The Yersinia genus comprises pathogens that are able to adapt to an environmental life cycle stage as well as to mammals. Yersinia enterocolitica strain W22703 exhibits both insecticidal and nematocidal activity conferred by the tripartite toxin complex (Tc) that is encoded on the 19 kb pathogenicity island Tc-PAIYe. All tc genes follow a strict temperature regulation in that they are silenced at 37°C, but activated at lower temperatures. Four highly-conserved phage-related genes, located within the Tc-PAIYe, were recently demonstrated to encode a biologically functional holin-endolysin gene cassette that lyses its own host W22703 at 37°C (1). Conditions transcriptionally activating the cassette are yet unknown. In contrast to E. coli, the overproduction of holin and endolysin did not result in cell lysis of strain W22703 15°C. When the holin-endolysin genes were overexpressed at 15°C in four Y. enterocolitica biovars and in four other Yersinia spp., a heterogenous pattern of phenotypes was observed, ranging from lysis resistance of a biovar 1A strain to a complete growth arrest of a Y. kristensenii strain. To decipher the molecular mechanism underlying this temperature-dependent lysis, we constructed a Lon protease negative mutant of W22703 in which overexpression of the lysis cassette leads to cell death at 15°C. Overexpressed endolysin exhibited a high proteolytic susceptibility in strain W22703, but remained stable in strain W22703 Δlon or in Y. pseudotuberculosis. Although artificial overexpression was applied here, the data indicate that Lon protease plays a role in the control of the temperature-dependent lysis in Y. enterocolitica W22703.
IMPORTANCE The investigation of the mechanisms that help pathogens to survive in the environment is a prerequisite to understand their evolution and their virulence capacities. In members of the genus Yersinia, many factors involved in virulence, metabolism, motility or biofilm formation follow a strict temperature-dependent regulation. While the molecular mechanisms underlying activation of determinants at body temperature have been analysed in detail, the molecular basis of low temperature-dependent phenotypes is largely unknown. Here, we demonstrate that a novel phage-related lysis cassette, which is part of the insecticidal and nematocidal pathogenicity island of Y. enterocolitica, does not lyse its own host following overexpression at 15°C, and that the Lon protease is involved in this phenotype.
Temperature‐dependent Influence of RpoF Overexpression on the
E. coli
Extracellular Proteome
