Earthworms and cadmium – heavy metal resistant gut bacteria as indicators for heavy metal pollution in soils?

Preservation of the soil resources stability is of high importance for ecosystems, particularly in the current era of environmental change, which presents a severe pollution burden (e.g. by heavy metals) to soil fauna. Gut microbiomes are becoming recognized as important players in organism health, with comprehension of their perturbations in the polluted environment offering new insights into the nature and extent of heavy metal effects on the health of soil biota. Our aim was to investigate the effect of environmentally relevant heavy metal concentrations of cadmium (Cd) on the earthworm (Lumbricus terrestris) gut microbiota. Our results revealed that Cd exposure led to perturbations of earthworm gut microbiota with an increase in bacteria previously described as heavy metal resistant or able to bind heavy metals, revealing the potential of the earthworm-gut microbiota system in overcoming human-caused heavy metal pollution. Furthermore, an ‘indicator species analysis’ linked the bacterial genera Paenibacillus, Flavobacterium and Pseudomonas, with Cd treatment, suggesting these bacterial taxa as biomarkers of exposure in earthworms inhabiting Cd-stressed soils. The results of this study help to understand the impact of anthropogenic disturbance on soil fauna health and will have implications for environmental monitoring and protection of soil resources.

土壤资源稳定性的维持对于生态系统而言至关重要，尤其在当前环境变化的时代背景下——当前的环境变化给土壤动物带来了严重的污染负荷（例如重金属污染）。肠道微生物组现已被认定为影响生物体健康的关键调控因子，解析其在污染环境中的扰动特征，可为阐明重金属对土壤生物健康的影响性质与程度提供全新认知。本研究旨在探究环境相关浓度的镉（Cd）对蚯蚓（Lumbricus terrestris）肠道微生物组的影响。研究结果显示，镉暴露会引发蚯蚓肠道微生物组的扰动，其中被此前研究认定为耐重金属或可结合重金属的细菌类群丰度显著上升，这表明蚯蚓-肠道微生物组系统具备应对人为源重金属污染的潜在能力。此外，“指示物种分析”将细菌属类芽孢杆菌属（Paenibacillus）、黄杆菌属（Flavobacterium）与假单胞菌属（Pseudomonas）与镉处理组关联起来，表明这些细菌类群可作为栖息于镉胁迫土壤中蚯蚓的暴露生物标志物。本研究结果有助于阐明人为干扰对土壤动物健康的影响，同时可为环境监测与土壤资源保护工作提供重要参考。