Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, Maryland, USA.
Environ Microbiol. 2023 Dec;25(12):3349-3363. doi: 10.1111/1462-2920.16525. Epub 2023 Oct 20.
Picocyanobacteria contribute greatly to offshore primary production with cells extending through the deep euphotic zone. Literature indicates high viral infection of cyanobacteria in ocean transition zones. We postulate that the bottom of the euphotic zone is a transition zone, where communities transition from phototrophic to aphotic processes. We use single-copy core genes to examine cyanophage to cyanobacteria ratios in cellular metagenomes in the subtropical North Atlantic and Pacific. Cyanophage to cyanobacteria terL/rpoB ratios generally increase to >10 in the deep euphotic zone. As light levels decrease in the fall, Prochlorococcus in the deep euphotic zone experience reduced light levels. We find clear differences between spring (Geotraces GA02) and fall (GA03) in the North Atlantic, with terL/rpoB ratios increasing to >40 in the fall. When examining 23 months of the North Pacific Hawaii Ocean Timeseries, the depth of elevated cyanophage to cyanobacteria ratios in cellular metagenomes negatively correlated with surface photosynthetic radiation (PAR), particularly with the change in PAR, which reflected the season. In fall, all picocyanobacteria ecotypes were found at depths enriched with viruses, while in summer, only low light ecotypes were affected. Thus, we find high cyanophage infection both in the deep euphotic zone and during seasonal transitions.
微藻在近海初级生产力中贡献巨大，其细胞延伸至深光照区。文献表明，海洋过渡区的蓝藻病毒感染率很高。我们假设，光照区的底部是一个过渡区，生物群落从光合作用向无光过程过渡。我们使用单拷贝核心基因来检测亚热带北大西洋和太平洋细胞宏基因组中的噬藻体与蓝藻的比例。噬藻体与蓝藻 terL/rpoB 的比值通常在深光照区增加到>10。随着秋季光照水平的下降，深光照区的聚球藻经历光照水平的降低。我们发现北大西洋春季（Geotraces GA02）和秋季（GA03）之间存在明显差异，秋季 terL/rpoB 的比值增加到>40。在检查北太平洋夏威夷海洋时间序列的 23 个月时，细胞宏基因组中升高的噬藻体与蓝藻的比值与表层光合辐射（PAR）呈负相关，特别是与反映季节变化的 PAR 变化呈负相关。在秋季，所有的小型蓝藻生态型都在富含病毒的深度处被发现，而在夏季，只有低光生态型受到影响。因此，我们发现深光照区和季节性过渡区都存在高噬藻体感染。
