Comparative analysis of biofilm formation by main and nonmain subspeciesYersinia pestisstrains

Abstract

The biofilm-forming phenotype of 14 isolates from four 'nonmain' subspecies of Yersinia pestis was compared with eight isolates from the more commonly studied 'main' or epidemic subspecies of Y. pestis in this study. The four nonmain subspecies are more geographically limited, and are associated with certain mammalian hosts and regions of the Caucasus and Central Asia, whereas the main subspecies spread worldwide during the historic plague pandemics. With the main subspecies pestis, pigmentation on Congo red medium (CR(+)) correlated with biofilm formation on both abiotic and biotic surfaces. Main subspecies pestis strains that do not produce pigmentation on Congo red medium (CR(-)) have a deletion that includes the hmsF and hmsS genes known to be required for biofilm formation. CR(-) strains of the nonmain subspecies, altaica and ulegeica, differed however from pestis and, while defective for biofilms on the two surfaces, both had intact hmsF and hmsS genes. The presence of rcsA was also investigated and results showed that it occurred with a 30-bp insertion in all forms of the subspecies. These findings suggest that biofilms are regulated differently in altaica and ulegeica than they are in pestis and also indicate that the rcsA pseudogene arose early in Y. pestis evolution, increasing the ability of the strain to form biofilm and thereby increasing its effective transmission.

Antivirulence Genes: Insights into Pathogen Evolution through Gene Loss

“…pestis, but is also suspected to be prevalent in all other subspecies (Y. pestis subsp. caucasica, altaica, hissarica, and ulegeica) (15). This result suggests that inactivation of rcsA likely occurred early in Y. pestis evolution, possibly as a result of considerable selective pressure upon the bacteria to inactivate rcsA and allow for biofilm formation in order to enhance transmission from the flea.…”

Systematic analysis of cyclic di‐GMP signalling enzymes and their role in biofilm formation and virulence in Yersinia pestis

“…The ability of Y. pestis to form biofilms in fleas correlates with Hms‐dependent EPS production, which causes absorption of CR dye from the growth medium at temperatures below 34°C. Y. pseudotuberculosis also possesses the hms genes, but most strains form non‐pigmented colonies on CR agar at ambient temperatures and do not form biofilms in fleas (Brubaker, 1991; Hinnebusch et al ., 1996; Jones et al ., 1999; Erickson et al ., 2006; Eroshenko et al ., 2010). During the evolution from Y. pseudotuberculosis , Y. pestis lost motility and acquired the ability to form biofilms in fleas, likely the result of several mutations.…”

The Yersinia pestis HmsCDE regulatory system is essential for blockage of the oriental rat flea (Xenopsylla cheopis), a classic plague vector

“…Pestoides strains are reported to be avirulent for humans and are thought to be intermediates between the Y. pestis ancestor, Y. pseudotuberculosis, and epidemic Y. pestis strains (Anisimov et al, 2004;Cui et al, 2008;Bearden et al, 2009; Bobrov et al, 2011). In addition, there is evidence in the literature of different degrees of biofilm-dependent blockage in a Caenorhabditis elegans model and some flea species by epidemic and endemic Y. pestis strains (Vatschenok, 1988;Anisimov, 2002;Eroshenko et al, 2010). To address whether the HmsCDE system may play a role in biofilm regulation in Y. pestis strains other than KIM6+, we examined strains from our collection that represent all the main phylogenetic branches of Y. pestisthe three epidemic biovars and two clades of endemic strains.…”