A Caenorhabditis elegans model of Yersinia infection: biofilm formation on a biotic surface

Abstract

To investigate Yersinia pathogenicity and the evolutionary divergence of the genus, the effect of pathogenic yersiniae on the model organism Caenorhabditis elegans was studied. Three strains of Yersinia pestis, including a strain lacking pMT1, caused blockage and death of C. elegans; one strain, lacking the haemin storage (hms) locus, caused no effect. Similarly, 15 strains of Yersinia enterocolitica caused no effect. Strains of Yersinia pseudotuberculosis showed different levels of pathogenicity. The majority of strains (76 %) caused no discernible effect; 5 % caused a weak infection, 9?5 % an intermediate infection, and 9?5 % a severe infection. There was no consistent relationship between serotype and severity of infection; nor was there any relationship between strains causing infection of C. elegans and those able to form a biofilm on an abiotic surface. Electron microscope and cytochemical examination of infected worms indicated that the infection phenotype is a result of biofilm formation on the head of the worm. Seven transposon mutants of Y. pseudotuberculosis strain YPIII pIB1 were completely or partially attenuated; mutated genes included genes encoding proteins involved in haemin storage and lipopolysaccharide biosynthesis. A screen of 15 defined C. elegans mutants identified four where mutation caused (complete) resistance to infection by Y. pseudotuberculosis YPIII pIB1. These mutants, srf-2, srf-3, srf-5 and the dauer pathway gene daf-1, also exhibit altered binding of lectins to the nematode surface. This suggests that biofilm formation on a biotic surface is an interactive process involving both bacterial and invertebrate control mechanisms.

The importance of the Rcs phosphorelay in the survival and pathogenesis of the enteropathogenic yersiniae

“…However, biofilm formation was not completely abolished in the mutant strains. In contrast, using our C. elegans model of biofilm formation on a biotic surface (Joshua et al, 2003) only the YPIII pIB1 strain of Y. pseudotuberculosis was able to form a biofilm and no difference was observed between wild-type and the rcs mutants (data not shown).…”

“…The analysis of biofilms on a biotic surface was performed using the Caenorhabditis elegans model as previously described (Joshua et al, 2003). C. elegans were maintained on NGM agar with E. coli strain OP50 as a food source.…”

Yersinia pestis Biofilm in the Flea Vector and Its Role in the Transmission of Plague

“…Answers to these and other questions will provide important insight into the biology and evolution of the Yersinia. For example, strains of Y. pestis and Y. pseudotuberculosis that have identical hmsHFRS, hmsT, and hmsP genes differ in their biofilm phenotype in different in vitro conditions (Chain et al 2004;Darby et al 2002;Deng et al 2002;Joshua et al 2003;Parkhill et al 2001). Of greatest biological significance, Y. pseudotuberculosis can infect the flea midgut but never forms a biofilm in that environment (Erickson et al 2006).…”

“…Key evidence for the biofilm model of plague transmission came from in vivo studies using the rat flea X. cheopis as an infection model, in which the Y. pestis hms genes were shown to be required to produce a transmissible infection in the flea proventriculus (Hinnebusch et al 1996;Jarrett et al 2004). The first explicit statement of the plague biofilm transmission hypothesis, however, was based on the ability of Y. pestis and Y. pseudotuberculosis to form Hms-dependent biofilm on the surface of Caenorhabditis elegans nematodes, a model that may incorporate aspects of both in vitro and in vivo biofilm formation (Darby et al 2002;Joshua et al 2003). In this model, Yersinia biofilm aggregates on the mouthparts and blocks the feeding of the nematodes as they crawl across a preformed lawn of ECM-producing bacteria.…”

“…As in other bacteria, the Hms-dependent ECM is required for Congo red binding (pigmentation), the binding of other ligands with polysaccharide affinity such as calcofluor ) and certain lectins (Tan and Darby 2004), as well as for Yersinia biofilm formation (Darby et al 2002;Forman et al 2006;Jarrett et al 2004;Joshua et al 2003).…”