Marine Bacteriophages

Abstract

Bacteriophages, or phages, are viruses infecting bacteria. In the marine environment, free phage particles are generally one order of magnitude more abundant than bacterial cells. Phages shape microbial community structure and composition, through viral cell lysis, and they influence host metabolism, most remarkably through auxiliary metabolic genes, and host evolution, through horizontal gene transfer. Marine phage diversity is tremendous and just being explored. Cultivation-independent studies, especially those taking advantage of the significant developments in sequencing technologies, allow the characterization of phage genomic diversity in environmental samples. On the other hand, working with isolated phage-host systems allows in-depth characterization of virion morphology and structure, phage-host interactions, co-evolution of phages and hosts. The first section of this book article, entitled “Genomic diversity of marine phages and how do we study it”, focuses on sequencing-based studies of environmental phages and their main finding regarding genomic diversity. The second section, entitled “Cultivated phages infecting main groups of marine bacteria”, reviews the diversity of marine phage isolates. The last section, “Marine phage ecology”, covers main ecological concepts, as for example phage micro- and macro-diversity, phages as mortality factors and the viral shunt, diel rhythms of phage infections and auxiliary metabolic genes.