摘要

    在不同温度下，厌氧消化（AD）系统中各种抗生素抗性基因（ARG）的命运仍然未知。这项研究采用了散弹枪宏基因组测序和16S rRNA扩增子测序方法，并研究了温度升高的AD系统（从35°C到55°C）中超过1360个ARG和微生物群落的组成和丰度变化。处理市政污水污泥。结果表明，消化的污泥中主要有6种ARG，包括macB，tetA（58），bcrA，evgS，mtrA和oleC。在高温条件下，可以大量减少超过407ARG的亚型（30％）。与嗜温性AD（35°C）相比，嗜热性AD（55°C）可更好地去除四环素，大环内酯，戊酰胺，氟喹诺酮，a啶染料和肽抗性基因。这些基因的去除率达到29.7％–32.3％。此外，在高温消化过程结束时，沙门氏菌的相对丰度增加了（从18.22％降低到74.89％），而变形杆菌和绿弯曲菌都降低了，从36.39％降低到6.80％和20.29％–2.64％。这项研究进一步提出了通过以下途径有效消除ARG的潜在机制：（1）减少抗生素外排泵的编码基因；（2）促进污泥生物量的降解速度；（3）丧失微生物群落多样性。 AD系统，以及（4）使多药耐药细菌失活。当前研究的意义在于表征整个AD过程中ARG的命运，从而使各种遗传特性与消化池的运行状况相关联。结果为深入了解如何利用AD技术（例如温度）有效地从市政污水污泥中去除ARGs提供了见识。

    The fate of diverse antibiotic resistance genes (ARGs) in anaerobic digestion (AD) system under different temperature remains largely unknow. This study employed the shotgun metagenomic sequencing and 16S rRNA amplicon sequencing approaches and investigated the shifts of composition and abundance of more than 1360 ARGs, as well as microbial community, in a temperature-raising AD system (from 35 °C to 55 °C) treating municipal sewage sludge. Results suggested that the six ARGs, inlcuding macB, tetA(58), bcrA, evgS, mtrA, and oleC, were predominated in digested sludge. More than 407ARG subtypes (30%) could be largely reduced under high temperature condition. Thermophilic AD (55 °C) provided a better removal for tetracycline, macrolide, penam, fluoroquinolone, acridine dye, and peptide resistance genes when compared to mesophilic AD (35 °C). The removal rates of these genes reached 29.7%–32.3%. In addition, at the end of thermophilic digestion process, the relative abundance of Firmicutes increased (from 18.22% to 74.89%), while Proteobacteria and Chloroflexi both decreased, from 36.39% to 6.80% and 20.29%–2.64%. This study further proposed the underlying mechanisms of effective elimination of ARGs under high temperature by: (1) the reduction of genes encoding antibiotic efflux pump, (2) the promotion of sludge biomass degradation rate, (3) the loss of microbial community diversity in AD systems, and (4) the inactivation of multidrug-resistant bacteria. The significance of current study is in characterizing the fate of ARGs across AD process, which allows to correlate diverse genetic properties with digesters’ operational condition. Results provided an insight into the manipulation of AD technology (e.g. temperature) to efficiently remove ARGs from municipal sewage sludge.

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