Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
ISME J. 2022 Apr;16(4):972-982. doi: 10.1038/s41396-021-01143-1. Epub 2021 Nov 6.
Microbial communities in oxygen minimum zones (OMZs) are known to have significant impacts on global biogeochemical cycles, but viral influence on microbial processes in these regions are much less studied. Here we provide baseline ecological patterns using microscopy and viral metagenomics from the Eastern Tropical North Pacific (ETNP) OMZ region that enhance our understanding of viruses in these climate-critical systems. While extracellular viral abundance decreased below the oxycline, viral diversity and lytic infection frequency remained high within the OMZ, demonstrating that viral influences on microbial communities were still substantial without the detectable presence of oxygen. Viral community composition was strongly related to oxygen concentration, with viral populations in low-oxygen portions of the water column being distinct from their surface layer counterparts. However, this divergence was not accompanied by the expected differences in viral-encoded auxiliary metabolic genes (AMGs) relating to nitrogen and sulfur metabolisms that are known to be performed by microbial communities in these low-oxygen and anoxic regions. Instead, several abundant AMGs were identified in the oxycline and OMZ that may modulate host responses to low-oxygen stress. We hypothesize that this is due to selection for viral-encoded genes that influence host survivability rather than modulating host metabolic reactions within the ETNP OMZ. Together, this study shows that viruses are not only diverse throughout the water column in the ETNP, including the OMZ, but their infection of microorganisms has the potential to alter host physiological state within these biogeochemically important regions of the ocean.
海洋缺氧区（OMZ）中的微生物群落，已知对全球生物地球化学循环有着重大影响，但对这些区域中病毒对微生物过程的影响的研究却少得多。在这里，我们通过显微镜和病毒宏基因组学的方法，提供了东热带北太平洋（ETNP）OMZ 区域的基础生态学模式，从而增进了我们对这些气候关键系统中病毒的理解。尽管在氧跃层以下，细胞外病毒丰度降低，但在 OMZ 内，病毒多样性和裂解感染频率仍然很高，这表明在没有可检测到的氧气存在的情况下，病毒对微生物群落的影响仍然很大。病毒群落组成与氧浓度密切相关，水柱中低氧部分的病毒种群与表层的病毒种群截然不同。然而，这种分歧并没有伴随着与氮和硫代谢相关的预期差异，这些差异是已知的在这些低氧和缺氧区域的微生物群落中发挥作用的病毒编码辅助代谢基因（AMGs）。相反，在氧跃层和 OMZ 中鉴定出了几个丰富的 AMGs，它们可能调节宿主对低氧胁迫的反应。我们假设这是由于选择了对宿主存活有影响的病毒编码基因，而不是在 ETNP OMZ 中调节宿主的代谢反应。总的来说，这项研究表明，病毒不仅在东热带北太平洋的水柱中具有多样性，包括 OMZ，而且它们对微生物的感染有可能改变这些海洋生物地球化学重要区域中宿主的生理状态。
