Structure analysis of lipid A species in Vibrio parahaemolyticus by constructing mutants lacking multiple secondary acyltransferases of lipid A.

Four secondary acyltransferases of Vibrio parahaemolyticus lipid A encoded by VP_RS00880, VP_RS08405, VP_RS12170, and VP_RS01045 have been identified. In this study, mutants of V. parahaemolyticus were constructed by deleting two, three, or four of these genes. The double mutants showed similar growth pattern with the wild-type, but the quadruple mutant VPW011 showed significant growth defect at both 37°C and 21°C. Lipid A samples were extracted from these mutants and analyzed by electrospray ionization-mass spectrometry. The double and triple mutants could synthesize hepta- and octa-acylated lipid A species, while the quadruple mutant VPW011 could synthesize hexa- and hepta-acylated lipid A. The results suggest that the four secondary acyltransferases could complement each other in V. parahaemolyticus. More importantly, additional secondary acyltransferases of lipid A might exist in V. parahaemolyticus and their activities might be as strong as the four known secondary acyltransferases. The unusual multiple secondary acyltransferases of lipid A might play roles in pathogenicity and antimicrobic resistance of V. parahaemolyticus.