摘要
      镉广泛分布于水生环境中，对象牙壳等水生生物有多种不利影响。然而，它对乳晕双歧杆菌抗生素抗性基因（ARGs）和肠道微生物群的影响尚不清楚。在本研究中，我们通过16S rRNA基因测序和高通量定量PCR，探讨了不同浓度（0、0.03、0.18和1.08mg/L）的镉对乳晕双歧杆菌肠道微生物群落和ARGs的影响。结果表明，镉暴露后，乳晕双歧杆菌肠道中ARGs和微生物群的结构和多样性发生了改变。四环素、万古霉素和大环内酯类林肯酰胺链霉菌B（MLSB）抗性基因被鉴定为乳晕双歧杆菌肠道中的主要ARGs。随着镉浓度的升高，乳晕双歧杆菌肠道中ARGs的绝对丰度和α多样性增加。与对照组相比，属水平的微生物群落在低和中等镉浓度组中富集，而在高镉浓度组则减少。此外，微生物群对乳晕双歧杆菌ARG谱的影响比镉浓度和MGE的影响更显著。零模型分析表明，随机过程主导了镉暴露组的ARG组装，并随着镉浓度的增加而增强。在乳晕双歧杆菌肠道中检测到的四种机会性细菌病原体（拟杆菌、军团菌、不动杆菌和大肠杆菌）可能是ARGs的潜在宿主。我们的研究结果为水生动物肠道微生物组环境镉暴露的危害评估提供了参考。
Abstract
Cadmium (Cd) is widely distributed in aquatic environments and has multiple adverse effects on aquatic organisms such as the ivory shell (Babylonia areolata). However, its effects on antibiotic resistance genes (ARGs) and gut microbiota of B. areolata remain unclear. In this study, we explored the effects of different concentrations (0, 0.03, 0.18 and 1.08 mg/L) of Cd on intestinal microbial communities and ARGs in B. areolata through 16S rRNA gene sequencing and high-throughput quantitative PCR. The results showed that the structure and diversity of ARGs and microbiota in B. areolata gut were altered upon Cd exposure. Tetracycline, Vancomycin and Macrolide-Lincosamide-Streptogramin B (MLSB) resistance genes were identified as the major ARGs in B. areolata gut. The absolute abundance and alpha diversity of ARGs in B. areolata gut increased with the rise of cadmium concentration. The microbial communities at genus level were enriched in the low and medium Cd concentration groups, while decreased in the high Cd concentration group compared to the control groups. In addition, the influence of microbiota on the ARG profile was more significant than that of Cd concentration and MGEs in B. areolata gut. Null model analysis demonstrated that stochastic processes dominated ARG assembly in the Cd-exposed groups and were enhanced with the increasing Cd concentrations. Four opportunistic bacterial pathogens (Bacteroides, Legionella, Acinetobacter and Escherichia) detected in B. areolata gut maybe the potential hosts of ARGs. Our findings provide references for the hazards assessment of environmental Cd exposure of gut microbiome in aquatic animals.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722083474