ROLE OF C-DI-GMP IN Xanthomonas vesicatoria VIRULENCE

PONSO MA; MARTINO R; ROMERO AM; SMANIA AM; BIANCO MI; YARYURA PM

Chapadmalal, Buenos Aires

Congreso; XVIII Congreso Sociedad Argentina de Microbiologia General; 2023

Sociedad Argentina de Microbiología General (SAMIGE)

Xanthomonas vesicatoria (Xv) is a member of a complex of species that causes bacterial spot on tomato (Solanum lycopersicum). Currently, little is known about several virulence factors and its regulation in Xv. Bis-(3´→5´)-cyclic dimeric guanosine monophosphate (c-diGMP) is a second messenger involved in numerous bacterial functions including motility, biofilm formation, adhesion and virulence. C-di-GMP levels are regulated by two types of enzymes: ones with diguanylate cyclase (DGC) activity and others with phosphodiesterase (PDE) activity. The first ones are responsible for synthesizing c-di-GMP and the second ones for degrading it. Previously, three native Xv strains were isolated from tomato plants presenting bacterial spot disease at different levels. The most virulent strain (208-WT) showed a well-established, homogeneous and mature biofilm. It also presented a more viscous xanthan (principal exopolysaccharide) with longer xanthan chains than the other two strains. Here, in order to obtain Xv strains with high (208-DGC) and low (208-PDE) cdi-GMP levels, 208-WT was transformed with plasmids coding for a DGC and PDE proteins, respectively. Both strains were characterized performing in vitro assays to evaluate extracellular enzymes production (cellulase and protease), motility (swimming and swarming) and bacterial adhesion. Then, virulence assays were carried out on tomato plants. The strain 208-PDE showed significantly higher cellulase activity compared with 208-DGC and 208-WT, while no significant differences were observed in protease activity. Moreover, 208-DGC showed reduced motility exhibiting less swimming and swarming. However, 208-DGC showed the highest bacterial adhesion compared to 208-PDE. In addition, 208-PDE strain caused more lesions on tomato plants than 208-WT and 208-DGC. The last one caused fewer lesions than the other two strains. All of these results are in concordance with those reported in other bacterial species. However, since the action of the second messenger is poorly understood in Xv, further studies are needed to fully characterize the functions and cellular mechanisms in which c-di-GMP may be involved.