Matar Gerald K, Ali Muhammad, Bagchi Samik, Nunes Suzana, Liu Wen-Tso, Saikaly Pascal E
Biological and Environmental Science and Engineering Division, Water Desalination and Reuse Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Biological and Environmental Science and Engineering Division, Advanced Membranes and Porous Materials Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Front Microbiol. 2021 Sep 10;12:708531. doi: 10.3389/fmicb.2021.708531. eCollection 2021.
The relative importance of different ecological processes controlling biofilm community assembly over time on membranes with different surface characteristics has never been investigated in membrane bioreactors (MBRs). In this study, five ultrafiltration hollow-fiber membranes - having identical nominal pore size (0.1μm) but different hydrophobic or hydrophilic surface characteristics - were operated simultaneously in the same MBR tank with a constant flux of 10 liters per square meter per hour (LMH). In parallel, membrane modules operated without permeate flux (0 LMH) were submerged in the same MBR tank, to investigate the passive microbial adsorption onto different hydrophobic or hydrophilic membranes. Samples from the membrane biofilm were collected after 1, 10, 20, and 30days of continuous filtration. The membrane biofilm microbiome were investigated using 16S rRNA gene amplicon sequencing from DNA and cDNA samples. Similar beta diversity trends were observed for both DNA- and cDNA-based analyses. Beta diversity analyses revealed that the nature of the membrane surface (i.e., hydrophobic . hydrophilic) did not seem to have an effect in shaping the bacterial community, and a similar biofilm microbiome evolved for all types of membranes. Similarly, membrane modules operated with and without permeate flux did not significantly influence alpha and beta diversity of the membrane biofilm. Nevertheless, different-aged membrane biofilm samples exhibited significant differences. Proteobacteria was the most dominant phylum in early-stage membrane biofilm after 1 and 10days of filtration. Subsequently, the relative reads abundance of the phyla Bacteroidetes and Firmicutes increased within the membrane biofilm communities after 20 and 30days of filtration, possibly due to successional steps that lead to the formation of a relatively aged biofilm. Our findings indicate distinct membrane biofilm assembly patterns with different-aged biofilm. Ecological null model analyses revealed that the assembly of early-stage biofilm community developed after 1 and 10days of filtration was mainly governed by homogenous selection. As the biofilm aged (days 20 and 30), stochastic processes (e.g., ecological drift) started to become important in shaping the assembly of biofilm community.
在膜生物反应器（MBR）中，不同生态过程对具有不同表面特性的膜上生物膜群落随时间组装的相对重要性从未被研究过。在本研究中，五个超滤中空纤维膜——具有相同的标称孔径（0.1μm）但不同的疏水或亲水表面特性——在同一个MBR池中同时运行，通量恒定为每平方米每小时10升（LMH）。同时，将不通渗透通量（0 LMH）运行的膜组件浸没在同一个MBR池中，以研究微生物在不同疏水或亲水膜上的被动吸附。在连续过滤1、10、20和30天后，从膜生物膜中采集样本。使用来自DNA和cDNA样本的16S rRNA基因扩增子测序对膜生物膜微生物组进行研究。基于DNA和基于cDNA的分析都观察到了相似的β多样性趋势。β多样性分析表明，膜表面的性质（即疏水.亲水）似乎对塑造细菌群落没有影响，并且所有类型的膜都进化出了相似的生物膜微生物组。同样，有和没有渗透通量运行的膜组件对膜生物膜的α和β多样性没有显著影响。然而，不同老化程度的膜生物膜样本表现出显著差异。在过滤1天和10天后的早期膜生物膜中，变形菌门是最主要的门类。随后，在过滤20天和30天后，拟杆菌门和厚壁菌门在膜生物膜群落中的相对读数丰度增加，这可能是由于导致形成相对老化生物膜的演替步骤。我们的研究结果表明不同老化程度的生物膜具有不同的膜生物膜组装模式。生态零模型分析表明，过滤1天和10天后形成的早期生物膜群落的组装主要受同质选择支配。随着生物膜老化（第20天和第30天），随机过程（如生态漂变）开始在塑造生物膜群落组装中变得重要。
