Roles of Lipopolysaccharide Glycosyltransferases in Maintenance of Morphology, Cell Wall Permeability, and Antimicrobial Susceptibilities.

has a unique lipopolysaccharide structure that is essential in maintaining its cell envelope integrity and imbues the bacterium with natural resistance to cationic antimicrobial peptides (CAMPs). Our group has recently elucidated the complete set of LPS glycosyltransferase genes in reference strain G27. Here, with a series of eight systematically constructed LPS glycosyltransferase gene mutants (G27Δ, G27Δ, G27Δ, G27Δ, G27Δ, G27Δ, G27Δ and G27Δ), we investigated the roles of LPS glycosyltransferases in maintaining cell morphology, cell wall permeability, and antimicrobial susceptibilities. We demonstrated that deletion of these LPS glycosyltransferase genes did not interfere with bacterial cell wall permeability, but resulted in significant morphological changes (coccoid, coiled "c"-shape, and irregular shapes) after 48 h growth as compared to the rod-like cell shape of the wild-type strain. Moreover, as compared with the wild-type, none of the LPS mutants had altered susceptibility against clarithromycin, levofloxacin, amoxicillin, tetracycline, and metronidazole. However, the deletion of the conserved LPS glycosyltransferases, especially the O-antigen-initiating enzyme WecA, displayed a dramatic increase in susceptibility to the CAMP polymyxin B and rifampicin. Taken together, our findings suggest that the LPS glycosyltransferases play critical roles in the maintenance of the typical spiral morphology of , as well as resistance to CAMPs and rifampicin. The LPS glycosyltransferases could be promising targets for developing novel anti- drugs.