title: Cell surface of Lactococcus lactis is covered by a protective polysaccharide pellicle.
abstract: In Gram-positive bacteria, the functional role of surface polysaccharides (PS) that are not of capsular nature remains poorly understood. Here, we report the presence of a novel cell wall PS pellicle on the surface of Lactococcus lactis. Spontaneous PS-negative mutants were selected using semi-liquid growth conditions, and all mutations were mapped in a single chromosomal locus coding for PS biosynthesis. PS molecules were shown to be composed of hexasaccharide phosphate repeating units that are distinct from other bacterial PS. Using complementary atomic force and transmission electron microscopy techniques, we showed that the PS layer forms an outer pellicle surrounding the cell. Notably, we found that this cell wall layer confers a protective barrier against host phagocytosis by murine macrophages. Altogether, our results suggest that the PS pellicle could represent a new cell envelope structural component of Gram-positive bacteria.
authors.affiliation: INRA, UMR1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Chapot-Chartier
authors.forename: Evgeny
authors.initials: E
authors.lastname: Vinogradov
authors.forename: Irina
authors.initials: I
authors.lastname: Sadovskaya
authors.forename: Guillaume
authors.initials: G
authors.lastname: Andre
authors.forename: Michel-Yves
authors.initials: MY
authors.lastname: Mistou
authors.forename: Patrick
authors.initials: P
authors.lastname: Trieu-Cuot
authors.forename: Sylviane
authors.initials: S
authors.lastname: Furlan
authors.forename: Elena
authors.initials: E
authors.lastname: Bidnenko
authors.forename: Pascal
authors.initials: P
authors.lastname: Courtin
authors.forename: Christine
authors.initials: C
authors.lastname: Péchoux
authors.forename: Pascal
authors.initials: P
authors.lastname: Hols
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
authors.forename: Saulius
authors.initials: S
authors.lastname: Kulakauskas
mesh_terms: D001422:Bacterial Adhesion; D016667:Bacterial Capsules / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002240:Carbohydrate Sequence; D002473:Cell Wall / Q000737:chemistry*; D002478:Cells, Cultured; D002876:Chromosomes, Bacterial; D013294:Lactococcus lactis / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000382:microbiology; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D010587:Phagocytosis / Q000502:physiology*; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial