The effect of anthropogenic arsenic contamination on the earthworm microbiome

Abstract

Summary Earthworms are globally distributed and perform essential roles for soil health and microbial structure. We have investigated the effect of an anthropogenic contamination gradient on the bacterial community of the keystone ecological species L umbricus rubellus through utilizing 16 S rRNA pyrosequencing for the first time to establish the microbiome of the host and surrounding soil. The earthworm‐associated microbiome differs from the surrounding environment which appears to be a result of both filtering and stimulation likely linked to the altered environment associated with the gut micro‐habitat (neutral pH , anoxia and increased carbon substrates). We identified a core earthworm community comprising P roteobacteria (∼50%) and A ctinobacteria (∼30%), with lower abundances of B acteroidetes (∼6%) and A cidobacteria (∼3%). In addition to the known earthworm symbiont ( V erminephrobacter sp.), we identified a potential host‐associated G ammaproteobacteria species ( S erratia sp.) that was absent from soil yet observed in most earthworms. Although a distinct bacterial community defines these earthworms, clear family‐ and species‐level modification were observed along an arsenic and iron contamination gradient. Several taxa observed in uncontaminated control microbiomes are suppressed by metal/metalloid field exposure, including eradication of the hereto ubiquitously associated V erminephrobacter symbiont, which raises implications to its functional role in the earthworm microbiome.

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