Identification of a Gene Cluster for the Biosynthesis of a Long, Galactose-Rich Exopolysaccharide in Lactobacillus rhamnosus GG and Functional Analysis of the Priming Glycosyltransferase.
Cell surface polysaccharides have an established role as virulence factors in human bacterial pathogens. Less documented are the biosynthesis and biological functions of surface polysaccharides in beneficial bacteria. We identified a gene cluster that encodes the enzymes and regulatory and transporter proteins for the different steps in the biosynthesis of extracellular polysaccharides (EPS) of the well-documented probiotic strain Lactobacillus rhamnosus GG. Subsequent mutation of the welE gene, encoding the priming glycosyltransferase within this cluster, and comparative phenotypic analyses of wild-type versus mutant strains confirmed the specific function of this gene cluster in the biosynthesis of high-molecular-weight, galactose-rich heteropolymeric EPS molecules. The phenotypic analyses included monomer composition determination, estimation of the polymer length of the isolated EPS molecules, and single-molecule force spectroscopy of the surface polysaccharides. Further characterization of the welE mutant also showed that deprivation of these long, galactose-rich EPS molecules results in an increased adherence and biofilm formation capacity of L. rhamnosus GG, possibly because of less shielding of adhesins such as fimbria-like structures.
Centre of Microbial and Plant Genetics, K.U. Leuven, Kasteelpark Arenberg, Belgium.
Sarah
S
Lebeer
Tine L A
TL
Verhoeven
Grégory
G
Francius
Geert
G
Schoofs
Ivo
I
Lambrichts
Yves
Y
Dufrêne
Jos
J
Vanderleyden
Sigrid C J
SC
De Keersmaecker
D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D053898:Biosynthetic Pathways / Q000235:genetics*; D018938:Caco-2 Cells; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005690:Galactose / Q000032:analysis; D055786:Gene Knockout Techniques; D023061:Gene Order; D005816:Genetic Complementation Test; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D052201:Lacticaseibacillus rhamnosus / Q000201:enzymology* / Q000235:genetics* / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000737:chemistry; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D016695:Glycosyltransferases; D005690:Galactose