Anaerobic gene expression in Staphylococcus aureus

Institut für Mikrobiologie, Jahnstrasse 15, 17487 Greifswald, Germany

^* To whom correspondence should be addressed. Email: Susanne.Engelmann{at}uni-greifswald.de.

	Abstract

An investigation of gene expression in S. aureus after a switch from aerobic to anaerobic growth was initiated by using the proteomic and transcriptomic approach. In the absence of external electron acceptors like oxygen or nitrate an induction of glycolytic enzymes was observed. At the same time the amount of TCA cycle enzymes was very low. NAD is regenerated by mixed acid and butanediol fermentation indicated by an elevated synthesis level of fermentation enzymes like lactate dehydrogenases (Ldh1, Ldh2), alcohol dehydrogenases (AdhE, Adh), -acetolactate decarboxylase (BudA1), acetolactate synthase (BudB), and acetoin reductase (SACOL0111) as well as an accumulation of fermentation products as lactate and acetate. Moreover, the transcription of genes possibly involved in secretion of lactate (SACOL2363) and formate (SACOL0301) was found to be induced. The formation of acetyl-CoA/acetyl-phosphate might be catalyzed by pyruvate formate lyase whose synthesis was found to be strongly induced as well. Although nitrate was not present, the expression of genes related to nitrate respiration (NarH, NarI, NarJ) and nitrate reduction (NirD) was found to be up-regulated. Of particular interest, oxygen concentration might affect virulence properties of S. aureus by regulating the expression of some virulence associated genes such as pls, hlY, splC and splD, epiG, and isaB. To date the mechanism of anaerobic gene expression in S. aureus has not been fully characterized. Besides srrA the mRNA level of several other regulatory genes with so far unknown function (e. g. SACOL0201, SACOL2360, and SACOL2658) was found to be upregulated during anaerobic growth indicating a role in the regulation of anaerobic gene expression.