| Abstrakt: |
ABSTRACTResistance profiles of the two BordetellaspeciesB. bronchisepticaand B. pertussisagainst various antimicrobial peptides were determined in liquid survival and agar diffusion assays. B. bronchisepticaexhibited significantly higher resistance against all tested peptides thanB. pertussis. The most powerful agents acting on B. bronchisepticawere, in the order of their killing efficiencies, cecropin P > cecropin B > magainin-II-amide > protamine > melittin. Interestingly, for B. bronchiseptica, the resistance level was significantly affected by phase variation, as a bvgSdeletion derivative showed an increased sensitivity to these peptides. Tn5-induced protamine-sensitive B. bronchisepticamutants, which were found to be very susceptible to most of the cationic peptides, were isolated. In two of these mutants, the genetic loci inactivated by transposon insertion were identified as containing genes highly homologous to the wlbAand wlbLgenes ofB. pertussisthat are involved in the biosynthesis of lipopolysaccharide (LPS). In agreement with this finding, the two peptide-sensitive mutants revealed structural changes in the LPS, resulting in the loss of the O-specific side chains and the prevalence of the LPS core structure. This demonstrates that LPS plays a major role in the resistance of B. bronchisepticaagainst the action of antimicrobial peptides and suggests that B. pertussisis much more susceptible to these peptides due to the lack of the highly charged O-specific sugar side chains. |
