title: Dynamic capsule restructuring by the main pneumococcal autolysin LytA in response to the epithelium.
abstract: Bacterial pathogens produce complex carbohydrate capsules to protect against bactericidal immune molecules. Paradoxically, the pneumococcal capsule sensitizes the bacterium to antimicrobial peptides found on epithelial surfaces. Here we show that upon interaction with antimicrobial peptides, encapsulated pneumococci survive by removing capsule from the cell surface within minutes in a process dependent on the suicidal amidase autolysin LytA. In contrast to classical bacterial autolysis, during capsule shedding, LytA promotes bacterial survival and is dispersed circumferentially around the cell. However, both autolysis and capsule shedding depend on the cell wall hydrolytic activity of LytA. Capsule shedding drastically increases invasion of epithelial cells and is the main pathway by which pneumococci reduce surface bound capsule during early acute lung infection of mice. The previously unrecognized role of LytA in removing capsule to combat antimicrobial peptides may explain why nearly all clinical isolates of pneumococci conserve this enzyme despite the lethal selective pressure of antibiotics.
authors.affiliation: Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee 38103, USA.
authors.forename: Colin C
authors.initials: CC
authors.lastname: Kietzman
authors.affiliation: Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee 38103, USA.
authors.forename: Geli
authors.initials: G
authors.lastname: Gao
authors.affiliation: Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee 38103, USA.
authors.forename: Beth
authors.initials: B
authors.lastname: Mann
authors.affiliation: Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee 38103, USA.
authors.forename: Lance
authors.initials: L
authors.lastname: Myers
authors.affiliation: Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee 38103, USA.
authors.forename: Elaine I
authors.initials: EI
authors.lastname: Tuomanen
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D016667:Bacterial Capsules / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000502:physiology*; D005260:Female; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D051379:Mice; D009154:Mutation; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics / Q000378:metabolism*; D011008:Pneumococcal Infections / Q000382:microbiology; D011018:Pneumonia, Pneumococcal / Q000382:microbiology / Q000473:pathology; D013296:Streptococcus pneumoniae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009238:N-Acetylmuramoyl-L-alanine Amidase