Morphological and compositional shifts in an experimental bacterial community influenced by protists with contrasting feeding modes
Morphological and compositional shifts in an experimental bacterial community influenced by protists with contrasting feeding modes
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受原生生物影响的实验细菌群落的形态和组成变化
DOI：
10.1128/aem.63.2.587-595.1997
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发表时间：
1997
影响因子：
4.4
通讯作者：
R. Psenner
中科院分区：
文献类型：
--
作者：
K. Šimek;J. Vrba;J. Pernthaler;T. Posch;P. Hartman;J. Nedoma;R. Psenner
在两阶段连续流系统中，研究了不同原生动物摄食方式对混合菌群形态和分类结构的影响。两个平行操作的三个第二阶段接种的食菌鞭毛虫，Bodo saltans，和食藻纤毛虫，叉尾丝藻，分别。第三艘船作为对照。在两个实验中，藻类和细菌种群的增长率和密度典型的富营养化沃茨，我们比较了准稳态条件下的原生动物接种后的瞬态阶段的细菌，藻类和原生动物的群落变化。采用荧光寡核苷酸探针原位杂交和培养法对细菌群落组成进行了初步分析。最初，所有培养容器的细胞大小分布和群落结构显示出相似的模式，具有来自变形菌门（（β）-变形菌门）的β亚门的1-至2.5-（μ）m长的杆的优势。接种纤毛虫增加细菌生长在这个基板控制的变种，似乎通过回收的营养物质和基板上放牧藻类释放，但没有任何可检测到的影响细菌组合物的组成。相反，接种噬菌体B。saltans，导致（β）-变形菌门的比例降低。此外，一部分组合（<总细菌数量的4%）产生了大的耐放牧的线状细胞。作为B。Saltans只摄取<3 μ m的细胞，这种策略产生了70%的总细菌生物量免于被吃掉的避难所。在这种变体中，严重捕食的另一个后果是向（α）-变形菌门的数量优势转变。细菌群落的严重放牧区段的增强的生理状态导致CFU的比例（平均，总细菌计数的88%）比其他变体高得多，其中CFU占（symbbl）30%。然而，观察到细菌群落的显著培养依赖性转变朝向（γ）-变形菌和噬纤维菌/黄杆菌组的成员，这表明基于培养的方法和寡核苷酸探测之间的相当差的一致性。
In a two-stage continuous-flow system, we studied the impacts of different protozoan feeding modes on the morphology and taxonomic structure of mixed bacterial consortia, which were utilizing organic carbon released by a pure culture of a Rhodomonas sp. grown on inorganic medium in the first stage of the system. Two of three second stages operated in parallel were inoculated by a bacterivorous flagellate, Bodo saltans, and an algivorous ciliate, Urotricha furcata, respectively. The third vessel served as a control. In two experiments, where algal and bacterial populations grew at rates and densities typical for eutrophic waters, we compared community changes of bacteria, algae, and protozoa under quasi-steady-state conditions and during the transient stage after the protozoan inoculation. In situ hybridization with fluorescent oligonucleotide probes and cultivation-based approaches were used to tentatively analyze the bacterial community composition. Initially the cell size distribution and community structure of all cultivation vessels showed similar patterns, with a dominance of 1- to 2.5-(mu)m-long rods from the beta subdivision of the phylum Proteobacteria ((beta)-Proteobacteria). Inoculation with the ciliate increased bacterial growth in this substrate-controlled variant, seemingly via a recycling of nutrients and substrate released by grazing on algae, but without any detectable effect on the composition of bacterial assemblage. In contrast, an inoculation with the bacterivore, B. saltans, resulted in a decreased proportion of the (beta)-Proteobacteria. One part of the assemblage (<4% of total bacterial numbers), moreover, produced large grazing-resistant threadlike cells. As B. saltans ingested only cells of <3 (mu)m, this strategy yielded a refuge for (symbl)70% of total bacterial biomass from being grazed. Another consequence of the heavy predation in this variant was a shift to the numerical dominance of the (alpha)-Proteobacteria. The enhanced physiological status of the heavily grazed-upon segment of bacterial community resulted in a much higher proportion of CFU (mean, 88% of total bacterial counts) than with other variants, where CFU accounted for (symbl)30%. However, significant cultivation-dependent shifts of the bacterial community were observed toward (gamma)-Proteobacteria and members of the Cytophaga/Flavobacterium group, which demonstrated the rather poor agreement between cultivation-based approaches and oligonucleotide probing.