The DegU orphan response regulator of Listeria monocytogenes autorepresses its own synthesis and is required for bacterial motility, virulence and biofilm formation.
The Gram-positive intracellular pathogen Listeria monocytogenes is endowed with 17 sets of genes encoding two-component systems. L. monocytogenes is closely related to the Gram-positive model bacterium Bacillus subtilis, in which we have shown previously that the DegS/DegU system plays a central role in controlling stationary phase adaptive responses, including degradative enzyme synthesis and competence. Although an orthologue of the DegU response regulator is present in L. monocytogenes, the gene encoding the cognate DegS kinase is conspicuously absent. We have inactivated the degU gene of L. monocytogenes and shown that DegU negatively regulates its own synthesis. Direct binding of L. monocytogenes DegU to its own promoter region was shown in vitro by gel mobility shift and DNase I footprinting experiments. DegU was also shown to bind upstream from the motB operon, which also encodes the GmaR anti-repressor of flagellar synthesis. In contrast to the situation in B. subtilis, DegU was shown to be essential for flagellar synthesis and bacterial motility in L. monocytogenes and is cotranscribed with the yviA gene located downstream. We also show that DegU is required for growth at high temperatures, adherence to plastic surfaces and the formation of efficient biofilms by L. monocytogenes. DegU plays a role in virulence of L. monocytogenes as well: in a murine intravenous infection model, an 11-fold increase in LD(50) was observed for the degU mutant. Taken together, our results indicate that despite the lack of the DegS kinase, DegU is fully functional as an orphan response regulator, and plays a central role in controlling several crucial adaptive responses in L. monocytogenes.
Gueriri
Ibtissem
I
Unité de Biologie des Bactéries Pathogènes à Gram Positif, CNRS URA 2172, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France.
Cyncynatus
Camille
C
Unité de Biologie des Bactéries Pathogènes à Gram Positif, CNRS URA 2172, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France.
Dubrac
Sarah
S
Unité de Biologie des Bactéries Pathogènes à Gram Positif, CNRS URA 2172, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France.
Arana
Alejandro Toledo
AT
Laboratory of Bacterial Biofilms, Instituto De Agrobiotecnologia Y Recursos Naturales, Universidad Pública de Navarra, 31006 Pamplona, Spain.
Dussurget
Olivier
O
Unité des Interactions Bactéries Cellules, INSERM U604, INRA USC2020, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France.
Msadek
Tarek
T
Unité de Biologie des Bactéries Pathogènes à Gram Positif, CNRS URA 2172, Institut Pasteur, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France.
D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification; D018441:Biofilms / Q000254:growth & development*; D002633:Chemotaxis; D015536:Down-Regulation; D005407:Flagella / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D008089:Listeria monocytogenes / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D011401:Promoter Regions, Genetic; D014774:Virulence
D001426:Bacterial Proteins; C066497:DegU protein, Bacteria