Looking for lipases and lipolytic organisms in low-temperature anaerobic reactors treating domestic wastewater
Looking for lipases and lipolytic organisms in low-temperature anaerobic reactors treating domestic wastewater
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DOI：
10.1101/2021.11.16.468786
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
R. Bashiri;B. Allen;B. Shamurad;M. Pabst;T. Curtis;I. D. Ofiţeru
中科院分区：
文献类型：
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作者：
R. Bashiri;B. Allen;B. Shamurad;M. Pabst;T. Curtis;I. D. Ofiţeru
即使使用嗜冷菌，脂质降解不良也限制了生活废水的低温厌氧处理。我们结合宏基因组学和宏蛋白质组学，在 4°C 和 15°C 处理生活废水的厌氧膜生物反应器中寻找脂肪分解细菌及其潜力，以及实际的冷适应细胞外脂肪酶。在 40 个回收的假定脂肪分解宏基因组组装基因组 (MAG) 中，只有三种（绿菌属、脱硫杆菌属和分枝杆菌属）在所有反应器中常见且丰富（相对丰度≥ 1%）。值得注意的是，一些代表需氧自养生物的 MAG 含有脂肪酶。因此，我们假设我们发现的脂肪酶并不总是与外源脂质降解相关，并且可以具有其他作用，例如聚羟基脂肪酸酯（PHA）积累/降解以及干扰其他细菌的外膜。尽管四个属（脱氯单胞菌属、固氮弧菌属、气单胞菌属和硫单胞菌属）的 fadL 基因（长链脂肪酸转运蛋白）的表达得到证实，但宏蛋白质组学并未为相对较低丰度的蛋白质（如脂肪酶）提供足够的蛋白质组覆盖，但没有一个属被恢复为假定的脂肪分解 MAG。宏蛋白质组学还证实了所有反应器中存在 15 个相对丰富 (≥1%) 的属，其中至少 6 个可以潜在地积累脂质/聚羟基脂肪酸酯。对于大多数假定的脂肪分解 MAG，读数丰度和反应器条件（例如温度、相（生物膜和散装液体）和进料类型（是否经过紫外线处理））之间不存在统计显着相关性。宏基因组学和宏蛋白质组学获得的结果并不能相互证实，需要进一步的工作来识别这些系统中真正的脂质降解剂。
Poor lipid degradation limits low-temperature anaerobic treatment of domestic wastewater even when psychrophiles are used. We combined metagenomics and metaproteomics to find lipolytic bacteria and their potential, and actual, cold-adapted extracellular lipases in anaerobic membrane bioreactors treating domestic wastewater at 4°C and 15°C. Of the 40 recovered putative lipolytic metagenome-assembled genomes (MAGs), only three (Chlorobium, Desulfobacter, and Mycolicibacterium) were common and abundant (relative abundance ≥ 1%) in all reactors. Notably, some MAGs that represented aerobic autotrophs contained lipases. Therefore, we hypothesised that the lipases we found are not always associated with exogenous lipid degradation and can have other roles such as polyhydroxyalkanoates (PHA) accumulation/degradation and interference with the outer membranes of other bacteria. Metaproteomics did not provide sufficient proteome coverage for relatively lower abundant proteins such as lipases though the expression of fadL genes, long-chain fatty acid transporters, was confirmed for four genera (Dechloromonas, Azoarcus, Aeromonas and Sulfurimonas), none of which were recovered as putative lipolytic MAGs. Metaproteomics also confirmed the presence of 15 relatively abundant (≥1%) genera in all reactors, of which at least 6 can potentially accumulate lipid/polyhydroxyalkanoates. For most putative lipolytic MAGs, there was no statistically significant correlation between the read abundance and reactor conditions such as temperature, phase (biofilm and bulk liquid), and feed type (treated by ultraviolet light or not). Results obtained by metagenomics and metaproteomics did not confirm each other and further work is required to identify the true lipid degraders in these systems.