title: Characterization of the oxygen-responsive NreABC regulon of Staphylococcus aureus.
abstract: Here, we investigate the functionality of the oxygen-responsive nitrogen regulation system NreABC in the human pathogen Staphylococcus aureus and evaluate its role in anaerobic gene regulation and virulence factor expression. Deletion of nreABC resulted in severe impairment of dissimilatory nitrate and nitrite reduction and led to a small-colony phenotype in the presence of nitrate during anaerobic growth. For characterization of the NreABC regulon, comparative DNA microarray and proteomic analyses between the wild type and nreABC mutant were performed under anoxic conditions in the absence and presence of nitrate. A reduced expression of virulence factors was not observed in the mutant. However, both the transcription of genes involved in nitrate and nitrite reduction and the accumulation of corresponding proteins were highly decreased in the nreABC mutant, which was unable to utilize nitrate as a respiratory oxidant and, hence, was forced to use fermentative pathways. These data were corroborated by the quantification of the extracellular metabolites lactate and acetate. Using an Escherichia coli-compatible two-plasmid system, the activation of the promoters of the nitrate and nitrite reductase operons and of the putative nitrate/nitrite transporter gene narK by NreBC was confirmed. Overall, our data indicate that NreABC is very likely a specific regulation system that is essential for the transcriptional activation of genes involved in dissimilatory reduction and transport of nitrate and nitrite. The study underscores the importance of NreABC as a fitness factor for S. aureus in anoxic environments.
authors.affiliation: Microbial Genetics, University of Tübingen, 72076 Tübingen, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Schlag
authors.forename: Stephan
authors.initials: S
authors.lastname: Fuchs
authors.forename: Christiane
authors.initials: C
authors.lastname: Nerz
authors.forename: Rosmarie
authors.initials: R
authors.lastname: Gaupp
authors.forename: Susanne
authors.initials: S
authors.lastname: Engelmann
authors.forename: Manuel
authors.initials: M
authors.lastname: Liebeke
authors.forename: Michael
authors.initials: M
authors.lastname: Lalk
authors.forename: Michael
authors.initials: M
authors.lastname: Hecker
authors.forename: Friedrich
authors.initials: F
authors.lastname: Götz
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001482:Base Composition; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000502:physiology; D005816:Genetic Complementation Test; D009566:Nitrates / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D018085:Regulon / Q000502:physiology*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D009566:Nitrates; D051922:PII Nitrogen Regulatory Proteins; D010100:Oxygen