PDF(Pubmed)
Abstract：
Winter is a relatively under-studied season in freshwater ecology. The paucity of wintertime surveys has led to a lack of knowledge regarding microbial community activity during the winter in Lake Erie, a North American Great Lake. Viruses shape microbial communities and regulate biogeochemical cycles by acting as top-down controls, yet very few efforts have been made to examine active virus populations during the winter in Lake Erie. Furthermore, climate change-driven declines in seasonal ice cover have been shown to influence microbial community structure, but no studies have compared viral community activity between different ice cover conditions. We surveyed surface water metatranscriptomes for viral hallmark genes as a proxy for active virus populations and compared activity metrics between ice-covered and ice-free conditions from two sampled winters. Transcriptionally active viral communities were detected in both winters, spanning diverse phylogenetic clades of putative bacteriophage (Caudoviricetes), giant viruses (Nucleocytoviricota, or NCLDV), and RNA viruses (Orthornavirae). However, viral community activity metrics revealed pronounced differences between the ice-covered and ice-free winters. Viral community composition was distinct between winters and viral hallmark gene richness was reduced in the ice-covered relative to the ice-free conditions. In addition, the observed differences in viral communities correlated with microbial community activity metrics. Overall, these findings contribute to our understanding of the viral populations that are active during the winter in Lake Erie and suggest that viral community activity may be associated with ice cover extent.IMPORTANCEAs seasonal ice cover is projected to become increasingly rare on large temperate lakes, there is a need to understand how microbial communities might respond to changing ice conditions. Although it is widely recognized that viruses impact microbial community structure and function, there is little known regarding wintertime viral activity or the relationship between viral activity and ice cover extent. Our metatranscriptomic analyses indicated that viruses were transcriptionally active in the winter surface waters of Lake Erie. These findings also expanded the known diversity of viral lineages in the Great Lakes. Notably, viral community activity metrics were significantly different between the two sampled winters. The pronounced differences we observed in active viral communities between the ice-covered and ice-free samples merit further research regarding how viral communities will function in future, potentially ice-free, freshwater systems.
摘要：
冬季是淡水生态学研究相对不足的季节。冬季调查的匮乏导致对伊利湖冬季微生物群落活动的了解不足，北美大湖。病毒通过充当自上而下的控制来塑造微生物群落并调节生物地球化学循环，然而，在伊利湖的冬季，很少有人努力检查活跃的病毒种群。此外，气候变化驱动的季节性冰盖下降已被证明会影响微生物群落结构，但是没有研究比较不同冰盖条件下的病毒群落活动。我们调查了地表水的病毒标志基因作为活跃病毒种群的代表，并比较了两个采样冬季的冰雪覆盖和无冰条件之间的活动指标。在两个冬天都检测到转录活跃的病毒群落，跨越假定的噬菌体（Cauviricetes）的不同系统发育进化枝，巨型病毒（核子细胞病毒群，或NCLDV)，和RNA病毒（Orthornavirae）。然而,病毒群落活动指标显示，冰雪覆盖的冬季和无冰的冬季之间存在明显差异。冬季之间的病毒群落组成不同，相对于无冰条件，冰覆盖的病毒标志基因丰富度降低。此外,观察到的病毒群落差异与微生物群落活性指标相关。总的来说,这些发现有助于我们了解伊利湖冬季活跃的病毒种群，并表明病毒群落活动可能与冰覆盖程度有关。重要因素预计季节性冰盖在大型温带湖泊上将变得越来越罕见，有必要了解微生物群落如何应对不断变化的冰条件。尽管人们普遍认为病毒会影响微生物群落的结构和功能，关于冬季病毒活性或病毒活性与冰覆盖程度之间的关系知之甚少。我们的元转录组学分析表明，病毒在伊利湖的冬季地表水中具有转录活性。这些发现还扩大了大湖区病毒谱系的已知多样性。值得注意的是,两个采样冬季之间的病毒群落活动指标显着不同。我们在冰雪覆盖和无冰样本之间的活跃病毒群落中观察到的明显差异值得进一步研究，以了解病毒群落在未来如何发挥作用。潜在的无冰，淡水系统。
