Characterization and genomic analysis of Stutzerimonas stutzeri phage vB_PstS_ZQG1, representing a novel viral genus.

Stutzerimonas stutzeri is an opportunistic pathogenic bacterium belonging to the Gammaproteobacteria, exhibiting wide distribution in the environment and playing significant ecological roles such as nitrogen fixation or pollutant degradation. Despite its ecological importance, only two S. stutzeri phages have been isolated to date. Here, a novel S. stutzeri phage, vB_PstS_ZQG1, was isolated from the surface seawater of Qingdao, China. Transmission electron microscopy analysis indicates that vB_PstS_ZQG1 has a morphology characterized by a long non-contractile tail. The genomic sequence of vB_PstS_ZQG1 contains a linear, double-strand 61,790-bp with the G+C content of 53.24% and encodes 90 putative open reading frames. Two auxiliary metabolic genes encoding TolA protein and nucleotide pyrophosphohydrolase were identified, which are likely involved in host adaptation and phage reproduction. Phylogenetic and comparative genomic analyses demonstrated that vB_PstS_ZQG1 exhibits low similarity with previously isolated phages or uncultured viruses (average nucleotide identity values range from 21.7 to 29.4), suggesting that it represents a novel viral genus by itself, here named as Fuevirus. Biogeographic analysis showed that vB_PstS_ZQG1 was only detected in epipelagic and mesopelagic zone with low abundance. In summary, our findings of the phage vB_PstS_ZQG1 will provide helpful insights for further research on the interactions between S. stutzeri phages and their hosts, and contribute to discovering unknown viral sequences in the metagenomic database.

Distributions and relationships of virio- and picoplankton in the epi-, meso- and bathypelagic zones of the Amundsen Sea, West Antarctica during the austral summer.

Virioplankton and picoplankton are the most abundant marine biological entities on earth and mediate biogeochemical cycles in the Southern Ocean. However, understanding of their distribution and relationships with environmental factors is lacking. Here, we report on their distribution and relationships with environmental factors at 48 stations from 112.5° to 150°W and 67° to 75.5°S in the Amundsen Sea of West Antarctica. The epipelagic stations were grouped into four clusters based on the virio- and picoplankton composition and abundance. Clusters three and four, which were associated with the ice-edge blooms in the coastal and Amundsen Sea Polynya (ASP) areas, had high abundances of autotrophic picoeukaryotes; this resulted in subsequent high abundances of heterotrophic prokaryotes and viruses. Cluster two stations were in open oceanic areas, where the abundances of autotrophic and heterotrophic picoplankton were low. Cluster one stations were located between the areas of blooms and the oceanic areas, which had a low abundance of heterotrophic prokaryotes and picoeukaryotes and a high abundance of virioplankton. The abundance of viruses was significantly correlated with the abundances of autotrophic picoeukaryotes and Chl-a concentration in oceanic areas, although this reflected a time-lag with autotrophic picoeukaryote and heterotrophic prokaryotes abundances in ice-edge bloom areas. The upwelling of Circumpolar Deep Water (CDW) might have induced the high abundance of autotrophic picoeukaryotes in the epipelagic zone, and the sinking particulate organic carbon (POC) might have induced the high abundance of heterotrophic prokaryotes and virioplankton in the meso- and bathypelagic zones. This study shows that the summer distribution of virio- and picoplankton in the Amundsen Sea of West Antarctica was mainly controlled by upwelling of the CDW and the timing of ice-edge blooms.