Development of in-situ sensors for direct quantification of metal speciation and bio-availability

Lead Research Organisation: Lancaster University
Department Name: Lancaster Environment Centre


Metals in the environment can be essential to life forms and so are regarded as micronutrients, but when excessive amounts are present they may be toxic. Current measurement and assessment of the metal that is available to biota is essential for optimising agriculture and aquaculture and for assessing ecological and human health. The uptake of metals by organisms is complicated and depends on the dynamics of exchange of the various chemical forms of the metal. For a measurement tool to assess successfully the bioavailable forms of the metal it must mimic the essential characteristics of the biota. The new technique of diffusive gradients in thin-films (DGT) emulates some aspects of the dynamics, but it lacks some essential features of the organism. This work will introduce controlled biological features into DGT to provide two new tools that can be used in situ to assess bioavailable metals. The biological binding DGT (BBDGT) will incorporate cell cultures to enable precise mimicry of uptake from solution. The biological mobilising DGT (BMDGT) will contain microbial components that can enable the measurement of metals capable of release from colloids and particles.


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Description Assessing metal bioavailability in soil is important in modeling the effects of metal toxicity on the surrounding ecosystem. Current methods based on diffusive gradient thin films (DGTs) and Gel-Integrated Microelectrode are limited in their availability and sensitivity. To address this, Shewanella oneidensis, an anaerobic iron reducing bacterium, was incorporated into a thin layer of agarose to replace the polyacrylamide gel that is normally present in DGT to form biologically mobilizing DGT (BMDGT). Viability analysis revealed that 16-35% of the cells remained viable within the BMDGTs depending on the culturing conditions over a 20 h period with/without metals. Deployment of BMDGTs in standardized metal solutions showed significant differences to cell-free BMDGTs when cells grown in Luria Broth (LB) were incorporated into BMDGTs and deployed under anaerobic conditions. Deployment of these BMDGTs in hematite revealed no significant differences between BMDGTs and BMDGTs containing heat killed cells. Whether heat killed cells retain the ability to affect bioavailability is uncertain. This is the first study to investigate how a microorganism that was incorporated into a DGT device such as the metal reducing bacteria, S. oneidensis, may affect the mobility of metals. Further work is on-going.
Exploitation Route As it was only a proof of concept grant, further researches are needed. Findings from the project may be taken forward by other scientists.
Sectors Environment