Interesting data were observed especially in the comparison of symbiotic and pathogenetic bacteria. In the reconstruction using Fix proteins, the pathogenic and symbiotic species are more related to each other, except for FixABC. In this topology, the high reliability Antiinfection Compound Library screening values associated with branches hint at least two possible moments of independent horizontal transfer events. In one moment, a horizontal transfer event would

have occurred in X. autotrophicus and approximated this nitrogen-fixing methylotrophic bacteria to the non-photosynthetic symbiont group; and in another moment, two other independent events would have occurred between the nitrogen-fixing symbionts R. etli – M. loti and R. leguminosarum – E. meliloti. In the topology built with the TrbCFGIJ proteins, a closer proximity

between bioremediation bacteria, pathogenic, symbiotic, and non-symbiotic nitrogen-fixing bacteria was observed. TrbCFGIJ compose the trb operon, whose proteins form a membrane-associated macromolecular complex involved in mating-pair formation, facilitating the DNA transfer from donor to recipient cells [40]. The database built in this study shows that in the genomes of the bioremediatiors Mesorhizobium BNC1 and R. palustris, of the symbionts A. caulinodans and B. japonicum and of the methylotrophic nitrogen-fixing bacteria X. autotrophicus, there are transposases, integrases, and/or hypothetical proteins next to the TrbCFGIJ proteins, contrarily to the pathogenic O. anthropi. This observation suggests that these proteins may have been acquired through DNA transposition and/or integration mechanisms associated with horizontal gene transfer events, which occurred Aurora Kinase inhibitor in the common ancestor of these species, and that other events of gene transfer may have occurred in O. anthropi, leading to its divergence from the other pathogens analyzed. In NodN, as well as before in FixH, FixNOP, VirB8, VirB9, and VirB10 topologies, the phylogenetic relationship observed between M. loti and the Brucella-Bartonella pathogens is corroborated by Paulsen et al. (2002) [3], which showed that B. suis presents high similarity to R. tumefaciens, E. meliloti, and M. loti, sharing extensive syntenic regions with the

latter. Since NodN was the only nodulation protein present in all pathogens analyzed, in R. radiobacter, in photosynthetic nitrogen-fixing symbionts and other symbionts and in Aurantimonas, it is possible that this protein: i) has been acquired in an event preceding the separation between photosynthetic symbionts and pathogens, being lost in A. caulinodans, X. autotrophicus, and Mesorhizobium BNC1; or ii) that these organisms acquired this protein after the divergence between photosynthetic symbionts and pathogens, in a more recent horizontal transfer event. There is very little information about NodN. In R. leguminosarum, nodN is induced in response to flavonone molecules and this induction is nodD-dependent [41], and in both R. leguminosarum and E.