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Due to daily human (anthropogenic) industrial activity, a lot of elemental mercury (Hg0) has been released to the atmosphere. The mercury can then spread globally, since mercury has the ability to remain atmospheric for up to a year. When mercury deposits, it can end up in anaerobic environments such as sediments and soil. In these oxygen-free climates, microbes such as Geobacter sulfurreducens exist. Such microbes can transform the mercury into another form, methylmercury, which is the most toxic and bio-transferrable type of mercury. This results in mercury accumulation throughout the food-chain, as smaller creatures are eaten by larger predators, concentrating the mercury in each consumption step. This is indeed concerning for humans, as we eat both mercury-accumulating plants and animals. The interesting phenomenon with G. sulfurreducens, is not only its ability to survive in an environment with mercury, but that it can take up the mercury inside itself to form methylmercury, and then excrete it to the external environment. However, the uptake mechanisms of mercury are poorly understood, whether the uptake is active or not (energy-dependent or independent), how many different uptake pathways exist, and if there are any working mercury transport proteins. Incidentally, thiol functional groups on the surface of the outer-membrane of the bacteria act as “anchoring-points” that mercury can bind to. Blocking of these anchoring-points in previous experiments has not shown any significant change in mercury methylation rates, in G. sulfurreducens. However, in this study, by utilizing a high concentration of a fluorophore (qbbr) to block the surface-thiols, we present data that indicate affected mercury distribution and methylation rates, when treating the cells with qbbr. Moreover, we examine the utilization of washing-methods to separate each sample into different fractions of mercury, investigating the cellular distribution of mercury. By separating samples in total, extracellular, intracellular, surface-adsorbed and methyl-mercury fractions, it appeared that the adsorbed and methylmercury fractions were affected and decreased by the qbbr blocking. Mercury analysis was accomplished by using cold-vapor ICP-MS, thermal desorption GC-ICP-MS and isotope dilution, as an internal standardization method.Furthermore, our microscopic analysis exhibited the notion that the Pi/Syto9 stained cells were stable, even with a relatively high concentration of qbbr, for the duration of the blocking experiments (4-5h after incubation).Understanding the uptake mechanisms of mercury, as well as the mercury methylation process, can lead to future innovations. The results in this study indicate that both uptake and methylation changed with blocked surface-thiols, which opens up for further research. Perhaps, in the future, it could aid the development of new bacterial-membrane filters, and methods to clean mercury polluted water, soil, and sediments.

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.

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Development and usage of poly-and perflourinated chemicals has increased considerablysince their discovery. They have since then polluted our environment and are exposed tohumans via drinking water and sea food amongst others. Regular waste water treatmentfacilities are not able to remove these chemicals despite their negative effect on humanhealth. I analysed the usability of ion exchange resin in a rotating bed reactor for removingpoly- and perflourinated chemicals from water. The capability of different resins to adsorbpoly- and perfluorinated chemicals was compared. These include Donau Carbon Epibon Y20x50; Purolite A592E and Purolite PFA694E as well as ECT2’s resin’s Sorbex regenerableand Sorbex LC4 non-regenerable. Kinetic studies were performed with ECt2’s Sorbexregenerable resin in a small scale and industrial scale version. The levels of poly- andperfluorinated chemicals left in the water after treatment was measured using liquidchromatography and mass spectrometry. The results showed that Sorbex ion exchange resinis the most effective adsorbent for treatment of industrial level volumes of water.

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