Rios-Miguel Ana B, Smith Garrett J, Cremers Geert, van Alen Theo, Jetten Mike S M, Op den Camp Huub J M, Welte Cornelia U
Department of Microbiology, Radboud University, Radboud Institute for Biological and Environmental Sciences, Heyendaalseweg 135, Nijmegen 6525 AJ, the Netherlands.
Soehngen Institute of Anaerobic Microbiology, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ, the Netherlands.
Water Res X. 2022 Aug 4;16:100152. doi: 10.1016/j.wroa.2022.100152. eCollection 2022 Aug 1.
Pharmaceuticals are relatively new to nature and often not completely removed in wastewater treatment plants (WWTPs). Consequently, these micropollutants end up in water bodies all around the world posing a great environmental risk. One exception to this recalcitrant conversion is paracetamol, whose full degradation has been linked to several microorganisms. However, the genes and corresponding proteins involved in microbial paracetamol degradation are still elusive. In order to improve our knowledge of the microbial paracetamol degradation pathway, we inoculated a bioreactor with sludge of a hospital WWTP (Pharmafilter, Delft, NL) and fed it with paracetamol as the sole carbon source. Paracetamol was fully degraded without any lag phase and the enriched microbial community was investigated by metagenomic and metatranscriptomic analyses, which demonstrated that the microbial community was very diverse. Dilution and plating on paracetamol-amended agar plates yielded two sp. isolates: a fast-growing sp. that degraded 200 mg/L of paracetamol in approximately 10 h while excreting 4-aminophenol, and a slow-growing sp. that degraded paracetamol without obvious intermediates in more than 90 days. Each sp. contained a different highly-expressed amidase (31% identity to each other). These amidase genes were not detected in the bioreactor metagenome suggesting that other as-yet uncharacterized amidases may be responsible for the first biodegradation step of paracetamol. Uncharacterized deaminase genes and genes encoding dioxygenase enzymes involved in the catabolism of aromatic compounds and amino acids were the most likely candidates responsible for the degradation of paracetamol intermediates based on their high expression levels in the bioreactor metagenome and the spp. genomes. Furthermore, cross-feeding between different community members might have occurred to efficiently degrade paracetamol and its intermediates in the bioreactor. This study increases our knowledge about the ongoing microbial evolution towards biodegradation of pharmaceuticals and points to a large diversity of (amidase) enzymes that are likely involved in paracetamol metabolism in WWTPs.
药物相对来说是自然界中的新物质，在污水处理厂（WWTPs）中往往不能被完全去除。因此，这些微污染物最终进入世界各地的水体，带来巨大的环境风险。对乙酰氨基酚是这种难降解转化的一个例外，其完全降解与几种微生物有关。然而，参与微生物对乙酰氨基酚降解的基因和相应蛋白质仍然不清楚。为了增进我们对微生物对乙酰氨基酚降解途径的了解，我们用一家医院污水处理厂（荷兰代尔夫特的Pharmafilter）的污泥接种了一个生物反应器，并以对乙酰氨基酚作为唯一碳源投喂。对乙酰氨基酚在没有任何滞后期的情况下被完全降解，通过宏基因组学和宏转录组学分析对富集的微生物群落进行了研究，结果表明该微生物群落非常多样化。在添加了对乙酰氨基酚的琼脂平板上进行稀释和平板划线培养，得到了两个菌株：一个生长迅速的菌株，在大约10小时内降解了200mg/L的对乙酰氨基酚，同时分泌4-氨基苯酚；另一个生长缓慢的菌株，在90多天内降解对乙酰氨基酚且没有明显的中间产物。每个菌株都含有一种不同的高表达酰胺酶（彼此之间有31%的同源性）。在生物反应器宏基因组中未检测到这些酰胺酶基因，这表明其他尚未鉴定的酰胺酶可能负责对乙酰氨基酚的第一步生物降解。基于它们在生物反应器宏基因组和菌株基因组中的高表达水平，未鉴定的脱氨酶基因以及编码参与芳香族化合物和氨基酸分解代谢的双加氧酶的基因最有可能是负责对乙酰氨基酚中间产物降解的候选基因。此外，不同群落成员之间可能发生了交叉喂养，以在生物反应器中有效降解对乙酰氨基酚及其中间产物。这项研究增加了我们对正在进行的微生物向药物生物降解进化的了解，并指出了可能参与污水处理厂中对乙酰氨基酚代谢的多种（酰胺酶）酶。
