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.ImportanceSoil 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.

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

“…Chryseobacterium solincola can grow despite the elevated presence of highly toxic metals and has been suggested as a candidate for the situ bioremediation of heavy metals in aqueous or soil systems (50). Agrobacterium tumefaciens is able to survive in regions containing high levels of heavy metals and possesses various transporters involved in Ni, Cu, Zn and Cr resistance (51,52).…”

“…Metal-polluted soils also strongly influence soil microbiota and the microbiota of soil organisms. Several studies have shown a decrease in microbe biodiversity in metal-polluted soils (3)(4)(5). For instance, Cd inhibits microbial reproduction in soil (6), and Cd, copper (Cu), nickel (Ni), lead (Pb), chromium (Cr), arsen (As) and zinc (Zn) have been found to decrease the biomass, species richness and activity of microbial communities in forest and arable soils (7)(8)(9)(10).…”

Bacterial morphotypes as biodiversity indicators in a scarcely explored ecosystem in Santiago de Cali, Colombia

“…Bacteria are the most abundant microorganisms in the world and their diversity has not yet been completely elucidated [30][31][32][33][34] . In the environmental eld, bacteria have been useful in the analysis of water quality 35,36 , in the evaluation of soil contamination 37,38 , and as the indicators of food quality 39,40 .…”

The Effects of In Vivo Exposure to Copper Oxide Nanoparticles on the Gut Microbiome, Host Immunity, and Susceptibility to a Bacterial Infection in Earthworms

“…Loss of some core earthworm symbionts can lead to reduced host fitness and juvenile development [ 51 , 52 ]. Environmental pollutants can alter the microbiome of earthworms [ 53 , 54 , 55 , 56 ] and lead to the loss of core symbionts important to host health [ 57 ]. An increasing body of literature now indicates that exposure to NMs can also disrupt the microbiome of soil invertebrates [ 58 , 59 , 60 ].…”