Lead homeostasis in extremophile earthworms: time and space resolved changes in metal speciation

Heavy metal pollution is a growing issue due to its persistency and routes of spread. Non-essential heavy metals such as lead exhibit deleterious effects through mimicry of essential elements e.g. calcium. Thus, lead bioaccumulation is known to disrupt the function of the central nervous system and has been associated with an early onset of neurodegenerative diseases. Earthworms populating heavy metal polluted landscapes have evolved distinct homeostatic mechanisms for metal detoxification. Omics-based approaches may: provide clues for treatment of metal toxicity; improved soil toxicity testing measures; advance soil vermiremediation research; determine mechanisms of earthworm quantum dot biosynthesis. Laser Ablation Inductively Coupled Plasma Mass Spectrometry imaging was used to compare lead bioaccumulation patterns in the brain and the gut of lead-resistant and control earthworms exposed to equal doses of lead in soil. Metallomic maps qualitatively revealed several biological adaptations including: accumulation of phenomenal amounts of lead in the gut (~30X greater than the control); low lead bioaccumulation in the brain (~10X lower than the control); precise lead sequestration into designated storage/detoxifying tissues (chloragogen tissues in gut, neuronal cell bodies in brain). Future studies will employ imaging mass cytometry, single cell transcriptomics, and synchrotron radiation to reveal molecular mechanisms of lead detoxification.