Laboratoire Microorganismes, Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, Aubière, France.
Appl Environ Microbiol. 2011 Aug 15;77(16):5610-8. doi: 10.1128/AEM.01370-10. Epub 2011 Jul 1.
We explored the abundance and infection rates of viruses on a time series scale in the euphotic zone of the humic mesotrophic Lake Vassivière (Massif Central, France) and compared them to nonhumic lakes of contrasting trophy (i.e., the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat) located in the same geographical region and sampled during the same period. In Lake Vassivière, the abundances of virus-like particles (range, 1.7 × 10(10) to 2.6 × 10(10) liter(-1)) were significantly (P < 0.001) lower than in Lakes Pavin and Aydat. The percentage of virus-infected prokaryotic cells (mean, 18.0%) was significantly higher (P < 0.001) in Vassivière than in Pavin (mean, 11.5%) and Aydat (mean, 9.7%). In Vassivière, the abundance of prokaryotes was a good predictor (r = 0.78, P < 0.001) of the number of virus-like particles, while the potential grazing rate from heterotrophic nanoflagellates was positively correlated to the viral infection rate (r = 0.75, P < 0.001; n = 20), indicating the prevalence of cycling interactions among viruses, prokaryotes, and grazers, which is in agreement with past experiments. The absence of correlation between chlorophyll a concentrations (Chl) and viral parameters suggested that the resources for the lytic activity of viruses in Vassivière were mainly under allochthonous control, through host activity. Indeed, compilation of data obtained from several nonhumic lakes in the French Massif Central revealed that Chl was positively correlated to the abundance of virus-like particles at concentrations above 0.5 μg Chl liter(-1) and negatively at concentrations below 0.5 μg Chl liter(-1), suggesting that phytoplankton-derived resources could force prokaryotic growth to attain a certain threshold level when the host availability is sufficient to boost the proliferation of viruses. Therefore, based on the high level of lytic infection rates in Lake Vassivière, we conclude that viruses are key agents for prokaryotic mortality and could influence the food web dynamics in humic lakes, which may ultimately depend on the internal cycling of resources and, perhaps, mainly on the allochthonous inputs and the associated humic substances.
我们在富营养的中营养 Vassivière 湖（法国中央高原）的光区按时间序列尺度研究了病毒的丰度和感染率，并将其与位于同一地理区域且在同一时期采样的非富营养化湖泊（即寡营养的 Pavin 湖和富营养的 Aydat 湖）进行了比较。在 Vassivière 湖中，病毒样颗粒的丰度（范围为 1.7×10(10)到 2.6×10(10)升(-1))明显低于 Pavin 和 Aydat 湖。（平均为 18.0%）感染病毒的原核细胞的百分比明显高于 Pavin（平均为 11.5%）和 Aydat（平均为 9.7%）。在 Vassivière 湖中，原核生物的丰度是病毒样颗粒数量的一个很好的预测因子（r = 0.78，P < 0.001），而异养微型鞭毛虫的潜在摄食率与病毒感染率呈正相关（r = 0.75，P < 0.001；n = 20），表明病毒、原核生物和食草动物之间的循环相互作用普遍存在，这与过去的实验结果一致。叶绿素 a 浓度（Chl）与病毒参数之间没有相关性表明，在 Vassivière 湖中，病毒的裂解活性的资源主要受异源控制，通过宿主活动。事实上，从法国中央高原的几个非富营养化湖泊中收集的数据汇编表明，Chl 与病毒样颗粒的丰度呈正相关，当浓度高于 0.5μg Chl 升(-1)时，与浓度低于 0.5μg Chl 升(-1)时呈负相关，这表明浮游植物衍生的资源可以迫使原核生物生长达到一定的阈值水平，当宿主可用性足以促进病毒的增殖时。因此，基于 Vassivière 湖中高的裂解感染率，我们得出结论，病毒是原核生物死亡率的关键因素，并可能影响富营养化湖泊的食物网动态，这可能最终取决于资源的内部循环，也许主要取决于异源输入和相关的腐殖质。
