1887

Abstract

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. This study demonstrates that the synthesis and length distribution of the 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 Δ 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 polymerase gene expression in the Δ mutant. Complementation of this mutant with the 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 in the wild-type strain resulted in production of a large amount of high-molecular-mass OAg molecules. An increased dosage of either or also altered OAg chain-length distribution. Transcription of and genes was regulated during bacterial growth but in an RfaH-independent manner. Overall, these findings indicate that expression of the , and genes is finely regulated to determine an appropriate balance between the proteins responsible for polymerization and chain-length distribution of OAg.

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2007-10-01
2020-04-06
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