[Bacterial viruses in the Anthropocene era: friends or enemies of their hosts ?].

Bacterial viruses, or bacteriophages, are the most abundant viruses on Earth, and their hosts are the most widespread living organisms in the biosphere. They are found in a free state, as virions, but are also very abundant in bacterial genomes, as prophages. Bacteriophages are present in all biotopes colonized by bacteria, such as water, soils, extreme environments, human, animal, and plant microbiomes, where they contribute to genetic exchanges. Therefore, all factors affecting these environments have a major impact on the dynamics of bacterial populations and their viruses.