Although membrane fouling is a major issue when operating membrane bioreactors (MBRs), information regarding MBR performance and the sludge microbiome after the development of fouling remains limited. For the present study, two MBRs were operated for approximately 1 month under conditions of membrane fouling to investigate the effects of highly stressed environments on the sludge microbiome. After the development of fouling, a Collimonas-related operational taxonomic unit (OTU) was highly dominant in both reactors (relative abundances were ⁓ 63%) and this predomination caused a precipitous decline in the diversity indices of the sludge microbiomes. Because the excessive predomination by limited numbers of OTUs can lead to reductions in the adaptability to environmental changes, monitoring microbial diversity may be a valuable indicator for maintaining the robustness of a sludge microbiome. While, the decrease in the abundance of the Collimonas-related OTU resulted in the predomination of distinct microorganisms in each of the reactors despite being operated under the same conditions; this finding indicates existence of strong pressure to perturb the microbiomes. Detailed analyses suggested that the availability of terminal electron acceptors and competitive interactions between microbes via the secretion of extracellular proteins appeared to differentiate the structures of the respective microbial communities. During the extracellular proteins were secreted in the sludge, considerable portion of microbes were dead and large amounts of biomolecules seemed to be released; resultantly facilitated the predomination of fermentative anaerobes in one reactor as they use organic substances but not inorganic terminal electron acceptors to generate ATP under anaerobic conditions.

中文翻译：

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在膜生物反应器（MBR）中发生膜污染后，微生物群落结构的转变。

尽管膜结垢是操作膜生物反应器（MBR）时的主要问题，但结垢发生​​后有关MBR性能和污泥微生物组的信息仍然有限。对于本研究，两个MBR在膜污染条件下运行了大约1个月，以研究高压力环境对污泥微生物组的影响。结垢发生后，在两个反应器中，与Collimonas相关的操作生物分类单元（OTU）都占主导地位（相对丰度约为63％），这种占主导地位导致了污泥微生物群落多样性指数的急剧下降。由于有限数量的OTU过度占主导地位会导致对环境变化的适应性下降，监测微生物多样性可能是保持污泥微生物组健壮性的重要指标。尽管与Collimonas相关的OTU的丰度降低，尽管在相同条件下运行，但每个反应器中的主要微生物仍占优势。这一发现表明存在强大的压力来干扰微生物组。详细的分析表明，末端电子受体的可用性和微生物之间通过细胞外蛋白分泌的竞争性相互作用似乎可以区分各个微生物群落的结构。在污泥中分泌细胞外蛋白的过程中，相当一部分微生物死亡，并且似乎释放出大量生物分子。