INRA, UMR CARRTEL, 75 avenue de Corzent, 74200, Thonon-les-Bains, France.
Microb Ecol. 2011 May;61(4):941-54. doi: 10.1007/s00248-010-9767-6. Epub 2010 Nov 17.
Despite the considerable attention that has been paid to bacterioplankton over recent decades, the dynamic of aquatic bacterial community structure is still poorly understood, and long-term studies are particularly lacking. Moreover, how the environment governs diversity patterns remains a key issue in aquatic microbial ecology. In this study, we used denaturing gradient gel electrophoresis of PCR-amplified partial 16S rRNA gene fragments and multivariable statistical approaches to explore the patterns of change in the free-living bacterial community in the mesotrophic and mono-meromictic Lake Bourget (France). A monthly sampling was conducted over two consecutive years (2007 and 2008) and at two different depths characterizing the epi- and hypolimnion of the lake (2 and 50 m, respectively). Temporal shifts in the bacterial community structure followed different patterns according to depth, and no seasonal reproducibility was recorded from 1 year to the next. Our results showed that the bacterial community structure displayed lower diversity at 2 m (22 bands) compared to 50 m (32 bands) and that bacterial community structure dynamics followed dissimilar trends between the two depths. At 2 m, five shifts in the bacterial community structure occurred, with the temporal scale varying between 2 and 8 months whereas, at 50 m, four shifts in the bacterial community structure took place at 50 m, with the temporal scale fluctuating between 3 and 13 months. More than 60% of the bacterial community structure variance was explained by seven variables at 2 m against eight at 50 m. Nutrients (PO(4)-P, NH(4)-N and NO(3)-N) and temperature were responsible for 49.6% of the variance at 2 m whereas these nutrients, with dissolved oxygen and chlorophyll a accounting for 59.6% of the variance at 50 m. Grazing by ciliates played also a critical role on the bacterial community structure at both depths. Our results suggest that the free-living bacterial community structure in the epi- and hypolimnion of Lake Bourget is mainly driven by combined, but differently weighted, top-down and bottom-up factors at 2 and 50 m.
尽管近几十年来人们对浮游细菌高度关注，但水生细菌群落结构的动态仍然知之甚少，特别是缺乏长期研究。此外，环境如何控制多样性格局仍然是水生微生物生态学的一个关键问题。在这项研究中，我们使用 PCR 扩增的部分 16S rRNA 基因片段的变性梯度凝胶电泳和多变量统计方法来探索法国中营养和单分层的 Bourget 湖浮游细菌群落的变化模式。在两年（2007 年和 2008 年）的连续时间内，每月在湖的表水层和下水层（分别为 2 和 50 米）进行采样。根据深度，细菌群落结构的时间变化遵循不同的模式，并且第二年与第一年之间没有记录到季节性重现性。我们的结果表明，与 50 m 相比，细菌群落结构在 2 m 处的多样性较低（22 条带），并且细菌群落结构动态在两个深度之间呈现出不同的趋势。在 2 m 处，发生了五次细菌群落结构的变化，时间尺度在 2 到 8 个月之间，而在 50 m 处，细菌群落结构发生了四次变化，时间尺度在 3 到 13 个月之间波动。在 2 m 处，有 7 个变量解释了超过 60％的细菌群落结构方差，而在 50 m 处有 8 个变量。在 2 m 处，营养物质（PO4-P、NH4-N 和 NO3-N）和温度占方差的 49.6％，而在 50 m 处，这些营养物质、溶解氧和叶绿素 a 占方差的 59.6％。纤毛虫的摄食在上下水层的细菌群落结构中也起着至关重要的作用。我们的结果表明，在 Bourget 湖的表水层和下水层中，自由生活的细菌群落结构主要受到 2 和 50 m 处的自上而下和自下而上因素的共同作用，但权重不同。
