摘要
      畜禽粪便是抗生素抗性基因（ARGs）的重要来源，其盐度水平在储存过程中会发生变化。为了了解盐度变化如何影响ARGs的命运，对牛粪的盐度进行了调整，并在实验室微宇宙中以低盐度（0.3%）、中等盐度（3.0%）和高盐度（10.0%）储存44天。在qPCR监测的五种ARGs（tetO、blaTEM、sul1、tetM和ermB）和一级整合酶（intI1）中，tetO和blaTEM的相对丰度对盐度水平没有明显的响应趋势，而sul1、tetM、ermB和intI1的相对丰度在较低盐度水平（0.3%和3%）下随时间呈明显下降趋势，但在高盐度水平（10%）下则没有。牛粪样本的宏基因组重叠群构建表明，sul1、tetM和ermB基因比tetO和blaTEM更可能与移动遗传元件（MGE）相关，这表明它们在较高盐度水平下的缓慢衰变要么是由水平基因转移引起的，要么是由ARGs和渗透胁迫抗性决定簇的共同选择引起的。对宏基因组重叠群的进一步分析表明，渗透胁迫抗性也可以位于MGE上或与ARGs结合。
Abstract
Livestock manure is an important source of antibiotic resistance genes (ARGs), and its salinity level can change during stockpiling. To understand how the salinity changes affect the fate of ARGs, cattle manure was adjusted of salinity and stockpiled in laboratory microcosms at low (0.3% salt), moderate (3.0%) and high salinity levels (10.0%) for 44 days. Amongst the five ARGs (tetO, blaTEM, sul1, tetM, and ermB) and the first-class integrase (intI1) monitored by qPCR, the relative abundance of tetO and blaTEM exhibited no clear trend in response to salinity levels, while that of sul1, tetM, ermB and intI1 showed clear downward trends over time at the lower salinity levels (0.3% and 3%) but not at the high salinity level (10%). Metagenomic contig construction of cattle manure samples revealed that sul1, tetM and ermB genes were more likely to associate with mobile genetic elements (MGEs) than tetO and blaTEM, suggesting that their slower decay at higher salinity levels was either caused by horizontal gene transfer or co-selection of ARGs and osmotic stress resistant determinants. Further analysis of metagenomic contigs showed that osmotic stress resistance can also be located on MGEs or in conjunction with ARGs.

https://www.sciencedirect.com/science/article/abs/pii/S0304389422023846