Role of the Group B Antigen of Streptococcus agalactiae: A Peptidoglycan-Anchored Polysaccharide Involved in Cell Wall Biogenesis

PLoS Pathogens

Michel-Yves Mistou¹  Christine Péchoux¹  Pascal Courtin²  Shaynoor Dramsi²  Patrick Trieu-Cuot³  Saulius Kulakauskas³  Élise Caliot⁴  Marie-Pierre Chapot-Chartier⁴ 

[1] AgroParisTech, UMR MICALIS, Jouy-en-Josas, France;CNRS ERL 3526, Unité des Bactéries Pathogènes à Gram positif, Paris, France;INRA, UMR1319, MICALIS, Jouy-en-Josas, France;Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France

关键词: Streptococcus agalactiae;    Cell walls;    Staphylococcus aureus;    Phosphates;    Complement system;    Polysaccharides;    Biosynthesis;    Vancomycin;   

DOI  :  10.1371/journal.ppat.1002756

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Streptococcus agalactiae (Group B streptococcus, GBS) is a leading cause of infections in neonates and an emerging pathogen in adults. The Lancefield Group B carbohydrate (GBC) is a peptidoglycan-anchored antigen that defines this species as a Group B Streptococcus. Despite earlier immunological and biochemical characterizations, the function of this abundant glycopolymer has never been addressed experimentally. Here, we inactivated the gene gbcO encoding a putative UDP-N-acetylglucosamine-1-phosphate:lipid phosphate transferase thought to catalyze the first step of GBC synthesis. Indeed, the gbcO mutant was unable to synthesize the GBC polymer, and displayed an important growth defect in vitro. Electron microscopy study of the GBC-depleted strain of S. agalactiae revealed a series of growth-related abnormalities: random placement of septa, defective cell division and separation processes, and aberrant cell morphology. Furthermore, vancomycin labeling and peptidoglycan structure analysis demonstrated that, in the absence of GBC, cells failed to initiate normal PG synthesis and cannot complete polymerization of the murein sacculus. Finally, the subcellular localization of the PG hydrolase PcsB, which has a critical role in cell division of streptococci, was altered in the gbcO mutant. Collectively, these findings show that GBC is an essential component of the cell wall of S. agalactiae whose function is reminiscent of that of conventional wall teichoic acids found in Staphylococcus aureus or Bacillus subtilis. Furthermore, our findings raise the possibility that GBC-like molecules play a major role in the growth of most if not all beta –hemolytic streptococci.

【 授权许可】

CC BY