Dynamic bacterial communities on reverse-osmosis membranes in a full-scale desalination plant

To better understand biofouling of seawater reverse osmosis (SWRO) membranes, bacterial diversity was characterized in the intake water, in subsequently pretreated water and on SWRO membranes from a full-scale desalination plant (FSDP) during a 9 month period. 16S rRNA gene fingerprinting and sequencing revealed that bacterial communities in the water samples and on the SWRO membranes were very different. For the different sampling dates, the bacterial diversity of the active and the total bacterial fractions of the water samples remained relatively stable over the sampling period whereas the bacterial community structure on the four SWRO membrane samples was significantly different. The richness and evenness of the SWRO membrane bacterial communities increased with usage time with an increase in the Shannon diversity index of 2.2 to 3.7. In the oldest SWRO membrane (330 days), no single operational taxonomic unit (OTU) dominated and the majority of the OTUs fell into the Alphaproteobacteria or the Planctomycetes. In striking contrast, a Betaproteobacteria OTU affiliated to the genus Ideonella was dominant and exclusively found in the membrane used for the shortest time (10 days). This suggests that bacteria belonging to this genus could be one of the primary colonizers of the SWRO membrane. Knowledge of the dominant bacterial species on SWRO membranes and their dynamics should help guide culture studies for physiological characterization of biofilm forming species.为深入解析海水反渗透（seawater reverse osmosis, SWRO）膜的生物污损机制，本研究针对某全规模海水淡化厂（full-scale desalination plant, FSDP）为期9个月的运行周期内，其进水、后续预处理出水及SWRO膜表面的细菌多样性开展表征分析。采用16S rRNA基因指纹图谱技术与测序分析发现，水样与SWRO膜表面的细菌群落结构存在显著差异。在不同采样节点中，水样中活性与总细菌组分的细菌多样性在整个采样周期内始终保持相对稳定，但4份SWRO膜样品的细菌群落结构则呈现显著差异。随着膜组件运行时长增加，SWRO膜表面细菌群落的丰富度与均匀度均逐步提升，香农多样性指数从2.2升至3.7。在运行时长最长的SWRO膜（330天）样本中，无单一操作分类单元（operational taxonomic unit, OTU）占据主导地位，多数OTU隶属于α-变形菌纲（Alphaproteobacteria）或浮霉菌门（Planctomycetes）。与之形成鲜明对比的是，运行时长最短（10天）的膜表面仅存在1株隶属于β-变形菌纲（Betaproteobacteria）艾氏菌属（Ideonella）的OTU，并成为该样本的优势类群。上述结果表明，该菌属细菌可能是SWRO膜表面的早期定殖菌之一。明晰SWRO膜表面的优势细菌类群及其动态变化规律，可为生物膜形成菌株的生理特性研究提供指导方向。