Cell surface of Lactococcus lactis is covered by a protective polysaccharide pellicle.
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.
Chapot-Chartier
Marie-Pierre
MP
INRA, UMR1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France.
Vinogradov
Evgeny
E
Sadovskaya
Irina
I
Andre
Guillaume
G
Mistou
Michel-Yves
MY
Trieu-Cuot
Patrick
P
Furlan
Sylviane
S
Bidnenko
Elena
E
Courtin
Pascal
P
Péchoux
Christine
C
Hols
Pascal
P
Dufrêne
Yves F
YF
Kulakauskas
Saulius
S
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
D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial