Role of Lipase from Community-Associated Methicillin-Resistant Staphylococcus aureus Strain USA300 in Hydrolyzing Triglycerides into Growth-Inhibitory Free Fatty Acids

Cadieux, Brigitte; Vijayakumaran, Vithooshan; Bernards, Mark A.; McGavin, Martin J.; Heinrichs, David E.

doi:10.1128/jb.02044-14

Cited by 76 publications

(106 citation statements)

References 67 publications

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“…In MN8 ⌬sarA, as expected (42,43), we noted a prominent increase in expression of the aureolysin (Aur) metalloprotease and staphopain A (ScpA) cysteine protease. Aur is responsible for maturation of pro-Geh to mature Geh (44), which explains the near complete lack of pro-Geh in the sarA mutant. Thus, although the regulatory role of SarA and Sae for these other important exoproteins was largely predicted, a dominant role for regulation by Sae is selective for particular exotoxins.…”

Section: Discussionmentioning

confidence: 99%

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

et al. 2016

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Toxic shock syndrome toxin 1 (TSST-1) is a Staphylococcus aureus superantigen that has been implicated in both menstrual and nonmenstrual toxic shock syndrome (TSS). Despite the important role of TSST-1 in severe human disease, a comprehensive understanding of staphylococcal regulatory factors that control TSST-1 expression remains incomplete. The S. aureus exotoxin expression (Sae) operon contains a well-characterized two-component system that regulates a number of important exotoxins in S. aureus, although regulation of TSST-1 by the Sae system has not been investigated. We generated a defined deletion mutant of the Sae histidine kinase sensor (saeS) in the prototypic menstrual TSS strain S. aureus MN8. Mutation of saeS resulted in a complete loss of TSST-1 expression. Using both luciferase reporter experiments and quantitative real-time PCR, we demonstrate that the Sae system is an important transcriptional activator of TSST-1 expression. Recombinant SaeR was able to bind directly to the tst promoter to a region containing two SaeR consensus binding sites. Although the stand-alone SarA transcriptional regulator has been shown to be both a positive and a negative regulator of TSST-1, deletion of sarA in S. aureus MN8 resulted in a dramatic overexpression of TSST-1. As expected, mutation of agr also reduced TSST-1 expression, but this phenotype appeared to be independent of Sae. A double mutation of saeS and sarA resulted in the loss of TSST-1 expression. This work indicates that the Sae system is a dominant and direct transcriptional activator that is required for expression of TSST-1. IMPORTANCEThe TSST-1 superantigen is an exotoxin, produced by some strains of S. aureus, that has a clear role in both menstrual and nonmenstrual TSS. Although the well-characterized agr quorum sensing system is a known positive regulator of TSST-1, the molecular mechanisms that directly control TSST-1 expression are only partially understood. Our studies demonstrate that the Sae two-component regulatory system is a positive transcriptional regulator that binds directly to the TSST-1 promoter, and furthermore, our data suggest that Sae is required for expression of TSST-1. This work highlights how major regulatory circuits can converge to fine-tune exotoxin expression and suggests that the Sae regulatory system may be an important target for antivirulence strategies. Staphylococcus aureus is both a common commensal of humans and a prominent bacterial pathogen that is responsible for an assortment of illnesses ranging from self-limiting superficial infections to life-threatening invasive diseases (1). While most infections caused by S. aureus involve the coordinated expression of numerous virulence factors, a few select diseases, including staphylococcal scalded skin syndrome, food poisoning, and toxic shock syndrome (TSS), require the expression of specific staphylococcal exotoxins (2).Staphylococcal TSS is a rare but devastating disease that is caused by S. aureus strains that secrete high levels of superantigens. Super...

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Section: Discussionmentioning

confidence: 99%

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

et al. 2016

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“…A markerless in-frame deletion of tet38 (SAUSA300_0139), encoding a major facilitator efflux pump, was constructed using pKOR-1 according to established protocols (25,38). Briefly, sequences flanking the tet38 locus were amplified by PCR using primers tet38-5=F and tet38-5=R to generate the upstream arm and primers tet38-3=F and tet38-3=R to generate the downstream arm.…”

Section: Methodsmentioning

confidence: 99%

“…Techniques for genetic manipulation of S. aureus were conducted according to established guidelines (32) and as described in our previous work (24,25,33). The University of Nebraska transposon mutant library (34) was used as a source of transposon insertions that inactivated SAUSA300_2490 (NE1393) and SAUS300_2489 (NE2336).…”

Section: Methodsmentioning

confidence: 99%

“…We subsequently noted that when S. aureus cultures were supplemented with a trilinolein triglyceride substrate, Geh activity quickly liberated growth-inhibitory concentrations of linoleic acid (25). Moreover, 50 M free linoleic acid imposed a 10-to 12-h growth delay in cultures of S. aureus USA300, which was then followed by unimpeded exponential growth; similar results were obtained with 50 M trilinolein in wild-type geh-proficient S. aureus USA300, whereas growth of a geh-deficient mutant was unaffected by 50 M trilinolein (24,25). From these observations, we hypothesized that, in addition to the induction of expression of secreted proteases, there should also be an inducible mechanism for resistance of S. aureus to linoleic acid.…”

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confidence: 99%

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Inducible Expression of a Resistance-Nodulation-Division-Type Efflux Pump in Staphylococcus aureus Provides Resistance to Linoleic and Arachidonic Acids

et al. 2015

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Although Staphylococcus aureus is exposed to antimicrobial fatty acids on the skin, in nasal secretions, and in abscesses, a specific mechanism of inducible resistance to this important facet of innate immunity has not been identified. Here, we have sequenced the genome of S. aureus USA300 variants selected for their ability to grow at an elevated concentration of linoleic acid. The fatty acid-resistant clone FAR7 had a single nucleotide polymorphism resulting in an H 121 Y substitution in an uncharacterized transcriptional regulator belonging to the AcrR family, which was divergently transcribed from a gene encoding a member of the resistance-nodulation-division superfamily of multidrug efflux pumps. We named these genes farR and farE, for regulator and effector of fatty acid resistance, respectively. Several lines of evidence indicated that FarE promotes efflux of antimicrobial fatty acids and is regulated by FarR. First, expression of farE was strongly induced by arachidonic and linoleic acids in an farRdependent manner. Second, an H 121 Y substitution in FarR resulted in increased expression of farE and was alone sufficient to promote increased resistance of S. aureus to linoleic acid. Third, inactivation of farE resulted in a significant reduction in the inducible resistance of S. aureus to the bactericidal activity of 100 M linoleic acid, increased accumulation of [ 14 C]linoleic acid by growing cells, and severely impaired growth in the presence of nonbactericidal concentrations of linoleic acid. Cumulatively, these findings represent the first description of a specific mechanism of inducible resistance to antimicrobial fatty acids in a Gram-positive pathogen. IMPORTANCEStaphylococcus aureus colonizes approximately 25% of humans and is a leading cause of human infectious morbidity and mortality. To persist on human hosts, S. aureus must have intrinsic defense mechanisms to cope with antimicrobial fatty acids, which comprise an important component of human innate defense mechanisms. We have identified a novel pair of genes, farR and farE, that constitute a dedicated regulator and effector of S. aureus resistance to linoleic and arachidonic acids, which are major fatty acids in human membrane phospholipid. Expression of farE, which encodes an efflux pump, is induced in an farRdependent mechanism, in response to these antimicrobial fatty acids that would be encountered in a tissue abscess. Staphylococcus aureus has a dichotomous relation with human hosts, being able to establish an asymptomatic commensal relationship, but is also historically known as a leading cause of human infectious morbidity and mortality. Significantly, death attributed to S. aureus in the United States is now comparable to mortality rates for AIDS, tuberculosis, and viral hepatitis (1-3). Not surprisingly, therefore, S. aureus has been the subject of intensive research on mechanisms of pathogenesis and acquisition and transfer of antibiotic resistance and of efforts to identify potential vaccine antigens (4-6). Until the late ...

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“…At this time it is still speculative whether a cholesterol esterase produced by P. aeruginosa [88] may represent an additional virulence factor aiding in the inactivation of host-derived antimicrobial cholesteryl esters. Of interest is the recent finding of Cadieux et al [89] who identified a lipase in a hypervirulent community-associated methicillin-resistant S. aureus strain USA300 that hydrolyzes triglycerides and liberates the free fatty acid linoleic acid with growth inhibitory activity against S. aureus. It is possible that the liberation of antibacterial linoleic acid is primarily targeted against other bacteria thereby conferring growth advantage to S. aureus.…”

Section: Bacterial Mechanisms That Manipulate Host-derived Lipidsmentioning

confidence: 99%

Antimicrobial lipids: Emerging effector molecules of innate host defense

Porter

Daniel²,

Alvarez³

et al. 2015

WJI

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The antimicrobial properties of host-derived derived lipids have become increasingly recognized and evidence is mounting that antimicrobial lipids (AMLs), like antimicrobial peptides, are effector molecules of the innate immune system and are regulated by its conserved pathways. This review, with primary focus on the human body, provides some background on the biochemistry of lipids, summarizes their biological functions, expands on their antimicrobial properties and site-specific composition, presents modes of synergism with antimicrobial peptides, and highlights the more recent reports on the regulation of AML production as well as bacterial resistance mechanisms. Based on extant data a concept of innate epithelial defense is proposed where epithelial cells, in response to microbial products and proinflammatory cytokines and through activation of conserved innate signaling pathways, increase their lipid uptake and up-regulate transcription of enzymes involved in antimicrobial lipid biosynthesis, and induce transcription of antimicrobial peptides as well as cytokines and chemokines. The subsequently secreted antimicrobial peptides and lipids then attack and eliminate the invader, assisted by or in synergism with other antimicrobial molecules delivered by other defense cells that have been recruited to the site of infection, in most of the cases. This review invites

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Role of Lipase from Community-Associated Methicillin-Resistant Staphylococcus aureus Strain USA300 in Hydrolyzing Triglycerides into Growth-Inhibitory Free Fatty Acids

Cited by 76 publications

References 67 publications

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

Inducible Expression of a Resistance-Nodulation-Division-Type Efflux Pump in Staphylococcus aureus Provides Resistance to Linoleic and Arachidonic Acids

Antimicrobial lipids: Emerging effector molecules of innate host defense

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