolated in the absence of ST. ST-OMVs exhibit enhanced cytotoxicity and immunogenicity to T84 IECs and enhanced killing of Galleria mellonella larvae. ST increases the level of mRNA transcripts of the OMVs-associated serine protease genes and the cdtABC operon that encodes the cytolethal distending toxin. Coculture with ST significantly enhances the OMVs-induced cleavage of E-cadherin and occludin. C. jejuni OMVs also cleave the major endoplasmic reticulum chaperone protein BiP/GRP78 and this activity is associated with the Cj1365c protease. These data suggest that C. jejuni responds to the presence of physiological concentrations of the bile salt ST that increases OMV production and the synthesis of virulence-associated factors that are secreted within the OMVs. We propose that these events contribute to pathogenesis.

Campylobacter jejuni bile exposure influences outer membrane vesicles protein content and bacterial interaction with epithelial cells

“…Our data are to some extent different from those recently reported by Elmi and co-workers 45 studying the effects of taurocholate on C . jejuni OMVs.…”

“…Bile did however not affect CDT abundance in the bacteria. None of the Campylobacter invasion antigens (Cia) were detected in OMVs in our setting, and neither was CiaB detected in OMVs after growth in taurocholate 45 . This is in line with that the flagellum is known to be the secretion apparatus for Cia proteins 20 and CiaB protein was detected in bacteria only but with no alteration in the protein level by low bile at 20 h. Increased transcription and translation of ciaB gene in bacteria was previously shown with high concentration of bile 46 , 47 .…”

“…jejuni 11168 55 , and also the pTet and pVir plasmids, which are not present in 11168 55 – 58 . Elmi and co-workers suggested higher abundance of three serine proteases in response to taurocholate 45 . Of these, only HtrA and CtpA (corresponding to Cj0511 in strain 11168) were detected but not altered by bile in OMV-B and WT-B.…”

Biofilm formation and extracellular microvesicles—The way of foodborne pathogens toward resistance

“…According to Taheri et al [176] composition of the C. jejuni MVs depends on growth temperature and it has implications for the outcome of colonization and pathogenicity of this bacterium in different hosts. Elmi et al [185] indirectly confirmed the abovementioned findings by Taheri et al [184] using bile salt sodium taurocholate. After treatment with this bile salt, C. jejuni outer MV production increased, with increased MVs-associated proteolytic activity as a consequence.…”

Function of serine protease HtrA in the lifecycle of the foodborne pathogen Campylobacter jejuni

“…A more detailed experimental analysis revealed that the Cj0511 serine peptidase, which was shown to be present in C. jejuni OMVs in conjunction with the HtrA and Cj1365c proteases [ 94 ], is essential for chicken colonization. The findings that OMVs produced in the presence of the bile salt taurocholic acid exerted elevated proteolytic activity and were found to be required for C. jejuni invasion and transmigration in vitro underlined the functions of the secreted proteases in C. jejuni virulence and intestinal pathogenesis [ 120 ]. Taken together, all these findings provided the first evidence that the other proteases of C. jejuni might represent excellent targets for antibacterial therapy and the protection of lifestock from C. jejuni colonization.…”