Abstract：
Biofilms on the inner surface of a drinking water distribution system (DWDS) affect water quality and stability. Understanding the niche differentiation of biofilm microbial communities is necessary for the efficient control of DWDS biofilms. However, biofilm studies are difficult to conduct in the actual DWDS because of inaccessibility to the pipes buried underground. Taking the opportunity of infrastructure construction and relevant pipeline replacement in China, biofilms in a DWDS (a water main and its branch pipes) were collected in situ, followed by analysis on the abundances and community structures of bacterial and archaeal using quantitative PCR and high-throughput sequencing, respectively. Results showed that archaea were detected only in the biofilms of the water main, with a range of 9.4×103~1.1×105 copies/cm2. By contrast, bacteria were detected in the biofilms of branch pipes and the distal part of the water main, with a range of 8.8×103~9.6×106 copies/cm2. Among the biofilm samples, the archaeal community in the central part of the water main showed the highest richness and diversity. Nitrosopumilus was found to be predominant (86.22%) in the biofilms of the proximal part of the water main. However, Methanobrevibacter (87.15%) predominated in the distal part of the water main. The bacterial community of the water main and branch pipes was primarily composed of Firmicutes and Proteobacteria at the phylum level, respectively. Regardless of archaea or bacteria, only few operational taxonomic units (OTUs) (<0.5% of total OTUs) were shared by all the biofilms, indicating the niche differentiation of biofilm microorganisms. Moreover, the high Mn content in the biofilms of the distal sampling location (D3) in the water main was linked to the predominance of Bacillus. Functional gene prediction revealed that the proportion of infectious disease-related genes was 0.44-0.67% in the tested biofilms. Furthermore, functional genes related to the resistance of the bacterial community to disinfections and antibiotics were detected in all the samples, that is, glutathione metabolism-relating genes (0.14-0.65%) and beta-lactam resistance gene (0.01-0.05%). The results of this study indicate the ubiquity of archaea and bacteria in the biofilms of water main and branch pipes, respectively, and pipe diameters could be a major influencing factor on bacterial community structure. In the water main, the key finding was the predominant existence of archaea, particularly Nitrosopumilus and methanogen. Hence, their routine monitoring and probable influences on water quality in pipelines with large diameter should be given more attention. Besides, since Mn-related Bacillus and suspected pathogenic Enterococcus were detected in the biofilm, supplementation of disinfectant may be a feasible strategy for inhibiting their growth and ensuring water quality. In addition, the monitoring on their abundance variation could help to determine the frequency and methods of pipeline maintenance.
摘要：
饮用水分配系统（DWDS）内表面上的生物膜会影响水质和稳定性。了解生物膜微生物群落的生态位分化对于有效控制DWDS生物膜是必要的。然而,生物膜的研究是很难在实际的DWDS进行，因为难以接近埋在地下的管道。以中国基础设施建设和相关管道更换为契机，就地收集DWDS（水总管及其分支管道）中的生物膜，然后使用定量PCR和高通量测序分析细菌和古细菌的丰度和群落结构，分别。结果表明，古细菌仅在水主干的生物膜中检测到，范围为9.4×103~1.1×105拷贝/cm2。相比之下,在支管和水管远端部分的生物膜中检测到细菌，范围为8.8×103~9.6×106拷贝/cm2。在生物膜样本中，水主干中部的古细菌群落显示出最高的丰富度和多样性。在水总管近端部分的生物膜中，发现亚硝唑属占主导地位（86.22％）。然而,甲烷杆菌（87.15％）在水总管的远端占主导地位。水主管和支管的细菌群落主要由门水平的Firmicutes和Proteobacteria组成。分别。不管是古细菌还是细菌,只有很少的操作分类单位（OTU）（<总OTU的0.5％）被所有生物膜共享，表明生物膜微生物的生态位分化。此外，水总管远端采样位置（D3）生物膜中的高Mn含量与芽孢杆菌的优势有关。功能基因预测显示，在测试的生物膜中，与传染病相关的基因的比例为0.44-0.67％。此外，在所有样本中检测到与细菌群落对消毒和抗生素抗性相关的功能基因，也就是说,谷胱甘肽代谢相关基因(0.14-0.65%)和β-内酰胺抗性基因(0.01-0.05%)。这项研究的结果表明，古细菌和细菌在水主管和支管的生物膜中普遍存在，分别,管径可能是影响细菌群落结构的主要因素。在水总管，关键的发现是古细菌的主要存在，特别是Nitrosopumilus和产甲烷菌。因此，它们的常规监测以及对大管径管道水质的可能影响应得到更多关注。此外,由于在生物膜中检测到锰相关的芽孢杆菌和可疑的致病性肠球菌，补充消毒剂可能是抑制其生长和确保水质的可行策略。此外,监测它们的丰度变化有助于确定管道维护的频率和方法。
