King Abdullah University of Science and Technology, Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Research Center, Thuwal 23955-6900, Saudi Arabia.
Baswood Corporation, Allen, TX 75013, USA.
Water Res. 2017 Oct 15;123:124-133. doi: 10.1016/j.watres.2017.06.052. Epub 2017 Jun 20.
Finding efficient biofouling control strategies requires a better understanding of the microbial ecology of membrane biofilm communities in membrane bioreactors (MBRs). Studies that characterized the membrane biofilm communities in lab-and pilot-scale MBRs are numerous, yet similar studies in full-scale MBRs are limited. Also, most of these studies have characterized the mature biofilm communities with very few studies addressing early biofilm communities. In this study, five full-scale MBRs located in Seattle (Washington, U.S.A.) were selected to address two questions concerning membrane biofilm communities (early and mature): (i) Is the assembly of biofilm communities (early and mature) the result of random immigration of species from the source community (i.e. activated sludge)? and (ii) Is there a core membrane biofilm community in full-scale MBRs? Membrane biofilm (early and mature) and activated sludge (AS) samples were collected from the five MBRs, and 16S rRNA gene sequencing was applied to investigate the bacterial communities of AS and membrane biofilms (early and mature). Alpha and beta diversity measures revealed clear differences in the bacterial community structure between the AS and biofilm (early and mature) samples in the five full-scale MBRs. These differences were mainly due to the presence of large number of unique but rare operational taxonomic units (∼13% of total reads in each MBR) in each sample. In contrast, a high percentage (∼87% of total reads in each MBR) of sequence reads was shared between AS and biofilm samples in each MBR, and these shared sequence reads mainly belong to the dominant taxa in these samples. Despite the large fraction of shared sequence reads between AS and biofilm samples, simulated biofilm communities from random sampling of the respective AS community revealed that biofilm communities differed significantly from the random assemblages (P < 0.001 for each MBR), indicating that the biofilm communities (early and mature) are unlikely to represent a random sample of the AS community. In addition to the presence of unique operational taxonomic units in each biofilm sample (early or mature), comparative analysis of operational taxonomic units and genera revealed the presence of a core biofilm community in the five full-scale MBRs. These findings provided insight into the membrane biofilm communities in full-scale MBRs. More comparative studies are needed in the future to elucidate the factors shaping the core and unique biofilm communities in full-scale MBRs.
寻找高效的生物污损控制策略需要更好地了解膜生物反应器（MBR）中膜生物膜群落的微生物生态学。描述实验室和中试规模 MBR 中膜生物膜群落的研究很多，但在全规模 MBR 中的类似研究却很有限。此外，这些研究大多描述了成熟的生物膜群落，而很少有研究涉及早期生物膜群落。在这项研究中，选择了五个位于西雅图（美国华盛顿州）的全规模 MBR，以解决有关膜生物膜群落（早期和成熟）的两个问题：（i）生物膜群落（早期和成熟）的组装是物种从源群落（即活性污泥）随机传入的结果吗？（ii）在全规模 MBR 中是否存在核心膜生物膜群落？从五个 MBR 中采集了膜生物膜（早期和成熟）和活性污泥（AS）样品，并应用 16S rRNA 基因测序来研究 AS 和膜生物膜（早期和成熟）的细菌群落。α和β多样性测量结果表明，五个全规模 MBR 中 AS 和生物膜（早期和成熟）样品之间的细菌群落结构存在明显差异。这些差异主要是由于每个样品中存在大量独特但罕见的操作分类单元（每个 MBR 中的总读数约为 13%）。相比之下，每个 MBR 中 AS 和生物膜样品之间的序列读数有很高的百分比（每个 MBR 中的总读数约为 87%）是共享的，这些共享的序列读数主要属于这些样品中的优势分类群。尽管 AS 和生物膜样品之间存在大量共享的序列读数，但从各自 AS 群落的随机抽样模拟生物膜群落表明，生物膜群落与随机组合有显著差异（每个 MBR 均<0.001），这表明生物膜群落（早期和成熟）不太可能代表 AS 群落的随机样本。除了每个生物膜样品（早期或成熟）中存在独特的操作分类单元外，对操作分类单元和属的比较分析表明，在五个全规模 MBR 中存在核心生物膜群落。这些发现为全规模 MBR 中的膜生物膜群落提供了深入了解。未来需要进行更多的比较研究，以阐明塑造全规模 MBR 中核心和独特生物膜群落的因素。
