Distribution and Evolution of the Bacteriophage WO and Its Antagonism With .

The symbiosis system comprising eukaryotic hosts, intracellular bacterium , and temperate bacteriophages WO is widely spread through nearly half the number of arthropod species. The relationships between the three components of the system are extremely intricate. Even though the bacteriophage WO can have diverse influences on the ecology and evolution of , little is known about the distribution and evolution of the phages. To the best of our knowledge, this study is the first to report that in infected fig wasps (, , and ), the genomes of all the strains had only one cryptic WO prophage, which contained defects in the genomic structural modules. This phenomenon was contrary to the widely accepted understanding that with cryptic prophages usually possesses at least one intact WO prophage consisting of gene sequences of the head, baseplate, and tail modules, through which the prophage could form intact virions. In addition to the genetic structure features, the phylogenetic relationships of WO and also revealed that bacteriophage WO can horizontally spread among a certain genus or a group of insect hosts, nearly free from the restriction of the affiliation of . Combined with the vertical transmission along with , the wide spread of WO phages can be explained. Furthermore, the gender preference and functional module preference for transcriptional activity of the genes in cryptic WOs implied the antagonized coevolutionary pattern between WO prophages and their hosts.