Earthworms and Cadmium - heavy metal resistant gut bacteria as indicators for heavy metal pollution in soils?

Abstract

Preservation of the soil resources stability is of paramount importance for the ecosystem, particularly in the current era of environmental change, which presents a severe pollution burden (e.g. by heavy metals) to soil ecosystems and its 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 therefore to evaluate the effect of environmentally relevant heavy metal concentrations of cadmium (Cd) on the earthworm gut microbiota. Cd exposure led to perturbations of several heavy metal resistant taxa as well as taxa able to bind heavy metals, revealing the potential of the earthworm-microbiota system in overcoming humancaused heavy metal pollution. An indicator species analysis linked bacterial genera Paenibacillus and Flavobacterium, and members of the order Actinomycetales with Cd treatment, suggesting the possible use of these bacterial taxa as biomarkers of exposure for Cd stressed soils. The results of this study will be essential to understanding of the soil fauna health, under anthropogenic disturbance, and will have implications for environmental monitoring and protection of soil resources.\n\nImportanceSoil heavy metal pollution presents a severe burden for soil invertebrates and can have impact on their health, which in turn reflects on the health of the entire ecosystem. Gut microbiome is recognized as a central driver of the host health and its shifts can have severe consequences for the host. In this study we investigated the impact of cadmium (Cd) on earthworm gut microbiota, in a controlled experiment using cutting edge next generation sequencing and state of the art bioinformatics tools. The significance of this study is in identifying the gut bacterial taxa which are indicators for Cd treatment and are potential biomarkers of exposure to Cd. Therefore, this study contributes to develop efficient measures to qualify environmental pollution and to protect fragile soil resources and ultimately human health.