Golden Pigment Production and Virulence Gene Expression Are Affected by Metabolisms in Staphylococcus aureus

Abstract

The pathogenesis of staphylococcal infections is multifactorial. Golden pigment is an eponymous feature of the human pathogen Staphylococcus aureus that shields the microbe from oxidation-based clearance, an innate host immune response to infection. Here, we screened a collection of S. aureus transposon mutants for pigment production variants. A total of 15 previously unidentified genes were discovered. Notably, disrupting metabolic pathways such as the tricarboxylic acid cycle, purine biosynthesis, and oxidative phosphorylation yields mutants with enhanced pigmentation. The dramatic effect on pigment production seems to correlate with altered expression of virulence determinants. Microarray analysis further indicates that purine biosynthesis impacts the expression of ϳ400 genes involved in a broad spectrum of functions including virulence. The purine biosynthesis mutant and oxidative phosphorylation mutant strains exhibit significantly attenuated virulence in a murine abscess model of infection. Inhibition of purine biosynthesis with a known smallmolecule inhibitor results in altered virulence gene expression and virulence attenuation during infection. Taken together, these results suggest an intimate link between metabolic processes and virulence gene expression in S. aureus. This study also establishes the importance of purine biosynthesis and oxidative phosphorylation for in vivo survival.Staphylococcus aureus causes a variety of infections in humans, ranging from minor skin and wound infections to lifethreatening diseases (31). The pathogenesis of staphylococcal infections is a multifactorial process that depends on the expression of different virulence factors controlled by multiple regulatory systems in conjunction with environmental and nutritional signals (46). The high degree of variability in the expression of virulence genes is modulated by a complex network regulated by factors such as the agr locus (RNAIII), SarA, and SigB (5, 9), which allows the bacterium to adapt to changing environmental conditions for survival and developing infection.The species epithet of S. aureus reflects its characteristic surface pigmentation (aureus, meaning "golden" in Latin) (43). The yellowish-orange (golden) pigment produced by S. aureus has been linked to virulence, owing to its antioxidant property (29,30). The golden pigmentation of S. aureus is the product of a C 30 triterpenoid carotenoid biosynthesis pathway, and the carotenoid pigment biosynthesis genes are organized in an operon crtOPQMN controlled by the alternative sigma factor SigB (3, 39). Since many virulence genes are coordinately regulated in S. aureus (5, 9, 31), we hypothesized that genes affecting pigmentation may also influence the production of virulence determinants and have an impact on the pathogenesis of S. aureus.Herein, we present an analysis of S. aureus golden pigment biosynthesis and regulatory pathways at the genomic level by screening the Phoenix (⌽N⌶) library, a collection of defined transposon insertions into 1,812 open reading frame...

Metabolic sensor governing bacterial virulence in Staphylococcus aureus

“…In S. aureus, TCA-cycle activity also was found to be critical for the elaboration of the capsule (55) and staphyloxanthin (24). In addition, down-regulation of the TCA cycle through aconitase (CitB) inactivation prevents the maximal expression of the virulence factors and therefore alters the interaction between S. aureus and the host (56).…”

“…Previously, we showed that the transposon insertion in the ccpE gene (SAV0672 in S. aureus Mu50) of the S. aureus Newman strain enhances the production of staphyloxanthin (24), a virulence factor used to evade host oxidative killing (25)(26)(27). To verify further that the effect of the ccpE transposon insertion was specific to ccpE disruption and was not an artifact of transposition, we generated a ccpE-deletion mutant in the S. aureus Newman strain as described in SI Appendix, Experimental Procedures.…”

“…To test further the role of ccpE in invasive staphylococcal disease, we subjected the test strains-wild type, ΔccpE, and ΔccpE-C-to a murine model of abscess formation (24,39) and measured the bacterial survival in host organs. As shown in Fig.…”

Outcome and Prevention of Pseudomonas aeruginosa-Staphylococcus aureus Interactions During Pulmonary Infections in Cystic Fibrosis

“…Also, a blocker of the synthesis of staphyloxanthin, the golden-carotenoid pigment of S. aureus that promotes resistance to reactive oxygen species and host neutrophil-based killing, increased the susceptibility of S. aureus to killing by human blood and the innate immune clearance in a mouse infection model (Liu et al, 2008). Other researchers have attempted to achieve virulence attenuation by manipulation of bacterial metabolism (Lan et al, 2010;Zhu et al, 2009). Another possible approach is to target the bacterial pathways for programmed cell death which have been identified in several species (Engelberg-Kulka et al, 2004).…”

Pigments and Pathogenesis

“…The gram positive pathogen Staphylococcus aureus is named such because it constitutively produces a golden yellow pigment [3]. When genes encoding synthetic enzymes responsible for the production of staphyloxanthin are deleted, the bacterium appears colourless.…”