Ureaplasma diversum protein interaction networks: evidence of horizontal gene transfer and evolution of reduced genomes among Mollicutes.

Abstract

Ureaplasma diversum is a member of the Mollicutes class responsible for urogenital tract infection in cattle and small ruminants. Studies indicate that the process of horizontal gene transfer, the exchange of genetic material among different species, has a crucial role in mollicute evolution, affecting the group's characteristic genomic reduction process and simplification of metabolic pathways. Using bioinformatics tools and the STRING database of known and predicted protein interactions, we constructed the protein-protein interaction network of U. diversum and compared it with the networks of other members of the Mollicutes class. We also investigated horizontal gene transfer events in subnetworks of interest involved in purine and pyrimidine metabolism and urease function, chosen because of their intrinsic importance for host colonization and virulence. We identified horizontal gene transfer events among Mollicutes and from Ureaplasma to Staphylococcus aureus and Corynebacterium, bacterial groups that colonize the urogenital niche. The overall tendency of genome reduction and simplification in the Mollicutes is echoed in their protein interaction networks, which tend to be more generalized and less selective. Our data suggest that the process was permitted (or enabled) by an increase in host dependence and the available gene repertoire in the urogenital tract shared via horizontal gene transfer.