Hahn M W, Höfle M G
Microbial Ecology Group, GBF-National Research Center of Biotechnology, D-38124 Braunschweig, Germany.
Appl Environ Microbiol. 1999 Nov;65(11):4863-72. doi: 10.1128/AEM.65.11.4863-4872.1999.
The influence of grazing by the bacterivorous nanoflagellate Ochromonas sp. strain DS on the taxonomic and morphological structures of a complex bacterial community was studied in one-stage chemostat experiments. A bacterial community, consisting of at least 30 different strains, was fed with a complex carbon source under conditions of low growth rate (0.5 day(-1) when nongrazed) and low substrate concentration (9 mg liter(-1)). Before and after the introduction of the predator, the bacterial community composition was studied by in situ techniques (immunofluorescence microscopy and fluorescent in situ hybridization), as well as by cultivation on agar media. The cell sizes of nonspecifically stained and immunofluorescently labeled bacteria were measured by image analysis. Grazing by the flagellate caused a bidirectional change in the morphological structure of the community. Medium-size bacterial cells, which dominated the nongrazed community, were largely replaced by smaller cells, as well as by cells contained in large multicellular flocs. Cell morphological changes were combined with community taxonomic changes. After introduction of the flagellate, the dominating strains with medium-size cells were largely replaced by single-celled strains with smaller cells on the one hand and, on the other hand, by Pseudomonas sp. strain MWH1, which formed the large, floc-like forms. We assume that size-selective grazing was the major force controlling both the morphological and the taxonomic structures of the model community.
在单阶段恒化器实验中，研究了食细菌纳米鞭毛虫赭纤虫属（Ochromonas sp.）菌株DS的捕食对复杂细菌群落的分类和形态结构的影响。在低生长速率（未被捕食时为0.5天⁻¹）和低底物浓度（9毫克/升）条件下，用复杂碳源喂养一个由至少30种不同菌株组成的细菌群落。在引入捕食者之前和之后，通过原位技术（免疫荧光显微镜和荧光原位杂交）以及在琼脂培养基上培养来研究细菌群落组成。通过图像分析测量非特异性染色和免疫荧光标记细菌的细胞大小。鞭毛虫的捕食导致群落形态结构发生双向变化。在未被捕食的群落中占主导地位的中等大小细菌细胞，在很大程度上被较小的细胞以及包含在大型多细胞絮凝物中的细胞所取代。细胞形态变化与群落分类变化相结合。引入鞭毛虫后，一方面，具有中等大小细胞的主导菌株在很大程度上被具有较小细胞的单细胞菌株所取代，另一方面，被形成大型絮状形态的假单胞菌属菌株MWH1所取代。我们认为大小选择性捕食是控制模型群落形态和分类结构的主要力量。
