Helmholtz Centre for Environmental Research-UFZ, Department River Ecology, Magdeburg, Germany.
Appl Environ Microbiol. 2012 Mar;78(6):2013-24. doi: 10.1128/AEM.06517-11. Epub 2012 Jan 13.
The effects of protozoa (heterotrophic flagellates and ciliates) on the morphology and community composition of bacterial biofilms were tested under natural background conditions by applying size fractionation in a river bypass system. Confocal laser scanning microscopy (CLSM) was used to monitor the morphological structure of the biofilm, and fingerprinting methods (single-stranded conformation polymorphism [SSCP] and denaturing gradient gel electrophoresis [DGGE]) were utilized to assess changes in bacterial community composition. Season and internal population dynamics had a greater influence on the bacterial biofilm than the presence of protozoa. Within this general framework, bacterial area coverage and microcolony abundance were nevertheless enhanced by the presence of ciliates (but not by the presence of flagellates). We also found that the richness of bacterial operational taxonomic units was much higher in planktonic founder communities than in the ones establishing the biofilm. Within the first 2 h of colonization of an empty substrate by bacteria, the presence of flagellates additionally altered their biofilm community composition. As the biofilms matured, the number of bacterial operational taxonomic units increased when flagellates were present in high abundances. The additional presence of ciliates tended to at first reduce (days 2 to 7) and later increase (days 14 to 29) bacterial operational taxonomic unit richness. Altogether, the response of the bacterial community to protozoan grazing pressure was small compared to that reported in planktonic studies, but our findings contradict the assumption of a general grazing resistance of bacterial biofilms toward protozoa.
采用河流旁路系统中的分级分离法，在自然背景条件下，研究原生动物（异养鞭毛虫和纤毛虫）对细菌生物膜形态和群落组成的影响。共聚焦激光扫描显微镜（CLSM）用于监测生物膜的形态结构，指纹图谱方法（单链构象多态性[SSCP]和变性梯度凝胶电泳[DGGE]）用于评估细菌群落组成的变化。季节和内部种群动态对细菌生物膜的影响大于原生动物的存在。在这个总体框架内，纤毛虫的存在（而不是鞭毛虫的存在）增强了细菌的面积覆盖率和微菌落丰度。我们还发现，浮游生物起始群落中的细菌操作分类单元的丰富度远高于生物膜形成群落。在细菌对空底物进行 2 小时的定殖过程中，鞭毛虫的存在还改变了它们的生物膜群落组成。随着生物膜的成熟，当鞭毛虫大量存在时，细菌操作分类单元的数量增加。纤毛虫的额外存在最初倾向于减少（第 2 天至第 7 天），然后增加（第 14 天至第 29 天）细菌操作分类单元的丰富度。总的来说，与浮游研究中报告的结果相比，细菌群落对原生动物摄食压力的反应较小，但我们的发现与细菌生物膜对原生动物普遍具有抗食性的假设相矛盾。
