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dc.contributor.authorHooven, T.A.
dc.contributor.authorCatomeris, A.J.
dc.contributor.authorBonakdar, M.
dc.date.accessioned2019-06-05T18:28:18Z
dc.date.available2019-06-05T18:28:18Z
dc.date.issued2018
dc.identifier.urihttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85039561657&doi=10.1128%2fIAI.00612-17&partnerID=40&md5=4701492be03b656ee605e6c1a0666068
dc.identifier.urihttp://hdl.handle.net/10713/9446
dc.description.abstractStreptococcus agalactiae (group B Streptococcus [GBS]) causes serious infections in neonates. We previously reported a transposon sequencing (Tn-seq) system for performing genomewide assessment of gene fitness in GBS. In order to identify molecular mechanisms required for GBS to transition from a mucosal commensal lifestyle to bloodstream invasion, we performed Tn-seq on GBS strain A909 with human whole blood. Our analysis identified 16 genes conditionally essential for GBS survival in blood, of which 75% were members of the capsular polysaccharide (cps) operon. Among the non-cps genes identified as conditionally essential was relA, which encodes an enzyme whose activity is central to the bacterial stringent response—a conserved adaptation to environmental stress. We used blood coincubation studies of targeted knockout strains to confirm the expected growth defects of GBS deficient in capsule or stringent response activation. Unexpectedly, we found that the relA knockout strains demonstrated decreased expression of β-hemolysin/cytolysin, an important cytotoxin implicated in facilitating GBS invasion. Furthermore, chemical activation of the stringent response with serine hydroxamate increased β-hemolysin/cytolysin expression. To establish a mechanism by which the stringent response leads to increased cytotoxicity, we performed transcriptome sequencing (RNA-seq) on two GBS strains grown under stringent response or control conditions. This revealed a conserved decrease in the expression of genes in the arginine deiminase pathway during stringent response activation. Through coincubation with supplemental arginine and the arginine antagonist canavanine, we show that arginine availability is a determinant of GBS cytotoxicity and that the pathway between stringent response activation and increased virulence is arginine dependent. Copyright 2017 American Society for Microbiology.en_US
dc.description.sponsorshipThis work was supported by NIH/NIAID grants number R01 AI092743, R33 AI098654, and R21 AI111020 to A.J.R., John M. Driscoll, Jr., M.D. Children's Fund (Columbia University Department of Pediatrics), and the Pediatric Scientist Development Program (NIH/NICHD grant number K12 HD000850) to T.A.H.en_US
dc.description.urihttps://dx.doi.org/10.1128/IAI.00612-17en_US
dc.language.isoen-USen_US
dc.publisherAmerican Society for Microbiologyen_US
dc.relation.ispartofInfection and Immunity
dc.subjectBloodstream infectionsen_US
dc.subjectStreptococcus agalactiaeen_US
dc.subjectTn-seqen_US
dc.titleThe Streptococcus agalactiae stringent response enhances virulence and persistence in human blooden_US
dc.typeArticleen_US
dc.identifier.doi10.1128/IAI.00612-17
dc.identifier.pmid29109175


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