msaABCR Operon Regulates Staphylococcal Metabolism to Promote Virulence Expression and Biofilm Formation
Bibek G C, Gyan S. Sahukhal, Mohamed O. Elasri
Department of Biological Sciences, The University of Southern Mississippi, Hattiesburg, MS
Key problem with Staphylococcus aureus as a pathogen is the acquisition of antibiotic resistance and their ability to produce biofilm formation. They are also equipped with robust mechanism against several host responses including oxidative stresses. Bacteria can take up and utilize sugars and amino sugars in the cytoplasm for ATP production through glycolysis and the synthesis of bacterial components (e.g., peptidoglycan, lipoteichoic acid, WTA) and virulence factors (capsule, carotenoid pigment, toxins). Thus, allocation of sugar into different pathways is critical for virulence regulation and survival of bacteria. Our studies show that msaABCR regulates tightly regulated programmed cell death (PCD) phenomenon via cidABC pathway during biofilm development in USA300 LAC strain. msaABCR mutant consumed glucose and produced acetate at a higher rate compared to wild type in biofilm microenvironment leading to increased cell death. We also measured glucose consumption and acetate production rate during exponential growth phase, and acetate reutilization rate at stationary growth phase in msaABCR mutant cells. Results shows that msaABCR consumes glucose, generate acetate and reutilize acetate at faster rate compared to wild type. Aconitase activity measurement in msaABCR mutant showed increased TCA activity in mutant cells in stationary growth phase. Furthermore, msaABCR mutant’s growth yield and acetate generation significantly increased when grown in TSB plus 1% pyruvate compared to wild type. Expression of msaABCR operon was increased when grown in TSB with 1% pyruvate compared to TSB only. Thus, increased oxidative energy metabolism (increased acetate production, acetate reutilization, TCA activity), decreased cell wall thickness, teichoic acid content, capsule and carotenoid production in msaABCR-mutant cells suggests that msaABCR operon regulates staphylococcal metabolism to promote cell envelope synthesis, virulence factor synthesis and biofilm formation. Furthermore, msaABCR operon is induced by pyruvate which is central metabolites of staphylococcal metabolism.