Characterization of DegU, a response regulator inListeria monocytogenes, involved in regulation of motility and contributes to virulence

Abstract

The degU (lmo2515) gene encodes a putative response regulator in the food-borne pathogen Listeria monocytogenes. It has 63% amino acid identity to the DegU response regulator of Bacillus subtilis. We have characterized the degU gene product in L. monocytogenes EGD by generation of a deletion mutant. The DeltadegU mutant was found to be non-motile in motility plate assay and no flagellin was detected. The mutant was attenuated in challenge of mice. Northern blot analysis suggested that the degU gene product is a transcriptional activator of the flagellin gene, flaA, at 25 degrees C. However, the degU gene product had no influence on the transcription of prfA encoding the major virulence regulator, PrfA. The results indicate that the putative DegU response regulator is a pleiotropic regulator involved in expression of both motility at low temperature and in vivo virulence in mice.

A pivotal role for the response regulator DegU in controlling multicellular behaviour

“…DegU mutant strains are still able to enter host cells with an efficiency that is comparable to, or even better than, that of wild-type cells (Williams et al, 2005a). However, the bacterial load maintained within the spleen and other organs of the host is lower (Knudsen et al, 2004). DegU-dependent control of virulence is not due to the non-motile phenotype because flagella-minus strains of L. monocytogenes remain virulent .…”

“…The genome sequences of the pathogenic strain L. monocytogenes EGD-e and nonpathogenic strain L. innocua are remarkably similar to that of B. subtilis (Glaser et al, 2001). However, in the region surrounding degU, the degS homologue is conspicuously absent despite other major genome features being maintained (Gueriri et al, 2008b;Knudsen et al, 2004). The absence of degS appears to be specific to the Listeria species (Fig.…”

“…Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that causes listeriosis. DegU (encoded by lmo2515) regulates motility, biofilm formation and virulence in Listeria species (Gueriri et al, 2008b;Knudsen et al, 2004;Williams et al, 2005a, b). The genome sequences of the pathogenic strain L. monocytogenes EGD-e and nonpathogenic strain L. innocua are remarkably similar to that of B. subtilis (Glaser et al, 2001).…”

“…DegU was recently identified as a positive activator of flagellum biosynthesis (Knudsen et al, 2004;Williams et al, 2005a, b). When grown at ¡30 u C L. monocytogenes has four to six simple peritrichous glycosylated flagella.…”

Thermosensing to Adjust Bacterial Virulence in a Fluctuating Environment

“…Hence, the actual thermosensor in this process is not the DNA-binding protein MogR, but the interacting protein GmaR [155]. The response regulator DegU has also shown to be involved in the thermo-induced regulation of the flagellar motility genes [156,157].…”