title: A novel protein, RafX, is important for common cell wall polysaccharide biosynthesis in Streptococcus pneumoniae: implications for bacterial virulence.
abstract: Teichoic acid (TA), together with peptidoglycan (PG), represents a highly complex glycopolymer that ensures cell wall integrity and has several crucial physiological activities. Through an insertion-deletion mutation strategy, we show that ΔrafX mutants are impaired in cell wall covalently attached TA (WTA)-PG biosynthesis, as evidenced by their abnormal banding patterns and reduced amounts of WTA in comparison with wild-type strains. Site-directed mutagenesis revealed an essential role for external loop 4 and some highly conserved amino acid residues in the function of RafX protein. The rafX gene was highly conserved in closely related streptococcal species, suggesting an important physiological function in the lifestyle of streptococci. Moreover, a strain D39 ΔrafX mutant was impaired in bacterial growth, autolysis, bacterial division, and morphology. We observed that a strain R6 ΔrafX mutant was reduced in adhesion relative to the wild-type R6 strain, which was supported by an inhibition assay and a reduced amount of CbpA protein on the ΔrafX mutant bacterial cell surface, as shown by flow cytometric analysis. Finally, ΔrafX mutants were significantly attenuated in virulence in a murine sepsis model. Together, these findings suggest that RafX contributes to the biosynthesis of WTA, which is essential for full pneumococcal virulence.
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Kaifeng
authors.initials: K
authors.lastname: Wu
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China Department of Laboratory Medicine, The First Affiliated Hospital, Zunyi Medical College, Zunyi, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Wenchun
authors.initials: W
authors.lastname: Xu
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Xu
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Libin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
authors.forename: Ju
authors.initials: J
authors.lastname: Cao
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China apoe@163.com yibingyin56@126.com.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Diagnostic Medicine (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China apoe@163.com yibingyin56@126.com.
authors.forename: Yibing
authors.initials: Y
authors.lastname: Yin
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010457:Peptidoglycan / Q000378:metabolism; D011008:Pneumococcal Infections / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D013682:Teichoic Acids / Q000378:metabolism; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D010457:Peptidoglycan; D011135:Polysaccharides, Bacterial; D013682:Teichoic Acids