bioreactor sludge metatranscriptome Raw sequence reads. bioreactor sludge metagenome

We recently isolated and characterized a predatory Bdellovibrio bacteriovorus strain from activated sludge (Ulu Pandan Water Reclamation Plant, Singapore), and this strain, B. bacteriovorus UP was able to prey upon a broad spectrum of bacterial isolates from the activated sludge when grown as planktonic cells or as biofilms. Here, we have tested the effect of Bdellovibrio predation on floccular and granular sludge to determine if the spatial organization, loosely or tightly aggregated communities, was protective from predation. The effect of predation was assessed using a combination of biomass quantification, cellular activity measurement and microscopic image analysis to determine community viability. Additionally, changes in the microbial communities due to predation by B. bacteriovorus UP were analyzed through total RNA sequencing. Predation led to a significant reduction in microbial activity and total biomass for both floccular and granular sludge communities. Predation was also associated with significant changes in the microbial community composition in both communities, with >90% of the community members reduced in relative abundance after 24 h. Of those community members, the dominant organisms, such as Proteobacteria and Bacteroidetes, were the most affected phylotypes. This suggests that predatory bacteria, which display indiscriminant feeding, could significantly shift the species composition and thus, may disturb the operational performance of wastewater treatment systems.

本研究团队近期从新加坡乌鲁班丹净水回收厂（Ulu Pandan Water Reclamation Plant）的活性污泥中分离并鉴定了一株捕食性蛭弧菌（Bdellovibrio bacteriovorus），命名为B. bacteriovorus UP。该菌株在以浮游细胞或生物膜形式生长时，可捕食从该活性污泥中分离得到的多种细菌菌株。本研究通过探究蛭弧菌捕食作用对絮状污泥与颗粒污泥的影响，旨在明确松散聚集或紧密聚集的群落空间结构是否能够抵御捕食。研究采用生物量定量、细胞活性检测与显微图像分析相结合的方式评估捕食效果，以测定群落生存活力。此外，本研究通过总RNA测序（total RNA sequencing）分析了B. bacteriovorus UP捕食作用下微生物群落的组成变化。实验结果显示，捕食作用可显著降低絮状与颗粒污泥群落的微生物活性与总生物量。两类污泥群落的微生物群落组成均发生显著改变，培养24小时后，超过90%的群落成员相对丰度出现下降。其中，变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）等优势菌群受影响最为显著。该结果表明，无选择性摄食的捕食性细菌可显著改变群落物种组成，进而可能干扰污水处理系统的运行效能。