Prophages ticking time bombs or key genetic elements in bacterial hosts?
In the marine environment, 30-40 % of the bacteria are infected and killed by bacteriophages, and the interactions between phages and bacteria are central to the ecology and evolution of marine microbial communities with significant effects on biogeochemical cycles. Following infection, lytic phages hijack the cellular machinery of the bacteria to produce new phages and kill the host, whereas temperate phages integrate their genome into the host chromosome, where it remains dormant (prophage) until conditions favor its reactivation and lysis of the host cell. The prophage genome represents a potential metabolic burden and molecular time bomb in the host genome which at any time can induce and kill its host. Temperate phages also have direct influence on the genetic composition and architecture of the host since the incorporated phage genome is replicated along with the host genome4. Consequently, prophages can potentially enrich the host cell with new beneficial genes, for example by encoding virulence factors in pathogenic bacteria. The capacity of phages to encode virulence properties and disseminate these among marine Vibrio communities needs to be explored for improving understanding of the role of phages as drivers of virulence in this bacterial group. The overall objective of the project is to decipher the genetic mechanisms and environmental controls of phage-driven virulence by quantifying phage-mediated transformation of harmless Vibrio bacteria into pathogens of humans, fish, shellfish and corals. Such research will provide new insight on phage influence on dynamics and dispersal of virulence in the marine environment