Search

PhoU proteins are negative regulators of the phosphate response, regulate virulence, and contribute to antibiotic resistance. Staphylococcus aureus has multiple genes encoding PhoU homologs that regulate persister formation and potentially virulence, but the molecular mechanisms of this regulation are not fully understood. We used a bacterial adenylate cyclase two-hybrid system to assess interactions between PhoU homologs and other proteins known to interact with PhoU from Escherichia coli. S. aureus PhoU (also referred to as PhoU1) interacted with PhoU itself; PitR (also referred to as PhoU2) interacted with PitR itself. We identified potential structural and dimerization models for S. aureus PhoU homologs. Dimerization was confirmed using size exclusion chromatography of purified proteins. These results highlight the complex nature of PhoU proteins. Further analysis may elucidate the potential mechanisms for regulating gene expression, persister formation, and virulence in S. aureus .IMPORTANCEPhoU proteins affect pathogenesis and persister formation in many bacterial species. This protein is essential for signaling environmental phosphate levels in Escherichia coli but is still not well characterized in many other pathogenic bacterial strains. This work identifies some similarities and key differences in Staphylococcus aureus PhoU homologs compared to E. coli PhoU, specifically, PhoU and PitR from S. aureus form homodimers but do not appear to interact with PhoR or phosphate transporter proteins.

Staphylococcus aureus is a major human pathogen whose infections are increasingly difficult to treat due to increased antibiotic resistance, including resistance to vancomycin. Vancomycin-intermediate S. aureus (VISA) strains develop resistance to vancomycin through adaptive changes that are incompletely understood. Central to this adaptation are metabolic changes that permit growth in the presence of vancomycin. To define the metabolic changes associated with adaptive resistance to vancomycin in S. aureus , the metabolomes of a vancomycin-sensitive and VISA strain pair isolated from the same patient shortly after vancomycin therapy began and following vancomycin treatment failure were analyzed. The metabolic adaptations included increases in acetogenesis, carbon flow through the pentose phosphate pathway, wall teichoic acid and peptidoglycan precursor biosynthesis, purine biosynthesis, and decreased tricarboxylic acid (TCA) cycle activity. The significance of these metabolic pathways for vancomycin-intermediate susceptibility was determined by assessing the synergistic potential of human-use-approved inhibitors of these pathways in combination with vancomycin against VISA strains. Importantly, inhibitors of amino sugar and purine biosynthesis acted synergistically with vancomycin to kill a diverse set of VISA strains, suggesting that combinatorial therapy could augment the efficacy of vancomycin even in patients infected with VISA strains., (Copyright © 2017 American Society for Microbiology.)