Influence of sulfhydryl sites on metal binding by bacteria

Thermodesulfobium sp. strain 3baa, an acidophilic sulfate reducing bacterium forming biofilms triggered by mineral precipitation

“…Instead, Fe 2+ interacts more strongly with other functional groups, such as sulfhydryl, imidazole, and phenyl groups, all of which are rarely displayed at the cell surface. Sulfhydryl groups account for only 5%–10% of the total binding sites on the cell surface and have a relatively high p Ka value of ~ 7 (Nell and Fein, ). This may explain why the precipitation of FeS is only minor at least on intact cells.…”

Metal internalization by bacterial cells depends on metal biotoxicity and metal to biomass ratio

“…Another possible explanation for the differences between low and high metal to biomass loading may be the identity of surface active ligands present on cell surfaces that are involved in metal binding. In particular, a number of studies have shown that metal ions preferentially bind to sulfhydryl (-S-H) groups on bacterial cell surfaces at low metal to biomass ratios, with other ligands (notably carboxyl, phosphate and amine functional groups) becoming important only at high metal to biomass ratios (Mishra et al, 2010;Yu and Fein, 2015;Nell and Fein, 2017). Consequently, we determined the identity of surface ligands on E. coli cells by performing surface complexation modelling of potentiometric (proton adsorption) titration data, along with infrared spectroscopy.…”

Role of bacterial cell surface sulfhydryl sites in cadmium detoxification by Pseudomonas putida

“…Compared to carboxyl and phosphoryl sites, sulfhydryl sites on bacterial cell surfaces are generally less abundant (Yu et al, 2014), but they form much stronger bonds with chalcophile 113 metals such as Hg, Cd, Zn, Cu and Au (Yu and Fein, 2015;Nell and Fein, 2017;Yu and Fein, 2017b), resulting in the dominance of sulfhydryl sites in the adsorption of these metals onto 115 bacterial cells under low metal loading conditions (Guine et al, 2006;Mishra et al, 2010;Pokrovsky et al, 2012;Yu and Fein, 2015). In addition, the concentration of sulfhydryl sites on bacterial cell surfaces can increase significantly as a function of growth conditions (Yu and Fein, 2017a), and hence sulfhydryl sites can contribute significantly to the adsorption of Cd, Hg and Au 119 onto bacterial cells even under high metal loadings (Mishra et al, 2017;Yu and Fein, 2017b).…”

“…The observed correlation is not limited to the 2 ppm Cd dataset, as the measured 2h growth factors in the 5, 10, and 20 ppm Cd experiments all exhibit strong correlations with cell surface sulfhydryl site concentrations ( Figure S4). The goodness of the correlations decreases in general with increasing Cd concentrations, likely because for the experiments with higher total Cd concentrations, the concentration of adsorbed Cd exceeds the concentration of sulfhydryl binding sites, and Cd in these systems also binds to some extent to non-sulfhydryl sites under these elevated metal loadings (Mishra et al, 2010;Yu and Fein, 2015;Nell and Fein, 2017). This result is consistent with 452 sulfhydryl sites playing a crucial role in diminishing Cd toxicity, and for the high Cd systems in 453 which significant non-sulfhydryl binding occurs, Cd toxicity increases and the relationship 454 between sulfhydryl site concentration and Cd toxicity breaks down to some extent.…”