The Myxococcus xanthus wbgB gene encodes a glycosyltransferase homologue required for lipopolysaccharide O-antigen biosynthesis

Myxococcus xanthus is a,gram-negative soil bacterium that initiates a compl ex developmental program in response to starvation. A transposon insertion (Tn5-lac Omega 109) mutant with developmental deficiencies was isolated and characterized in this study. A strain containing this insertion mutation i n an otherwise wild-type background showed delayed developmental aggregatio n for about 12 h and sporulated at 1-2% of the wild-type level. Tn5-lac Ome ga 109 was found to have disrupted the M. xanthus wbgB gene, which is locat ed 2.1 kb downstream of the M. xanthus lipopolysacharide (LPS) O-antigen bi osynthesis genes wzm wzt wbgA. The deduced polypeptide sequence of WbgB sha res significant similarity with bacterial glycosyltransferases including hi . xanthus WbgA, The wbgB::Tn5-lac Omega 109 mutant was found to be defectiv e in LPS O-antigen synthesis by immunochemical analysis. Further mutational analysis indicated that the defects of the wbgB::Tn5-lac Omega 109 mutant were not the result of polar effects on downstream genes, Various motility assays demonstrated that the Tn5-lac Omega 109 mutation affected both socia l (S) and adventurous (A) gliding motility of M. xanthus cells. The pleiotr ophic effects of wbgB mutations indicate the importance of LPS O-antigen bi osynthesis for various cellular functions in M. xanthus.