Program

Viruses are the most abundant biological entities in the ocean. They have been recognized as an important biological factor that influences the abundance, diversity and productivity of various microbial fractions in the sea. Picocyanobacteria of the genera Synechococcus and Prochlorococcus are the most abundant primary producers in the ocean. The community of picocyanobacteria is highly structured, with diverse genetic lineages being associated to specific ecological traits. Cyanobacterial viruses (cyanophages) that infect Synechococcus and Prochlorococcus have been extensively investigated on the topics of physiology, genomics, ecology and phage-host interaction. All known marine cyanophages are tailed double-stranded DNA viruses, belonging to three well-defined bacteriophage families: Myoviridae, Podoviridae and Siphoviridae. We investigated the biogeographic distribution patterns of cyanopodoviruses and cyanomyoviruses throughout the global ocean. Our results showed that cyanopodoviruses and cyanomyoviruses are both abundant in various marine environments and that Cluster MPP-B, II and III appear to be the most dominant lineages. Cyanopodoviruses and Cluster I and IV cyanomyoviruses exhibited habitat-related variability in relative abundance, while Cluster II and III cyanomyoviruses appeared to be consistently dominant in various habitats. Synechococcus phages and Prochlorococcus phages have distinct distribution patterns, which were significantly correlated to those of Synechococcus and Prochlorococcus, respectively. We also observed a strong correlation between community compositions of cyanophages and picocyanobacteria. Given that cyanomyoviruses tend to have a broad host range and some can cross-infect Synechococcus and Prochlorococcus while cyanopodoviruses are commonly host-specific, the observation that their community compositions both significantly correlated to that of picocyanobacteria was unexpected. Although cyanomyoviruses and cyanopodoviruses differ in host specificity, their biogeographic distributions are likely both constrained by the picocyanobacterial community.