title: Secreted single-stranded DNA is involved in the initial phase of biofilm formation by Neisseria gonorrhoeae.
abstract: Neisseria gonorrhoeae is an obligate human pathogen that colonizes the genital tract and causes gonorrhoea. Neisseria gonorrhoeae can form biofilms during natural cervical infections, on glass and in continuous flow-chamber systems. These biofilms contain large amounts of extracellular DNA, which plays an important role in biofilm formation. Many clinical isolates contain a gonococcal genetic island that encodes a type IV secretion system (T4SS). The T4SS of N. gonorrhoeae strain MS11 secretes ssDNA directly into the medium. Biofilm formation, studied in continuous flow-chamber systems by confocal laser scanning microscopy (CLSM), was strongly reduced, especially in the initial phases of biofilm formation, in the presence of Exonuclease I, which specifically degrades ssDNA or in a ΔtraB strain that does not secrete ssDNA. To specifically detect ssDNA in biofilms using CLSM, a novel method was developed in which thermostable fluorescently labelled ssDNA- and ss/dsDNA-binding proteins were used to visualize ssDNA and total DNA in biofilms and planktonic cultures. Remarkably, mainly dsDNA was detected in biofilms of the ssDNA secreting strain. We conclude that the secreted ssDNA facilitates initial biofilm formation, but that the secreted ssDNA is not retained in mature biofilms.
authors.affiliation: Department of Ecophysiology, Max-Planck-Institute for terrestrial Microbiology, Marburg, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Zweig
authors.forename: Sabine
authors.initials: S
authors.lastname: Schork
authors.forename: Andrea
authors.initials: A
authors.lastname: Koerdt
authors.forename: Katja
authors.initials: K
authors.lastname: Siewering
authors.forename: Claus
authors.initials: C
authors.lastname: Sternberg
authors.forename: Kai
authors.initials: K
authors.lastname: Thormann
authors.forename: Sonja-Verena
authors.initials: SV
authors.lastname: Albers
authors.forename: Søren
authors.initials: S
authors.lastname: Molin
authors.forename: Chris
authors.initials: C
authors.lastname: van der Does
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D004247:DNA / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000494:pharmacology; D018613:Microscopy, Confocal; D009344:Neisseria gonorrhoeae / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004247:DNA; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I