Prophages in Host-Associated Microbes: The Most Abundant Symbiosis on Earth and Its Relevance in Marine Holobionts

Bacteriophages are the most abundant biological entity on the planet, the most numerous members of any given food web, and key players in carbon and nutrient cycling. Temperate bacteriophages can incorporate into the genome of their bacterial host and remain there in a mutualistic fashion. These prophages typically encode functions that determine the ecology of their bacterial host, often in beneficial ways such as protection against protist predation, nutrient acquisition, carbohydrate utilization, and superinfection immunity from other phages. Here we surveyed prophages and their functional genomic content in a large database of host-associated bacteria from marine environments around the globe. Strikingly, we observed that host-associated bacteria characterized as pathogens contained significantly higher abundances of prophages in their assembled genomes than non-pathogenic host-associated marine bacteria. This specific trend has been observed in human systems, in the context of human bacterial pathogens and non-pathogenic human associated bacteria. Our data suggests that this trend is prevalent in marine environments across a variety of ecosystems and animals. We are now extending these bioinformatic approaches to understand the abundance and functional profiles of prophages in metagenomic profiles of marine holobionts to understand their role in coral reef benthic communities.