Microbial ecology and environmental monitoring in micro-habitat in streams

我们开发了一种新的采样方法来收集生活在溪流鹅卵石上的微生物，以尽量减少微生物的损失。新方法收集的细菌、异养纳米鞭毛虫和纤毛虫的细胞密度往往高于传统方法。叶绿素α浓度与异养微生物和异养微生物之间的细胞密度呈显著相关，表明河流中存在活跃的微生物食物网。下一步，研究人员分析了溪流中底栖细菌的细胞密度和生产速率，以及叶绿素浓度和生物膜卵石上周围植物的初级生产，以检验初级生产是否支持这种天然水生生物膜中的细菌生产。假设细菌生长量为30%，计算出细菌产量占净初级产量的百分比为61 ~ 435%。因此，原生和外来的有机物供应很可能对淡水溪流中形成的卵石生物膜中的细菌的生产都很重要。微生物的丰度和组成易受细微环境变化的影响。因此，我们尝试使用微传感器（Unisense）检测生物膜的变化。微传感器可以测定生物膜中流速和溶解氧浓度的垂直分布。这些轮廓是不同的，取决于生物膜。这是由于生物膜中优势藻的丰度和组成所致。

We have developed a new sampling method for collecting microorganisms living on pebbles in streams to minimize the loss of microorganisms. Cell densities of bacteria, heterotrophic nanoflagellates and ciliates collected by the new method tended to be higher than those obtained by the conventional method. Significant correlations between concentration of chlorophyll α and cell densities of heterotrophic microorganisms, and among heterotrophic microorganisms suggest the presence of active microbial food webs in streams. As a next step, benthic bacterial cell densities and production rates together with chlorophyll concentration and primary production of periphyton on biofilm pebbles in a stream were analyzed to examine whether primary production supports bacterial production in this natural aquatic biofilm. Percentages of bacterial production to net primary production were calculated as 61 to 435% with the assumption of bacterial growth yield as 30%. Thus, it is likely that both autochthonous and allochthonous supplies of organic matter are important for production of bacteria in the pebble biofilms that develop in fresh water streams. Abundance and composition of microorganisms are susceptible to subtle environmental changes. Hence, we tried to detect the changes in biofilms using Microsensors (Unisense). The Microsensors could determine vertical profiles of current velocity and dissolved oxygen concentration in biofilms. These profiles were different, depending on biofilms. This is attributable to abundance and composition of dominant periphyton algae in biofilms.