Regulation of Metalloprotease Gene Expression in Vibrio vulnificus by a Vibrio harveyi LuxR Homologue

Abstract

Expression of the Vibrio vulnificus metalloprotease gene, vvp, was turned up rapidly when bacterial growth reached the late log phase. A similar pattern of expression has been found in the metalloprotease gene of Vibrio cholerae, and this has been shown to be regulated by a Vibrio harveyi LuxR-like transcriptional activator. To find out whether a LuxR homologue exists in V. vulnificus, a gene library of this organism was screened by colony hybridization using a probe derived from a sequence that is conserved in various luxR-like genes of vibrios. A gene containing a 618-bp open reading frame was identified and found to be identical to the smcR gene of V. vulnificus reported previously. An isogenic SmcR-deficient (RD) mutant was further constructed by an in vivo allelic exchange technique. This mutant exhibited an extremely low level of vvp transcription compared with that of the parent strain. On the other hand, the cytolysin gene, vvhA, was expressed at a higher level in the RD mutant than in the parent strain during the log phase of growth. These data suggested that SmcR might not only be a positive regulator of the protease gene but might also be involved in negative regulation of the cytolysin gene. Virulence of the RD mutant in either normal or iron-overloaded mice challenged by intraperitoneal injection was comparable to that of the parent strain, indicating that SmcR is not required for V. vulnificus virulence in mice.

Vibrio vulnificus Vulnibactin, But Not Metalloprotease VvpE, Is Essentially Required for Iron-Uptake from Human Holotransferrin

“…Without exception, reports issued to date demonstrate that VvpE expression occurs during the late exponential or stationary growth phase. [34][35][36][37] These results evidently indicate that VvpE is not involved in facilitating vulnibactin-mediated iron-assimilation via the proteolytic cleavage of transferrins. DF-HI broth containing HT as an iron source and human body fluids present an iron-limited condition because transferrin-bound iron is not freely available for V. vulnificus.…”

SmcR and Cyclic AMP Receptor Protein Coactivate Vibrio vulnificus vvpE Encoding Elastase through the RpoS-dependent Promoter in a Synergistic Manner

“…, it has been suggested that SmcR positively regulates vvpE gene expression in V. vulnificus (10). Thus, to further examine the regulation of vvpE by SmcR, V. vulnificus smcR mutants were constructed by allelic exchange (Fig.…”

“…Compared with the substantial number of reports on the characterization of purified elastase, there have been only a few studies on the regulatory mechanism used by the bacterium to modulate the expression of the vvpE gene (9,10). In a previous report, we showed that transcription of the vvpE gene of V. vulnificus is initiated by two different types of promoter, promoter L (PL) 1 and promoter S (PS), in a growth phase-dependent manner (9).…”

“…This differential utilization of two promoters can permit precise levels of elastase in response to modifications of the environment and growth stage. Meanwhile, it has been reported that SmcR, the Vibrio harveyi LuxR homolog, is also involved in the positive control of vvpE expression (10).…”

Role of Alkaline Serine Protease, Asp, in Vibrio alginolyticus Virulence and Regulation of Its Expression by LuxO-LuxR Regulatory System

“…could use this system to control many processes including bioluminescence, virulence, mobility, biofilm formation, and extracellular polysaccharide production [32]. Significantly, extracellular proteases, the virulence factors of Vibrio spp., were shown to be regulated by their respective quorum sensing systems, such as hemagglutinin protease hap in V. cholerae [13], metalloprotease empA in V. anguillarum [6], and metalloprotease vvp and cytolysin vvhA in V. vulnificus [25].Vibrio alginolyticus, a ubiquitous organism in seawater, has been isolated from different organisms as part of the normal marine flora. However, it has also been suggested that this species was a pathogen of several marine animals and humans.…”