Artículo de revista
O-antigen modal chain length in Shigella flexneri 2a is growth-regulated through RfaH-mediated transcriptional control of the wzy gene
Fecha
2007-10Registro en:
MICROBIOLOGY-SGM 153: 3499-3507 Part: 10
1350-0872
Autor
Carter Jaña, Javier Antonio
Blondel, Carlos
Zaldívar San Román, María Mercedes
Álvarez Armijo, Sergio Aníbal
Marolda, Cristina L.
Valvano, Miguel A.
Contreras, Inés
Institución
Resumen
Shigella flexneri 2a 2457T produces lipopolysaccharide (LIPS) 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 Delta rfaH 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 Delta rfaH 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 wzzpHS-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.