HrpM is involved in glucan synthesis, biofilm formation and pathogenicity of Xanthomonas axonopodis pv. citri

CONFORTE VP; MALAMUD F; HOMEM R; MARANO MR; CASTAGNARO AP; DO AMARAL AM

Congreso; SAIB; 2010

One of the most devastating citrus diseases is bacterial citrus canker caused by Xanthomonas axonopodis pv citri (Xac). Previous work from our laboratory demonstrated that Xac is able to form biofilm communities in biotic and abiotic surfaces. To obtain new genes involved in Xac biofilm formation we performed a screening using a library of 6000 Tn5 mutants. Mutants with fewer adherence than the wild-type strain to polystyrene surface after 16 hours of growth in Y-minimal medium were chosen. One of the mutant obtained from the screening corresponded to an insertion in hrpM gene, encoding a glucosyltransferase enzyme. According to hrpM gene homology with identified sequences in other bacteria, it is a candidate for the cyclic beta-1,2-glucan synthesis in Xac. Here we demostrated that the disruption of this gene compromised the production of the cyclic beta-(1,2)-glucan. Moreover, this mutant showed reduced swimming motility and biofilm development. Bacterial suspensions were inoculated in lemon and grapefruitplants. No disease symptoms were observed in leaves infected with hrpM strain.