A chromosomally encoded type III secretion pathway in Yersinia enterocolitica is important in virulence

Abstract

SummaryNumerous Gram-negative bacteria use a type III, or contact dependent, secretion system to deliver proteins into the cytosol of host cells. All of these systems identified to date have been shown to have a role in pathogenesis. We have identified 13 genes on the Yersinia enterocolitica chromosome that encode a type III secretion apparatus plus two associated putative regulatory genes. In order to determine the function of this chromosomally-encoded secretion apparatus, we created an in frame deletion of a gene that has homology to the hypothesized inner membrane pore, ysaV. The ysaV mutant strain failed to secrete eight proteins, called Ysps, normally secreted by the parental strain when grown at 288C in Luria± Bertani (LB) broth supplemented with 0.4 M NaCl. Disruption of the ysaV gene had no effect on motility or phospholipase activity, suggesting this chromosomally encoded type III secretion pathway is distinct from the flagella secretion pathway of Y. enterocolitica. Deletion of the ysaV gene in a virulence plasmid positive strain had no effect on in vitro secretion of Yops by the plasmid-encoded type III secretion apparatus. Secretion of the Ysps was unaffected by the presence or absence of the virulence plasmid, suggesting the chromosomally encoded and plasmid-encoded type III secretion pathways act independently. Y. enterocolitica thus has three type III secretion pathways that appear to act independently. The ysaV mutant strain was somewhat attenuated in virulence compared with the wild type in the mouse oral model of infection (an approximately 0.9 log difference in LD 50 ). The ysaV mutant strain was nearly as virulent as the wild type when inoculated intraperitoneally in the mouse model. A ysaV probe hybridized to sequences in other Yersinia spp. and homologues were found in the incomplete Y. pestis genome sequence, indicating a possible role for this system throughout the genus.

Genome sequence of Yersinia pestis, the causative agent of plague

“…2). This secretion system is distinct from the chromosomally borne type III system in Y. enterocolitica 16 . We were unable to identify the effectors for this system, as these are generally divergent.…”

Evolutionary Dynamics of the Yersinia enterocolitica Complex

“…It has been suggested that YPM+ HPI-strains cause Far East scarlet fever, whereas YPM-HPI+ strains are linked with enteric disease (Fukushima, et al, 2001;Ch'ng, et al, 2011;Eppinger, et al, 2007). other Yersinia species and that is thought to be involved in virulence (Haller, Carlson, Pederson and Pierson, 2000;Foultier, et al, 2002). At least eight Yersinia secreted proteins, Ysps, depend on secretion by the Ysa T3SS (Haller, Carlson, Pederson and Pierson, 2000).…”

“…other Yersinia species and that is thought to be involved in virulence (Haller, Carlson, Pederson and Pierson, 2000;Foultier, et al, 2002). At least eight Yersinia secreted proteins, Ysps, depend on secretion by the Ysa T3SS (Haller, Carlson, Pederson and Pierson, 2000). It was shown that secretion by this system is activated at 28°C and high salt conditions, and that this secretion is independent from the plasmid-encoded…”

Untitled

“…It as a functional substitute of YopD [8,9,10,11]. Ysa-Ysp T3SS in general and syc-ysp operon in particular has been comparatively much less explored though it contains some very important chaperone like SycB, and unique translocator like YspC.…”

“…So, these proteins while forming the translocon are exposed to the extracellular milieu. Hence, they are potential therapeutic targets against the infection of Yersinia entercolitica, caused by the activation of Ysa-Ysp T3SS [7,8,9,10,11,12]. Our previous study showed that SycB interacts with YspC and forms a 1:1 heterodimeric complex [17,18].…”