Bacteriophages (phages or bacterial viruses) are the most abundant biological entities
in our planet; their influence reaches far beyond the microorganisms they parasitize.
Phages are present in every environment and shape up every bacterial population in both active
and passive ways. They participate in the circulation of organic matter and drive the evolution
of microorganisms by horizontal gene transfer at unprecedented scales. The mass flow
of genetic information in the microbial world influences the biosphere and poses challenges
for science and medicine. The genetic flow, however, depends on the fate of the viral DNA
injected into the bacterial cell. The archetypal notion of phages only engaging in predatorprey
relationships is slowly fading. Because of their varied development cycles, environmental
conditions, and the diversity of microorganisms they parasitize, phages form a dense
and highly complex web of dependencies, which has important consequences for life on
Earth. The sophisticated phage-bacteria interplay includes both aggressive action (bacterial
lysis) and “diplomatic negotiations” (prophage domestication). Here, we review the most important
mechanisms of interactions between phages and bacteria and their evolutionary consequences
influencing their biodiversity.
Keywords: Bacteriophages, microbial evolution, horizontal gene transfer, biodiversity, phage life cycle, parasites.
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