Cell wall teichoic acid glycosylation in Listeria monocytogenes serotype 4b requires gtcA, a novel, serogroup-specific gene

We have identified a novel gene, gtcA, involved in the decoration of cell w all teichoic acid of Listeria monocytogenes serotype 4b with galactose and glucose. Insertional inactivation of gtcA brought about loss of reactivity with the serotype 4b-specific monoclonal antibody c74.22 and was accompanie d by a complete lack of galactose and a marked reduction in the amounts of glucose on teichoic acid. Interestingly, the composition of membrane-associ ated lipoteichoic acid was not affected. Complementation of the mutants wit h the cloned gtcA in trans restored galactose and glucose on teichoic acid to wild-type levels. The complemented strains also recovered reactivity wit h c74.22. Within L. monocytogenes, sequences homologous to gtcA were found in all serogroup 4 isolates but not in strains of any other serotypes, In s erotype 4b, gtcA appears to be the first member of a bicistronic operon whi ch includes a gene with homology to Bacillus subtilis rpmE, encoding riboso mal protein L31. In contrast to gtcA, the latter gene appears conserved amo ng all screened serotypes of L. monocytogenes.