The vast metabolic diversity amongst Alphaproteobacteria encourages to explore the impact of phages on the phenotype of those bacteria and their abilities to adapt to diverse environmental conditions. In the midst of nearly 380 genera of Alphaproteobacteria we can distinguish phototrophic (e.g. Rhodobacter spp.), methylotrophic (e.g. Paracoccus spp.), endosymbiotic (e.g. Wolbachia spp.) and parasitic bacteria (e.g. Rickettsia spp.). There are also many representatives of Alphaproteobacteria of biotechnological value, e.g. rhizobia, useful in agriculture as they are capable of transforming atmospheric nitrogen into fixed nitrogen, which can be then utilized by plants; several denitrifying species; as well as bacteria like Agrobacterium tumefaciens that can transfer exogenous DNA into plants’ cells, which find application in molecular biology.
Although, our knowledge about Alphaproteobacteria is vast, still only little is known about their phages. Presented meta-analysis aims to collect all publicly available data concerning Alphaproteobacteria phages, to provide sufficient, detailed and dedicated public database of those viruses. During the exploration not only active phages were analyzed, but additionally 319 completed Alphaproteobacteria genomes were screened for the presence of prophage sequences using bioinformatic tools. As the result, we were able to find 78 “active” phages, 277 prophage sequences and 90 gene transfer agents (GTA). All identified elements were subjected to thorough comparative genomic, phylogenetic, phylogenomic and similarity networks building analyses.
Studying of the collected data, gave us an insight into an overall diversity of Alphaproteobacteria phages and enabled to find relations between particular mobile genetic elements which create separate clusters within the similarity networks. The systemic approach enabled also identification of unique and auxiliary genetic information carried by particular phages and revealed how it relates with hosts’ characteristics. Finally, it allowed to draw some general conclusions concerning phage evolution, e.g. the positive correlation between the number of prophages and the size of the host genome.