The acid−base and Zn sorption properties of three
bacteria, Cupriavidus metallidurans CH34, Pseudomonas
putida ATCC12633, and Escherichia coli K12DH5α, were
investigated through an original combination of extended
X-ray absorption fine structure (EXAFS) spectroscopy and
equilibrium titration studies. Acid−base titration curves
of the three strains were fitted with a model accounting for
three conceptual reactive sites: an acidic (carboxyl and/or phosphodiester), a neutral (phosphomonoester), and
a basic (amine and/or hydroxyl) group. Calculated proton
and Zn equilibrium constants and site densities compare with
literature data. The nature of Zn binding sites was
studied by EXAFS spectroscopy. Phosphoester, carboxyl,
and unexpectedly sulfhydryl ligands were identified. Their
proportions depended on Zn loading and bacterial strain
and were consistent with the titration results. These findings
were compared to the structure and site density of the
major cell wall components. It appeared that the cumulated
theoretical site density of these structures (<2 Zn nm-2)
was much lower than the total site density of the investigated
strains (16−56 Zn nm-2). These results suggest a dominant
role of extracellular polymeric substances in Zn retention
processes, although Zn binding to inner cell components
cannot be excluded.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.