title: Functional analysis of an unusual type IV pilus in the Gram-positive Streptococcus sanguinis.
abstract: Type IV pili (Tfp), which have been studied extensively in a few Gram-negative species, are the paradigm of a group of widespread and functionally versatile nano-machines. Here, we performed the most detailed molecular characterisation of Tfp in a Gram-positive bacterium. We demonstrate that the naturally competent Streptococcus sanguinis produces retractable Tfp, which like their Gram-negative counterparts can generate hundreds of piconewton of tensile force and promote intense surface-associated motility. Tfp power 'train-like' directional motion parallel to the long axis of chains of cells, leading to spreading zones around bacteria grown on plates. However, S. sanguinis Tfp are not involved in DNA uptake, which is mediated by a related but distinct nano-machine, and are unusual because they are composed of two pilins in comparable amounts, rather than one as normally seen. Whole genome sequencing identified a locus encoding all the genes involved in Tfp biology in S. sanguinis. A systematic mutational analysis revealed that Tfp biogenesis in S. sanguinis relies on a more basic machinery (only 10 components) than in Gram-negative species and that a small subset of four proteins dispensable for pilus biogenesis are essential for motility. Intriguingly, one of the piliated mutants that does not exhibit spreading retains microscopic motility but moves sideways, which suggests that the corresponding protein controls motion directionality. Besides establishing S. sanguinis as a useful new model for studying Tfp biology, these findings have important implications for our understanding of these widespread filamentous nano-machines.
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
authors.forename: Ishwori
authors.initials: I
authors.lastname: Gurung
authors.affiliation: Department of Biology, Brooklyn College of the City University of New York, New York, NY, USA.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Spielman
authors.affiliation: The Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK.|Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Davies
authors.affiliation: Department of Biology, Brooklyn College of the City University of New York, New York, NY, USA.
authors.forename: Rajan
authors.initials: R
authors.lastname: Lala
authors.affiliation: Department of Microbiology, Oslo University Hospital, Oslo, Norway.
authors.forename: Peter
authors.initials: P
authors.lastname: Gaustad
authors.affiliation: Department of Biology, Brooklyn College of the City University of New York, New York, NY, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Biais
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Pelicic
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism*; D013291:Streptococcus / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D036781:Fimbriae Proteins