Centre for Marine Bio-Innovation, University of New South Wales, Sydney, NSW 2052, Australia.
Appl Environ Microbiol. 2010 Apr;76(7):2203-11. doi: 10.1128/AEM.02777-09. Epub 2010 Feb 5.
It is well understood that protozoa play a major role in controlling bacterial biomass and regulating nutrient cycling in the environment. Little is known, however, about the movement of carbon from specific reduced substrates, through functional groups of bacteria, to particular clades of protozoa. In this study we first identified the active protozoan phylotypes present in activated sludge, via the construction of an rRNA-derived eukaryote clone library. Most of the sequences identified belonged to ciliates of the subclass Peritrichia and amoebae, confirming the dominance of surface-associated protozoa in the activated sludge environment. We then demonstrated that (13)C-labeled protozoan RNA can be retrieved from activated sludge amended with (13)C-labeled protozoa or (13)C-labeled Escherichia coli cells by using an RNA stable isotope probing (RNA-SIP) approach. Finally, we used RNA-SIP to track carbon from bicarbonate and acetate into protozoa under ammonia-oxidizing and denitrifying conditions, respectively. RNA-SIP analysis revealed that the peritrich ciliate Epistylis galea dominated the acquisition of carbon from bacteria with access to CO(2) under ammonia-oxidizing conditions, while there was no evidence of specific grazing on acetate consumers under denitrifying conditions.
众所周知，原生动物在控制细菌生物量和调节环境中营养循环方面起着重要作用。然而，对于特定还原底物的碳从特定细菌功能群到特定原生动物类群的转移过程知之甚少。在这项研究中，我们首先通过构建 rRNA 衍生的真核生物克隆文库，鉴定了活性污泥中存在的活跃原生动物的分类群。大多数鉴定的序列属于纤毛亚纲的缘毛目和变形虫，证实了表面相关原生动物在活性污泥环境中的优势地位。然后，我们通过使用 RNA 稳定同位素探测（RNA-SIP）方法，证明了可以从添加了（13）C 标记原生动物或（13）C 标记大肠杆菌细胞的活性污泥中回收（13）C 标记的原生动物 RNA。最后，我们使用 RNA-SIP 分别在氨氧化和反硝化条件下，追踪碳酸氢盐和乙酸盐中的碳进入原生动物。RNA-SIP 分析表明，在氨氧化条件下，当可以利用 CO2 时，缘毛目纤毛虫 Epistylis galea 占主导地位，从细菌中获取碳，而在反硝化条件下，没有证据表明有特定的对乙酸消费者的捕食。
