Abstract
The Roseobacter clade is abundant and widespread in marine environments and plays an important role in oceanic biogeochemical cycling. In this present study, a lytic siphophage (labeled vB_DshS-R5C) infecting the strain type of Dinoroseobacter shibae named DFL12T, which is part of the Roseobacter clade, was isolated from the oligotrophic South China Sea. Phage R5C showed a narrow host range, short latent period and low burst size. The genome length of phage R5C was 77, 874 bp with a G+C content of 61.5%. Genomic comparisons detected no genome matches in the GenBank database and phylogenetic analysis based on DNA polymerase I revealed phylogenetic features that were distinct to other phages, suggesting the novelty of R5C. Several auxiliary metabolic genes (e.g., phoH gene, heat shock protein and queuosine biosynthesis genes) were identified in the R5C genome that may be beneficial to the host and/or offer a competitive advantage for the phage. Among siphophages infecting the Roseobacter clade (roseosiphophages), four gene transfer agent-like genes were commonly located with close proximity to structural genes, suggesting that their function may be related to the tail of siphoviruses. The isolation and characterization of R5C demonstrated the high genomic and physiological diversity of roseophages as well as improved our understanding of host–phage interactions and the ecology of the marine Roseobacter.
Highlights
As the most abundant biological entities, viruses play an important role in nutrient cycles and energy flow in marine environments through viral lysis [1]
Transmission Electron Microscopy (TEM) showed that the phage R5C had a long hexagon head that measured about 114 ± 2 nm in length and 70 ± 2 nm for the greatest width in addition to a flexional long tail with a length of 142 ± 2 nm (Figure 1b)
Was resistant to all three concentrations of chloroform. These results indicated the absence of lipids in the capsid or the surrounding lipid layer, which has commonly been observed among all of the roseophages isolated so far
Summary
As the most abundant biological entities, viruses play an important role in nutrient cycles and energy flow in marine environments through viral lysis [1]. Viruses are one of the major contributors to horizontal gene transfer and evolution of their hosts, with approximately 1023 infections occurring every second in seawater [2]. Recent investigations of viruses using metagenomics fundamentally changed our estimation of their diversity and community structure as well as our understanding of their interaction with their hosts [3]. It is proposed and demonstrated that this problem can be partially solved by the isolation and genetic characterization of viruses, especially those that infect dominant bacterial groups, such as Synechococcus and Vibrio in coastal areas, in addition to SAR 11 and Prochlorococcus in open ocean [4,5,6,7,8]. The physiological and ecological characterization of Viruses 2017, 9, 109; doi:10.3390/v9050109 www.mdpi.com/journal/viruses
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