Liu Jie, Zhao Renxin, Zhang Jiayu, Zhang Guijuan, Yu Ke, Li Xiaoyan, Li Bing
Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Graduate School at Shenzhen, Tsinghua University, Shenzhen, China.
School of Environment and Energy, Shenzhen Graduate School, Peking University, Shenzhen, China.
Front Microbiol. 2018 Dec 5;9:2922. doi: 10.3389/fmicb.2018.02922. eCollection 2018.
Ultramicrobacteria (UMB) are omnipresent and numerically dominate in freshwater, as microbes can present in drinking water systems, however, the UMB communities that occur and their removal behaviors remain poorly characterized in drinking water treatment plants (DWTPs). To gain insights into these issues, we profiled bacterial cell density, community structure and functions of UMB and their counterpart large bacteria (LB) using flow cytometry and filtration paired with 16S rRNA gene high-throughput sequencing in a full-scale DWTP. Contrary to the reduction of bacterial density and diversity, the proportion of UMB in the total bacteria community increased as the drinking water treatment process progressed, and biological activated carbon facilitated bacterial growth. Moreover, UMB were less diverse than LB, and their community structure and predicted functions were significantly different. In the DWTP, UMB indicator taxa were mainly affiliated with α/β/γ-, and . In particular, the exclusive clustering of UMB at the phylum level, e.g., , and , confirmed the fact that the ultra-small size of UMB is a naturally and evolutionarily conserved trait. Additionally, the streamlined genome could be connected to UMB, such as candidate phyla radiation (CPR) bacteria, following a symbiotic or parasitic lifestyle, which then leads to the observed high connectedness, i.e., non-random intra-taxa co-occurrence patterns within UMB. Functional prediction analysis revealed that environmental information processing and DNA replication and repair likely contribute to the higher resistance of UMB to drinking water treatment processes in comparison to LB. Overall, the study provides valuable insights into the occurrence and fate of UMB regarding community structure, phylogenetic characteristics and potential functions in a full-scale DWTP, and it is a useful reference for beneficial manipulation of the drinking water microbiome.
超微细菌（UMB）无处不在，在淡水中数量占主导地位，因为微生物可能存在于饮用水系统中。然而，在饮用水处理厂（DWTPs）中，UMB群落的存在情况及其去除行为仍缺乏充分的特征描述。为了深入了解这些问题，我们在一座全规模DWTP中，使用流式细胞术和过滤技术结合16S rRNA基因高通量测序，对UMB及其对应的大细菌（LB）的细菌细胞密度、群落结构和功能进行了分析。与细菌密度和多样性的降低相反，随着饮用水处理过程的推进，UMB在总细菌群落中的比例增加，并且生物活性炭促进了细菌生长。此外，UMB的多样性低于LB，它们的群落结构和预测功能也存在显著差异。在DWTP中，UMB指示分类群主要隶属于α/β/γ-和。特别是，UMB在门水平上的独特聚类，例如，和，证实了UMB的超小尺寸是一种自然且在进化上保守的特征这一事实。此外，精简的基因组可能与UMB相关，例如候选门辐射（CPR）细菌，它们遵循共生或寄生的生活方式，进而导致观察到的高连通性，即UMB内部非随机的类群内共现模式。功能预测分析表明，与LB相比，环境信息处理以及DNA复制和修复可能有助于UMB对饮用水处理过程具有更高的抗性。总体而言，该研究为全规模DWTP中UMB在群落结构、系统发育特征和潜在功能方面的存在情况及归宿提供了有价值的见解，并且对于有益地操控饮用水微生物群落是一个有用的参考。
