J Bacteriol. 2014 Jul 7. pii: JB.01696-14. [Epub ahead of print]
A novel protein RafX is important for common cell wall polysaccharide biosynthesis in Streptococcus pneumoniae: implications for bacterial virulence.
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Abstract
Teichoic acid (TA), together with peptidoglycan (PG), represents a highly complex glycopolymer to ensure cell wall integrity and has several crucial physiological activities. Through insertion-deletion mutation strategy, we show that ΔrafX mutants were impaired in WTA-PG biosynthesis as evidenced by the abnormal banding pattern and reduced amount of wall teichoic acid in comparison with wild type strains. Site-directed mutagenesis revealed an essential role for the external loop 4 and some highly conserved amino acid residues for the function of RafX protein. rafX gene was highly conserved in closely related streptococcal species, suggesting an important physiological function in the lifestyle of streptococci. Moreover, D39 ΔrafX mutant was impaired in bacterial growth, autolysis as well as bacterial division and morphology. We observed that R6 ΔrafX mutant was reduced in adhesion relative to the wild type R6 strain, which was supported by the inhibition assay and a reduced amount of CbpA protein on the bacterial surface of ΔrafX mutants shown by flow cytometric analysis. Finally, ΔrafX mutants were significantly attenuated in virulence in murine sepsis model. Together these findings suggest that RafX contributes to the biosynthesis of wall teichoic acid which is essential for full pneumococcal virulence.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
PMID: 25002545 [PubMed - as supplied by publisher]
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