O-antigen modal chain length in Shigella flexneri 2a is growth-regulated through RfaH-mediated transcriptional control of the wzy gene

Javier A Carter, Carlos J Blondel, Mercedes Zaldívar, Sergio A Alvarez, Cristina L Marolda, Miguel A Valvano, Inés Contreras

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

Shigella flexneri 2a 2457T produces lipopolysaccharide (LPS) with two O-antigen (OAg) chain lengths: a short (S-OAg) controlled by WzzB and a very long (VL-OAg) determined by Wzz(pHS-2). This study demonstrates that the synthesis and length distribution of the S. flexneri OAg are under growth-phase-dependent regulation. Quantitative electrophoretic analysis showed that the VL-OAg increased during growth while the S-OAg distribution remained constant. Increased production of VL-OAg correlated with the growth-phase-regulated expression of the transcription elongation factor RfaH, and was severely impaired in a DeltarfaH mutant, which synthesized only low-molecular-mass OAg molecules and a small amount of S-OAg. Real-time RT-PCR revealed a drastic reduction of wzy polymerase gene expression in the DeltarfaH mutant. Complementation of this mutant with the wzy gene cloned into a high-copy-number plasmid restored the bimodal OAg distribution, suggesting that cellular levels of Wzy influence not only OAg polymerization but also chain-length distribution. Accordingly, overexpression of wzy in the wild-type strain resulted in production of a large amount of high-molecular-mass OAg molecules. An increased dosage of either wzzB or wzz(pHS-2) also altered OAg chain-length distribution. Transcription of wzzB and wzz(pHS-2) genes was regulated during bacterial growth but in an RfaH-independent manner. Overall, these findings indicate that expression of the wzy, wzzB and wzz(pHS-2) genes is finely regulated to determine an appropriate balance between the proteins responsible for polymerization and chain-length distribution of S. flexneri OAg.
Original languageEnglish
Pages (from-to)3499-507
Number of pages9
JournalMicrobiology (Reading, England)
Volume153
Issue numberPt 10
DOIs
Publication statusPublished - Oct 2007

ASJC Scopus subject areas

  • Microbiology

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