Abstract
Bacteriophages have a significant impact on the structure and function of marine microbial communities. Phages of some major bacterial lineages have recently been shown to dominate the marine viral communities. However, phages that infect many important bacterial clades still remained unexplored. Members of the marine OM43 clade are methylotrophs that play important roles in C1 metabolism. OM43 phages (phages that infect the OM43 bacteria) represent an understudied viral group with only one known isolate. In this study, we describe the genomic characterization and biogeography of an OM43 phage that infects the strain HTCC2181, designated MEP301. MEP301 has a genome size of 34,774 bp. We found that MEP301 is genetically distinct from other known phage isolates and only displays significant sequence similarity with some metagenomic viral genomes (MVGs). A total of 12 MEP301-type MVGs were identified from metagenomic datasets. Comparative genomic and phylogenetic analyses revealed that MEP301-type phages can be separated into two subgroups (subgroup I and subgroup II). We also performed a metagenomic recruitment analysis to determine the relative abundance of reads mapped to these MEP301-type phages, which suggested that subgroup I MEP301-type phages are present predominantly in the cold upper waters with lower salinity. Notably, subgroup II phages have an inverse different distribution pattern, implying that they may infect hosts from a distinct OM43 subcluster. Our study has expanded the knowledge about the genomic diversity of marine OM43 phages and identified a new phage group that is widespread in the ocean.
Highlights
Viruses play an important role in the marine microbial loop and biogeochemical cycles (Fuhrman, 1999; Suttle, 2005, 2007)
Owing to the tremendous advance in cultured-independent technologies, such as metagenomics (Hurwitz and Sullivan, 2013; Mizuno et al, 2013; Brum et al, 2015; Paez-Espino et al, 2016; Gregory et al, 2019; Beaulaurier et al, 2020; Luo et al, 2020) and single-cell genomics (Roux et al, 2014; Labonté et al, 2015; Martinez-Hernandez et al, 2017), a comprehensive understanding of the viral community structure and diversity has emerged and many viral genome fragments have been obtained from these analyses
OM43 phage MEP301 was isolated from coastal surface water of Yantai, Bohai sea, China (N37°28', E121°28')
Summary
Viruses play an important role in the marine microbial loop and biogeochemical cycles (Fuhrman, 1999; Suttle, 2005, 2007). They are the most abundant and genetically diverse biological entities in the ocean, with average abundance of an order of magnitude more than that of bacteria (Suttle, 2007; Güemes et al, 2016). Most marine viruses are bacteriophages that infect bacteria (Fuhrman, 1999; Wommack and Colwell, 2000). Most metagenomic viral sequences lack cultured counterparts that hamper the understanding of the ecological roles and biological traits of marine viruses. Other than the abovementioned phages, phages infecting many important marine bacteria still remain poorly investigated
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