Abstract
Carbon catabolite repression (CCR) is a common mechanism pathogenic bacteria use to link central metabolism with virulence factor synthesis. In gram-positive bacteria, catabolite control protein A (CcpA) and the histidine-containing phosphocarrier protein HPr (encoded by ptsH) are the predominant mediators of CCR. In addition to modulating CcpA activity, HPr is essential for glucose import via the phosphotransferase system. While the regulatory functions of CcpA in Staphylococcus aureus are largely known, little is known about the function of HPr in CCR and infectivity. To address this knowledge gap, ptsH mutants were created in S. aureus that either lack the open reading frame or harbor a ptsH variant carrying a thymidine to guanosine mutation at position 136, and the effects of these mutations on growth and metabolism were assessed. Inactivation of ptsH altered bacterial physiology and decreased the ability of S. aureus to form a biofilm and cause infections in mice. These data demonstrate that HPr affects central metabolism and virulence in S. aureus independent of its influence on CcpA regulation.
Highlights
To determine if inactivation of ptsH in S. aureus leads to changes in growth and carbon catabolism, mutants were constructed in the S. aureus laboratory strain Newman (Table 1)
A ptsH mutant harboring a point mutation in the ptsH gene (T136G) leading to the substitution of serine to alanine at position 46 of histidine-containing phosphocarrier protein (HPr) (HPr-S46A) was constructed. The phosphorylation at this amino acid represents a known prerequisite for HPr to activate catabolite control protein A (CcpA) in other gram-positive bacteria (14), while its activity in the phosphotransferase uptake system (PTS) should be unaffected
After 12 h of cultivation, growth yields were comparable for all strains (Figure 1b), suggesting that neither the lack of CcpA nor HPr has a clear long-term effect on biomass production of S. aureus cultured in rich medium
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Microorganisms 2021, 9, 466 on Ser-46 [7] This ATP-requiring process is catalyzed by the HPr-kinase/phosphorylase (HPrK/P), which is regulated in a dose-dependent manner by the glycolytic intermediate fructose-1,6-bisphosphate (FBP) [10]. For this reason, the amount of Ser-46 phosphorylated. CcpA promotes transcription of the icaoperon and cidA [19], encoding proteins needed for polysaccharide intercellular adhesion (PIA) synthesis and extracellular DNA release, respectively [22,23] These observations are consistent with the fact that deletion of ccpA abrogates biofilm formation under glucoserich conditions. We characterize the function of HPr of S. aureus in the context of carbon metabolism, growth kinetics, biofilm formation, and in vivo infectivity in different murine infection models
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