Salcher Michaela M, Hofer Julia, Hornák Karel, Jezbera Jan, Sonntag Bettina, Vrba Jaroslav, Simek Karel, Posch Thomas
Department of Limnology, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
FEMS Microbiol Ecol. 2007 Apr;60(1):40-50. doi: 10.1111/j.1574-6941.2006.00274.x. Epub 2007 Jan 24.
We simultaneously studied the impact of top-down (protistan grazing) and bottom-up (phosphorus availability) factors on the numbers and biomasses of bacteria from various phylogenetic lineages, and on their growth and activity parameters in the oligo-mesotrophic Piburger See, Austria. Enhanced grazing resulted in decreased proportions of bacteria with high nucleic acid content (high-NA bacteria) and lower detection rates by FISH. There was a change in the composition of the bacterial assemblage, whereby Betaproteobacteria were heavily grazed while Alphaproteobacteria and Cytophaga-Flavobacterium-Bacteroides were less affected by predators. Changes in bacterial assemblage composition were also apparent in the treatments enriched with phosphorus, and even more pronounced in the incubations in dialysis tubes (allowing relatively free nutrient exchange). Here, Betaproteobacteria became dominant and appeared to act as successful opportunistic competitors for nutrients. In contrast, Actinobacteria did not respond to surplus phosphorus by population growth, and, moreover, maintained their small size, which resulted in a very low biomass contribution. In addition, significant relationships between high-NA bacteria and several bacterial phylogenetic clades were found, indicating an enhanced activity status. By combining several single-cell methods, new insight is gained into the competitive abilities of freshwater bacteria from a variety of phylogenetic lineages under contrasting sets of bottom-up and top-down constraints.
我们同时研究了自上而下（原生生物捕食）和自下而上（磷有效性）因素对奥地利贫-中营养的皮布尔格湖不同系统发育谱系细菌的数量和生物量，以及它们的生长和活性参数的影响。捕食增强导致高核酸含量细菌（高NA细菌）比例降低，荧光原位杂交（FISH）检测率降低。细菌群落组成发生了变化，其中β-变形菌被大量捕食，而α-变形菌和噬纤维菌-黄杆菌-拟杆菌受捕食者影响较小。在添加磷的处理中，细菌群落组成的变化也很明显，在透析管培养中（允许相对自由的营养物质交换）更为显著。在这里，β-变形菌占主导地位，似乎是成功的营养物质机会主义竞争者。相比之下，放线菌不会因磷过剩而通过种群增长做出反应，而且，它们保持较小的尺寸，这导致其生物量贡献非常低。此外，还发现高NA细菌与几个细菌系统发育分支之间存在显著关系，表明其活性状态增强。通过结合多种单细胞方法，我们对不同系统发育谱系的淡水细菌在自下而上和自上而下的不同限制条件下的竞争能力有了新的认识。
