title: Oxygen-dependent phenotypic variation in group A streptococcus.
abstract: BACKGROUND
  The phenotypic heterogeneity of the human pathogen Streptococcus pyogenes [group A streptococcus (GAS)] is associated with bacterial virulence variation. During invasive GAS infection, mutations in the two-component regulatory system covR/covS leads to increases in hyaluronic acid capsule production, virulence genes expression, and lethality in the mouse infection model. Phenotypic variation of GAS is also found under in vitro culture conditions. However, whether a specific environmental factor is important for phenotypic variation is still unknown.
  
  
  METHODS
  GAS968 is an emm12-type clinical isolate that converts from mucoid to hypermucoid morphology under in vitro culture conditions. To clarify whether morphology variation can be triggered by specific environmental signals, or whether different morphology variants would be selected under specific environmental stresses, GAS968 was cultured under different conditions, and the changes in the number of mucoid and hypermucoid colonies in the total bacterial population were analyzed.
  
  
  RESULTS
  The ratio of mucoid and hypermucoid colonies of GAS968 in the total bacterial population changes dramatically under aerobic and anaerobic conditions. The decrease in the number of hypermucoid colonies in the total bacterial population under aerobic conditions is not caused by growth repression, suggesting that the morphology conversion of GAS968 is inhibited by oxygen.
  
  
  CONCLUSIONS
  Phenotypic heterogeneity has been shown to contribute to invasive GAS infection. Our results suggest that oxygen-dependent morphology variation in GAS968 may have important roles in bacterial pathogenesis.
authors: Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan. Electronic address: entchuan@gap.cgu.edu.tw.
authors: Chuan
authors: C
authors: Chiang-Ni
authors: Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.
authors: Siao-Ying
authors: SY
authors: Nian
authors: Department of Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.
authors: Jiunn-Jong
authors: JJ
authors: Wu
authors: Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital and Children's Hospital, Tao-Yuan, Taiwan.
authors: Chih-Jung
authors: CJ
authors: Chen
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics*; D005947:Glucose / Q000378:metabolism; D000071677:Histidine Kinase; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000032:analysis / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D019344:Lactic Acid / Q000378:metabolism; D051379:Mice; D006899:Mixed Function Oxygenases / Q000096:biosynthesis; D009154:Mutation / Q000235:genetics; D010100:Oxygen / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics*; D013290:Streptococcal Infections / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C432143:CsrR protein, Streptococcus pyogenes; D047908:Intracellular Signaling Peptides and Proteins; D011135:Polysaccharides, Bacterial; D012097:Repressor Proteins; D019344:Lactic Acid; D006820:Hyaluronic Acid; D006861:Hydrogen Peroxide; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase; C534547:CovS protein, Streptococcus pyogenes; D000071677:Histidine Kinase; D005947:Glucose; D010100:Oxygen
keywords: group A streptococcus; mucoid; oxygen; phenotypic variation