Abstract
BackgroundMarine phages are spectacularly diverse in nature. Dozens of roseophages infecting members of Roseobacter clade bacteria were isolated and characterized, exhibiting a very high degree of genetic diversity. In the present study, the induction of two temperate bacteriophages, namely, vB_ThpS-P1 and vB_PeaS-P1, was performed in Roseobacter clade bacteria isolated from the deep-sea water, Thiobacimonas profunda JLT2016 and Pelagibaca abyssi JLT2014, respectively. Two novel phages in morphological, genomic and proteomic features were presented, and their phylogeny and evolutionary relationships were explored by bioinformatic analysis.ResultsElectron microscopy showed that the morphology of the two phages were similar to that of siphoviruses. Genome sequencing indicated that the two phages were similar in size, organization, and content, thereby suggesting that these shared a common ancestor. Despite the presence of Mu-like phage head genes, the phages are more closely related to Rhodobacter phage RC1 than Mu phages in terms of gene content and sequence similarity. Based on comparative genomic and phylogenetic analysis, we propose a Mu-like head phage group to allow for the inclusion of Mu-like phages and two newly phages. The sequences of the Mu-like head phage group were widespread, occurring in each investigated metagenomes. Furthermore, the horizontal exchange of genetic material within the Mu-like head phage group might have involved a gene that was associated with phage phenotypic characteristics.ConclusionsThis study is the first report on the complete genome sequences of temperate phages that infect deep-sea roseobacters, belonging to the Mu-like head phage group. The Mu-like head phage group might represent a small but ubiquitous fraction of marine viral diversity.
Highlights
Marine phages are spectacularly diverse in nature
Phage Induction and Morphology T. profunda JLT2016 growth was apparently inhibited after the addition of mitomycin C at the exponential growth phase, whereas that of virus-like particles (VLPs) rapidly increased to 4.9 × 1010 particles/mL after 15 h (Fig. 1A and B)
The two transposable prophages were not induced at a high temperature (42 °C), whereas the transposable coliphage Mu is usually induced by high temperature rather than mitomycin C [32]
Summary
Dozens of roseophages infecting members of Roseobacter clade bacteria were isolated and characterized, exhibiting a very high degree of genetic diversity. The induction of two temperate bacteriophages, namely, vB_ThpS-P1 and vB_PeaS-P1, was performed in Roseobacter clade bacteria isolated from the deep-sea water, Thiobacimonas profunda JLT2016 and Pelagibaca abyssi JLT2014, respectively. Dozens of phages infecting RCB are isolated and sequenced, including those of roseophages SIO1 [11, 12], DSS3Φ2 [8], EE36Φ1 [8],ΦCB2047-B [13, 14], RDJLΦ1 [15, 16], P12053L [17], RPP1 and RLP1 [18], and vB_DshP-R1 [19, 20]. TM1040 harbor one and three mitomycin C-inducible prophages, respectively [21, 22]
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