Modification of lipopolysaccharide with colanic acid (M-antigen) repeats in Escherichia coli.
Colanic acid (CA) or M-antigen is an exopolysaccharide produced by many enterobacteria, including the majority of Escherichia coli strains. Unlike other capsular polysaccharides, which have a close association with the bacterial surface, CA forms a loosely associated saccharide mesh that coats the bacteria, often within biofilms. Herein we show that a highly mucoid strain of E. coli K-12 ligates CA repeats to a significant proportion of lipopolysaccharide (LPS) core acceptor molecules, forming the novel LPS glycoform we call MLPS.MLPS biosynthesis is dependent upon (i) CA induction, (ii) LPS core biosynthesis, and (iii) the O-antigen ligase WaaL. Compositional analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy of a purified MLPS sample confirmed the presence of a CA repeat unit identical in carbohydrate sequence, but differing at multiple positions in anomeric configuration and linkage, from published structures of extracellular CA. The attachment point was identified as O-7 of the L-glycero-D-manno-heptose of the outer LPS core, the same position used for O-antigen ligation. When O-antigen biosynthesis was restored in the K-12 background and grown under conditions meeting the above specifications, only MLPS was observed, suggesting E. coli can reversibly change its proximal covalently linked cell surface polysaccharide coat from O-antigen to CA in response to certain environmental stimuli. The identification of MLPS has implications for potential underlying mechanisms coordinating the synthesis of various surface polysaccharides.
Meredith
Timothy C
TC
Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1065, USA.
Mamat
Uwe
U
Kaczynski
Zbigniew
Z
Lindner
Buko
B
Holst
Otto
O
Woodard
Ronald W
RW
D000942:Antigens, Bacterial / Q000378:metabolism*; D001422:Bacterial Adhesion; D002240:Carbohydrate Sequence; D004926:Escherichia coli / Q000378:metabolism*; D017353:Gene Deletion; D008070:Lipopolysaccharides / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D019081:O Antigens / Q000378:metabolism*; D009844:Oligosaccharides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000378:metabolism
D000942:Antigens, Bacterial; D008070:Lipopolysaccharides; D019081:O Antigens; D009844:Oligosaccharides; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; C004275:colanic acid