Rønn Regin, McCaig Allison E, Griffiths Bryan S, Prosser James I
Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, United Kingdom.
Appl Environ Microbiol. 2002 Dec;68(12):6094-105. doi: 10.1128/AEM.68.12.6094-6105.2002.
The influence of grazing by a mixed assemblage of soil protozoa (seven flagellates and one amoeba) on bacterial community structure was studied in soil microcosms amended with a particulate resource (sterile wheat roots) or a soluble resource (a solution of various organic compounds). Sterilized soil was reinoculated with mixed soil bacteria (obtained by filtering and dilution) or with bacteria and protozoa. Denaturing gradient gel electrophoresis (DGGE) of PCR amplifications of 16S rRNA gene fragments, as well as community level physiological profiling (Biolog plates), suggested that the mixed protozoan community had significant effects on the bacterial community structure. Excising and sequencing of bands from the DGGE gels indicated that high-G+C gram-positive bacteria closely related to Arthrobacter spp. were favored by grazing, whereas the excised bands that decreased in intensity were related to gram-negative bacteria. The percentages of intensity found in bands related to high G+C gram positives increased from 4.5 and 12.6% in the ungrazed microcosms amended with roots and nutrient solution, respectively, to 19.3 and 32.9% in the grazed microcosms. Protozoa reduced the average bacterial cell size in microcosms amended with nutrient solution but not in the treatment amended with roots. Hence, size-selective feeding may explain some but not all of the changes in bacterial community structure. Five different protozoan isolates (Acanthamoeba sp., two species of Cercomonas, Thaumatomonas sp., and Spumella sp.) had different effects on the bacterial communities. This suggests that the composition of protozoan communities is important for the effect of protozoan grazing on bacterial communities.
在添加了颗粒状资源（无菌小麦根）或可溶性资源（各种有机化合物溶液）的土壤微观系统中，研究了由七种鞭毛虫和一种变形虫组成的混合土壤原生动物群落的放牧对细菌群落结构的影响。用混合土壤细菌（通过过滤和稀释获得）或细菌与原生动物对灭菌土壤进行重新接种。对16S rRNA基因片段进行PCR扩增后的变性梯度凝胶电泳（DGGE）以及群落水平生理特征分析（Biolog平板）表明，混合原生动物群落对细菌群落结构有显著影响。从DGGE凝胶中切下条带并测序表明，与节杆菌属密切相关的高G+C革兰氏阳性菌在放牧时更受青睐，而强度降低的切下条带与革兰氏阴性菌有关。与高G+C革兰氏阳性菌相关的条带强度百分比，在添加根和营养液的未放牧微观系统中分别从4.5%和12.6%增加到放牧微观系统中的19.3%和32.9%。原生动物在添加营养液的微观系统中减小了细菌平均细胞大小，但在添加根的处理中没有。因此，大小选择性摄食可能解释了细菌群落结构变化的部分而非全部原因。五种不同的原生动物分离株（棘阿米巴属、两种圆壳虫属、奇异滴虫属和泡沫虫属）对细菌群落有不同影响。这表明原生动物群落的组成对于原生动物放牧对细菌群落的影响很重要。
