The toxicity of heavy metals and common resistance mechanisms used by bacteria and fungi to survive in toxic metal conditions are discussed. Applications of metal-tolerant microorganisms include the bioremediation of metal-polluted land and water, and the recovery of metals from industrial wastes. Microorganisms capable of metal ion reduction can be used to synthesise nanoparticles (NPs) providing a green alternative to conventional chemical production. This project aimed to isolate Cu-tolerant bacteria and fungi from Cu-rich natural and industrial environments which could synthesise catalytic Cu-NPs or be used for the bioremediation of Cu contaminated land. This project also aimed to increase the Cu-tolerance of a known Cu-reducing bacterium, Shewanella oneidensis, to increase its efficiency in synthesising Cu-NPs. A bacterial community grown from soil collected from a former Cu mine in Alderley Edge using a Cu-rich medium, synthesised Cu and Cu2S-NPs in the presence of 300 ÂµM Cu(II) and 500 ÂµM Cu(II). Multiple bacteria were implicated in synthesising the NPs based on associations between cells and Cu visible using a TEM. 16S rRNA gene Illumina sequencing identified a bacterium which most closely matches Geothrix fermentans as a dominant member of the community. G. fermentans, an Fe(III)-reducing bacterium, is a promising candidate for facilitating Cu(II) bioreduction. The bacterial community could potentially be used for Cu biorecovery from industrial waste. Future work includes the isolation of individual species to determine which are responsible for the different NPs, and to measure the efficiency of Cu(II) removal and Cu-NP production. Cu-tolerant fungi were also isolated from Alderley Edge and a Cu-rich effluent from a whisky distillery. The majority of the fungi identified were closely matched to members of the Penicillium genus, and Cu was identified in nanoparticles or biominerals that also contained elements including Na, Cl and K. Further work is required to identify their potential to remove Cu from solution. Immobilisation of Cu(II) by these fungal species could potentially be applied to remediate Cu-contaminated sites. To increase the Cu-tolerance of S. oneidensis, the Cu(II) concentration of a defined growth medium was increased incrementally. However, the S. oneidensis culture became contaminated and was out competed by Paraburkholderia fungorum. P. fungorum exhibited high Cu-tolerance but did not synthesise Cu- NPs under the experimental conditions tested. The experiments would need to be repeated to determine if the Cu-tolerance of S. oneidensis could be increased.
|Date of Award||31 Dec 2019|
- The University of Manchester
|Supervisor||Jonathan Lloyd (Supervisor)|