title: Group B streptococcal haemolysin and pigment, a tale of twins.
abstract: Group B streptococcus [(GBS or Streptococcus agalactiae)] is a leading cause of neonatal meningitis and septicaemia. Most clinical isolates express simultaneously a β-haemolysin/cytolysin and a red polyenic pigment, two phenotypic traits important for GBS identification in medical microbiology. The genetic determinants encoding the GBS haemolysin and pigment have been elucidated and the molecular structure of the pigment has been determined. The cyl operon involved in haemolysin and pigment production is regulated by the major two-component system CovS/R, which coordinates the expression of multiple virulence factors of GBS. Genetic analyses indicated strongly that the haemolysin activity was due to a cytolytic toxin encoded by cylE. However, the biochemical nature of the GBS haemolysin has remained elusive for almost a century because of its instability during purification procedures. Recently, it has been suggested that the haemolytic and cytolytic activity of GBS is due to the ornithine rhamnopolyenic pigment and not to the CylE protein. Here we review and summarize our current knowledge of the genetics, regulation and biochemistry of these twin GBS phenotypic traits, including their functions as GBS virulence factors.
authors.affiliation: Service of Microbiology, Hospital Virgen de las Nieves, Granada, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Rosa-Fraile
authors.forename: Shaynoor
authors.initials: S
authors.lastname: Dramsi
authors.forename: Barbara
authors.initials: B
authors.lastname: Spellerberg
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D005810:Multigene Family / Q000235:genetics; D009876:Operon / Q000235:genetics; D010860:Pigments, Biological / Q000235:genetics / Q000378:metabolism; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000235:genetics / Q000502:physiology*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D010860:Pigments, Biological; D037521:Virulence Factors; C071495:streptococcal group B hemolysin
keywords: GBS; Group B streptococcus; Streptococcus agalactiae; granadaene; hemolysin; pigment