The msaABCR Operon Regulates Persister Formation by Modulating Energy Metabolism in Staphylococcus aureus

Abstract

Staphylococcus aureus is a major human pathogen that causes chronic, systemic infections, and the recalcitrance of these infections is mainly due to the presence of persister cells, which are a bacterial subpopulation that exhibits extreme, yet transient, antibiotic tolerance accompanied by a transient halt in growth. However, upon cessation of antibiotic treatment, a resumption in growth of persister cells causes recurrence of infections and treatment failure. Previously, we reported the involvement of msaABCR in several important staphylococcal phenotypes, including the formation of persister cells. Additionally, observations of the regulation of several metabolic genes by the msaABCR operon in transcriptomics and proteomics analyses have suggested its role in the metabolic activities of S. aureus. Given the importance of metabolism in persister formation as our starting point, in this study we demonstrated how the msaABCR operon regulates energy metabolism and subsequent antibiotic tolerance. We showed that deletion of the msaABCR operon results in increased tricarboxylic acid (TCA) cycle activity, accompanied by increased cellular ATP content and higher NADH content in S. aureus cells. We also showed that msaABCR (through MsaB) represses the ccpE and ndh2 genes, thereby regulating TCA cycle activity and the generation of membrane potential, respectively. Together, the observations from this study led to the conclusion that msaABCR operon deletion induces a metabolically hyperactive state, leading to decreased persister formation in S. aureus.

A Functional Menadione Biosynthesis Pathway is Required for Capsule Production by Staphylococcus aureus

“…There are contradictory reports in the literature on the effect the switch to SCV has on capsule production [19-21], and as such we sought to resolve these contradictions by verifying our GWAS findings with a focus on the menD gene. The menD gene encodes an enzyme involved in the biosynthesis of menadione, which is a vitamin K2 precursor that is synthesised by S. aureus [15].…”

“…Mutations in this gene have been shown in many studies to be responsible for an alternative means utilized by S. aureus to both resist the effect of antibiotics and evade clearance by phagocytes by switching to the slow growing small colony variant (SCV) or persistor phenotype [15-17]. The expression of many virulence factors is reduced when the bacteria switch to SCVs, including the production of cytolytic toxins [18]; however, there are contradictory reports on what effect this switch has on capsule production [19-21]. In this study we explore the link between the SCV phenotype and capsule production and conclude that the link is dependent upon the specific pathway that becomes mutated during the switch to the SCV form.…”

A functional menadione biosynthesis pathway is required for capsule production by Staphylococcus aureus

“…There are contradictory reports in the literature on the effect the switch to SCV has on capsule production [19–21], and as such we sought to resolve these contradictions by verifying our GWAS findings with a focus on the menD gene. The menD gene encodes an enzyme involved in the biosynthesis of menadione, which is a vitamin K2 precursor that is synthesised by S.…”

“…aureus to both resist the effect of antibiotics and evade clearance by phagocytes by switching to the slow growing small colony variant (SCV) or persister phenotype [15–17]. The expression of many virulence factors is reduced when the bacteria switch to SCVs, including the production of cytolytic toxins [18]; however, there are contradictory reports on what effect this switch has on capsule production [19–21]. In this study we explore the link between the SCV phenotype and capsule production and conclude that the link is dependent upon the specific pathway that becomes mutated during the switch to the SCV form.…”

Comparative Transcriptomic Analysis of Staphylococcus aureus Reveals the Genes Involved in Survival at Low Temperature

“…Among the genes that encode proteins involved in energy metabolism, the NADH dehydrogenase gene ( nadE ) was upregulated 2.59 log2(FC) in BB-11 compared to BA-26; the malA gene encoding α-glucosidase was upregulated 3.34 log2(FC) in BB-11 but was downregulated −1.39 log2(FC) in BA-26. NADH dehydrogenase is the largest bacterial electron transport complex that transfers electrons directly to the respiratory chain through redox reactions and generates energy for use in cellular processes [ 41 ]. Moreso, α-Glucosidase is an exoenzyme widely found in bacteria, and its mode of action is similar to that of glucoamylase on disaccharides, oligosaccharides, and aryl glycosides and produces glucose [ 42 ].…”