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Infect Immun. 2019 Jan 24;87(2). pii: e00570-18. doi: 10.1128/IAI.00570-18. Print 2019 Feb.

Interplay of Nitric Oxide Synthase (NOS) and SrrAB in Modulation of Staphylococcus aureus Metabolism and Virulence.

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Department of Microbiology and Cell Science, IFAS, University of Florida, Gainesville, Florida, USA.
Department of Microbiology, Molecular Genetics and Immunology, The University of Kansas Medical Center, Kansas City, Kansas, USA.
Department of Microbiology and Cell Science, IFAS, University of Florida, Gainesville, Florida, USA


Staphylococcus aureus nitric oxide synthase (saNOS) is a major contributor to virulence, stress resistance, and physiology, yet the specific mechanism(s) by which saNOS intersects with other known regulatory circuits is largely unknown. The SrrAB two-component system, which modulates gene expression in response to the reduced state of respiratory menaquinones, is a positive regulator of nos expression. Several SrrAB-regulated genes were also previously shown to be induced in an aerobically respiring nos mutant, suggesting a potential interplay between saNOS and SrrAB. Therefore, a combination of genetic, molecular, and physiological approaches was employed to characterize a nos srrAB mutant, which had significant reductions in the maximum specific growth rate and oxygen consumption when cultured under conditions promoting aerobic respiration. The nos srrAB mutant secreted elevated lactate levels, correlating with the increased transcription of lactate dehydrogenases. Expression of nitrate and nitrite reductase genes was also significantly enhanced in the nos srrAB double mutant, and its aerobic growth defect could be partially rescued with supplementation with nitrate, nitrite, or ammonia. Furthermore, elevated ornithine and citrulline levels and highly upregulated expression of arginine deiminase genes were observed in the double mutant. These data suggest that a dual deficiency in saNOS and SrrAB limits S. aureus to fermentative metabolism, with a reliance on nitrate assimilation and the urea cycle to help fuel energy production. The nos, srrAB, and nos srrAB mutants showed comparable defects in endothelial intracellular survival, whereas the srrAB and nos srrAB mutants were highly attenuated during murine sepsis, suggesting that SrrAB-mediated metabolic versatility is dominant in vivo.


SrrAB; Staphylococcus aureus ; bacterial nitric oxide synthase; cell respiration; metabolomics; sepsis; two-component system

[Available on 2019-07-24]

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