Mercury (Hg) is a naturally occurring trace element and pollutant that is ubiquitous in aquatic ecosystems. All Hg species are hazardous, but methylmercury (MeHg) is the most alarming due to its neurotoxicity, teratogenicity, and bioaccumulation in the food web. Humans risk exposure through fish consumption, so MeHg is of major health and environmental concern. MeHg is chiefly synthesized by anaerobic bacteria with the hgcAB gene cluster, like the δ-proteobacterium Geobacter sulfurreducens. However, the Hg uptake mechanism remains elusive. Both active and passive transport models have been proposed, and cell surface thiols serve important roles. This study aimed to characterize the Hg uptake at the inner membrane of G. sulfurreducens using protoplasts. The effects of added cysteine and glutathione, and of blocking Hg-thiol interactions with a thiol-binding ligand, qBBr, on Hg’s methylation and partitioning between extracellular, intracellular, and membrane-adsorbed fractions, were explored. After the fact, it was discovered that a mixture of spheroplasts, protoplasts, and several intermediates had been formed by the protocols. Cysteine addition made no difference compared with no thiol addition, but glutathione may have increased the extracellular Hg content. Compared with controls, qBBr-treated spheroplasts seemed to have higher extracellular Hg levels and lower MeHg production. However, all results were ambiguous due to high experimental uncertainty and low statistical significance. Despite the study’s shortcomings, it seems worthwhile to study Hg uptake at the inner membrane, but the experimental protocols must be redesigned to do so.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-189177 |
| Date | January 2021 |
| Creators | Eriksson, Andreas |
| Publisher | Umeå universitet, Kemiska institutionen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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