The marine picoeukaryote Bathycoccus prasinos has been considered a cosmopolitan alga, although recent studies indicate two ecotypes exist, Clade BI (B. prasinos) and Clade BII. Viruses that infect Bathycoccus Clade BI are known (BpVs), but not that infect BII. We isolated three dsDNA prasinoviruses from the Sargasso Sea against Clade BII isolate RCC716. The BII-Vs do not infect BI, and two (BII-V2 and BII-V3) have larger genomes (~210 kb) than BI-Viruses and BII-V1. BII-Vs share ~90% of their proteins, and between 65% to 83% of their proteins with sequenced BpVs. Phylogenomic reconstructions and PolB analyses establish close-relatedness of BII-V2 and BII-V3, yet BII-V2 has 10-fold higher infectivity and induces greater mortality on host isolate RCC716. BII-V1 is more distant, has a shorter latent period, and infects both available BII isolates, RCC716 and RCC715, while BII-V2 and BII-V3 do not exhibit productive infection of the latter in our experiments. Global metagenome analyses show Clade BI and BII algal relative abundances correlate positively with their respective viruses. The distributions delineate BI/BpVs as occupying lower temperature mesotrophic and coastal systems, whereas BII/BII-Vs occupy warmer temperature, higher salinity ecosystems. Accordingly, with molecular diagnostic support, we name Clade BII Bathycoccus calidus sp. nov. and propose that molecular diversity within this new species likely connects to the differentiated host-virus dynamics observed in our time course experiments. Overall, the tightly linked biogeography of Bathycoccus host and virus clades observed herein supports species-level host specificity, with strain-level variations in infection parameters.

海洋微小核生物 Bathycoccus prasinos被认为是一种世界性藻类，尽管最近的研究表明存在两种生态型，即 Clade BI ( B. prasinos ) 和 Clade BII。感染深球菌的病毒进化枝 BI 是已知的 (BpVs)，但并不感染 BII。我们从马尾藻海中分离出三种 dsDNA prasinoviruses 对抗 Clade BII 分离株 RCC716。BII-V 不感染 BI，其中两个（BII-V2 和 BII-V3）具有比 BI-Viruses 和 BII-V1 更大的基因组（~210 kb）。BII-V 共享约 90% 的蛋白质，65% 至 83% 的蛋白质与测序的 BpV 共享。系统基因组重建和 PolB 分析确定了 BII-V2 和 BII-V3 的密切相关性，但 BII-V2 的感染性高出 10 倍，并在宿主分离株 RCC716 上诱导更高的死亡率。BII-V1 距离更远，潜伏期更短，并感染可用的 BII 分离株 RCC716 和 RCC715，而 BII-V2 和 BII-V3 在我们的实验中没有表现出对后者的有效感染。全球宏基因组分析显示 Clade BI 和 BII 藻类相对丰度与其各自的病毒呈正相关。这些分布描绘了 BI/BpVs 占据了较低温度的中营养和沿海系统，而 BII/BII-Vs 占据了温度较高、盐度较高的生态系统。因此，在分子诊断支持下，我们将 Clade BII 命名为Bathycoccus calidus sp。十一月 并提出这个新物种中的分子多样性可能与我们在时间过程实验中观察到的分化的宿主病毒动力学有关。总体而言，本文观察到的Bathycoccus宿主和病毒进化枝的紧密联系的生物地理学支持物种水平的宿主特异性，感染参数具有菌株水平的变化。