Department of Stratified Lakes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Alte Fischerhuette 2, 16775 Stechlin, Germany.
Microb Ecol. 2010 Aug;60(2):462-75. doi: 10.1007/s00248-010-9639-0. Epub 2010 Mar 3.
In many limnetic systems, the input of allochthonous organic matter, e.g., leaf litter, is a substantial source of dissolved organic carbon (DOC) for pelagic bacteria, especially in fall and winter when autochthonous DOC production is low. However, relatively little is known about community changes of pelagic lake bacteria due to leaf litter input which includes both the release of leaf leachates and microorganisms from the leaf litter into the surrounding water. Therefore, we have experimentally studied the effects of different types of leaf litter (Betula pendula, Fagus silvatica, and Pinus silvestris) on the pelagic bacterial community composition by adding leaves to different treatments of epilimnic water samples (unfiltered, 0.2 µm and 5.0 µm-pre-filtered) from humic Lake Grosse Fuchskuhle (Northeastern Germany). The addition of leaf litter led to a significant increase in DOC concentration in lake water, and each leaf litter type produced significantly different amounts of DOC (p = <0.001) as well as of specific DOC fractions (p = <0.001), except of polysaccharides. DGGE banding patterns varied over time, between types of leaf litter, and among treatments. Bacteria belonging to known bacterial phylotypes in the southwest basin of Lake Grosse Fuchskuhle were frequently found and even persisted after leaf litter additions. Upon leaf litter addition, α-proteobacteria (Azospirillum, Novosphingobium, and Sphingopyxis) as well as β-proteobacteria (Curvibacter and Polynucleobacter) were enriched. Our results indicate that supply of leaf litter DOM shifted the bacterial community in the surrounding water towards specific phylotypes including species capable of assimilating the more recalcitrant DOC pools. Statistical analyses, however, show that DGGE banding patterns are not only affected by DOC pools but also by treatment. This indicates that biological factors such as source community and grazing may be also important for shifts in bacterial community structure following leaf litter input into different lakes.
在许多湖泊系统中，异源有机物质（例如落叶）的输入是浮游细菌溶解有机碳（DOC）的重要来源，尤其是在秋季和冬季，此时自生 DOC 产量较低。然而，由于落叶输入包括落叶浸出物和落叶中的微生物释放到周围水中，因此，对于浮游湖细菌群落的变化，人们知之甚少。因此，我们通过将落叶添加到富营养化的格罗斯富克斯库勒湖（德国东北部）的不同处理的表水水样（未过滤，0.2 µm 和 5.0 µm 预过滤器）中，实验研究了不同类型的落叶（桦树，山毛榉和松树）对浮游细菌群落组成的影响。落叶的添加导致湖水 DOC 浓度显着增加，并且每种落叶类型产生的 DOC 量明显不同（p <0.001）以及特定的 DOC 分数（p <0.001），除了多糖。DGGE 带型随时间，落叶类型和处理方式而变化。属于格罗斯富克斯库勒湖西南盆地中已知细菌类群的细菌经常被发现，甚至在落叶添加后仍然存在。落叶添加后，α-变形菌（Azospirillum，Novosphingobium 和 Sphingopyxis）以及β-变形菌（Curvibacter 和 Polynucleobacter）得到了富集。我们的结果表明，落叶 DOM 的供应使周围水中的细菌群落向包括能够同化更难分解的 DOC 库的特定类群转移。但是，统计分析表明，DGGE 带型不仅受 DOC 库的影响，还受处理的影响。这表明，生物因素（例如源群落和放牧）对于落叶输入到不同湖泊后细菌群落结构的变化也可能很重要。
