The effects of cadmium (Cd) contamination on the microbial community structure, soil physicochemistry and heavy metal resistome of a tropical agricultural soil were evaluated in field-moist soil microcosms. A Cd-contaminated agricultural soil (SL5) and an untreated control (SL4) were compared over a period of 5 weeks. Analysis of the physicochemical properties and heavy metals content of the two microcosms revealed a statistically significant decrease in value of the soil physicochemical parameters (P < 0.05) and concentration of heavy metals (Cd, Pb, Cr, Zn, Fe, Cu, Se) content of the agricultural soil in SL5 microcosm. Illumina shotgun sequencing of the DNA extracted from the two microcosms showed the predominance of the phyla, classes, genera and species of Proteobacteria (37.38%), Actinobacteria (35.02%), Prevotella (6.93%), and Conexibacter woesei (8.93%) in SL4, and Proteobacteria (50.50%), Alphaproteobacteria (22.28%), Methylobacterium (9.14%), and Methylobacterium radiotolerans (12,80%) in SL5, respectively. Statistically significant (P < 0.05) difference between the metagenomes was observed at genus and species delineations. Functional annotation of the two metagenomes revealed diverse heavy metal resistome for the uptake, transport, efflux and detoxification of various heavy metals. It also revealed the exclusive detection in SL5 metagenome of members of RND (resistance nodulation division) protein czcCBA efflux system (czcA, czrA, czrB), CDF (cation diffusion facilitator) transporters (czcD), and genes for enzymes that protect the microbial cells against cadmium stress (sodA, sodB, ahpC). The results obtained in this study showed that Cd contamination significantly affects the soil microbial community structure and function, modifies the heavy metal resistome, alters the soil physicochemistry and results in massive loss of some autochthonous members of the community not adapted to the Cd stress.

中文翻译：

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镉摄动对热带农业土壤微生物群落结构和重金属抵抗的影响

在田间潮湿的土壤微观世界中，评估了镉（Cd）污染对热带农业土壤微生物群落结构，土壤理化性质和重金属抵抗力的影响。在5周内比较了受Cd污染的农业土壤（SL5）和未经处理的对照（SL4）。对两个微观世界的理化性质和重金属含量的分析表明，土壤理化参数值（P < 0.05）和重金属浓度（Cd，Pb，Cr，Zn，Fe，Cu，Se）的含量在统计学上显着下降（P  <  0.05） SL5缩影中农业土壤的含量 从两个微观世界提取的DNA的Illumina shot弹枪测序表明，这些物种的门，种，属和种占优势SL4中的变形杆菌（37.38％），放线菌（35.02％），普罗沃氏菌（6.93％）和沃氏杆菌（8.93％）和变形杆菌（50.50％），α变形杆菌（22.28％），甲基杆菌（9.14％）和耐甲基杆菌（SL5）中的（12,80％）。具有统计意义（P <0.05）在属和物种描述中观察到了元基因组之间的差异。这两个元基因组的功能注释揭示了多种重金属抗药性，可用于各种重金属的吸收，转运，外排和排毒。它还揭示了在R5（抗性结节分裂）蛋白czcCBA外排系统（czcA，czrA，czrB），CDF（阳离子扩散促进剂）转运蛋白（czcD）的成员以及保护微生物细胞的酶基因中SL5元基因组中的独家检测。对抗镉胁迫（sodA，sodB，ahpC）。这项研究获得的结果表明，Cd污染会显着影响土壤微生物群落的结构和功能，改变重金属抗药性，改变土壤的理化性质，并导致一些不适应Cd胁迫的群落中的本地成员大量损失。