Pernthaler J, Posch T, Simek K, Vrba J, Pernthaler A, Glöckner F O, Nübel U, Psenner R, Amann R
Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, D-28359 Bremen, Germany.
Appl Environ Microbiol. 2001 May;67(5):2145-55. doi: 10.1128/AEM.67.5.2145-2155.2001.
We investigated whether individual populations of freshwater bacteria in mixed experimental communities may exhibit specific responses to the presence of different bacterivorous protists. In two successive experiments, a two-stage continuous cultivation system was inoculated with nonaxenic batch cultures of the cryptophyte Cryptomonas sp. Algal exudates provided the sole source of organic carbon for growth of the accompanying microflora. The dynamics of several 16S rRNA-defined bacterial populations were followed in the experimental communities. Although the composition and stability of the two microbial communities differed, numerous members of the first assemblage could again be detected during the second experiment. The introduction of a size-selectively feeding mixotrophic nanoflagellate (Ochromonas sp.) always resulted in an immediate bloom of a single phylotype population of members of the class Actinobacteria (Ac1). These bacteria were phylogenetically affiliated with an uncultured lineage of gram-positive bacteria that have been found in freshwater habitats only. The Ac1 cells were close to the average size of freshwater bacterioplankton and significantly smaller than any of the other experimental community members. In contrast, no increase of the Ac1 population was observed in vessels exposed to the bacterivorous ciliate Cyclidium glaucoma. However, when the Ochromonas sp. was added after the establishment of C. glaucoma, the proportion of population Ac1 within the microbial community rapidly increased. Populations of a beta proteobacterial phylotype related to an Aquabacterium sp. decreased relative to the total bacterial communities following the addition of either predator, albeit to different extents. The community structure of pelagic microbial assemblages can therefore be influenced by the taxonomic composition of the predator community.
我们研究了混合实验群落中的淡水细菌个体群体是否会对不同食细菌原生生物的存在表现出特定反应。在两个连续的实验中，一个两阶段连续培养系统接种了隐藻Cryptomonas sp.的非无菌分批培养物。藻类分泌物为伴随的微生物群落生长提供了唯一的有机碳源。在实验群落中追踪了几个由16S rRNA定义的细菌群体的动态。尽管两个微生物群落的组成和稳定性不同，但在第二个实验中仍能再次检测到第一个组合中的许多成员。引入一种大小选择性摄食的混合营养型纳米鞭毛虫（赭鞭虫属）总是导致放线菌纲（Ac1）成员的单个系统发育型群体立即大量繁殖。这些细菌在系统发育上与仅在淡水生境中发现的未培养革兰氏阳性细菌谱系有关。Ac1细胞接近淡水浮游细菌的平均大小，且明显小于任何其他实验群落成员。相比之下，在暴露于食细菌纤毛虫青光眼睫滴虫的容器中未观察到Ac1群体的增加。然而，当在青光眼睫滴虫建立后添加赭鞭虫属时，微生物群落中Ac1群体的比例迅速增加。添加任何一种捕食者后，与水生杆菌属相关的β-变形菌系统发育型群体相对于总细菌群落均有所减少，尽管程度不同。因此，浮游微生物组合的群落结构可能会受到捕食者群落分类组成的影响。
