Tellurite Adsorption onto Bacterial Surfaces

Tellurium
(Te) is an emerging contaminant and its chemical transformation
in the environment is strongly influenced by microbial processes.
In this study, we investigated the adsorption of tellurite [Te­(IV),
TeO32–] onto the common soil bacterium Bacillus subtilis. Thiol-blocking experiments were carried
out to investigate the role of cell surface sulfhydryl sites in tellurite
binding, and extended X-ray absorption fine structure (EXAFS) spectroscopy
was performed to determine the chemical speciation of the adsorbed
tellurite. The results indicate that tellurite reacts with sulfhydryl
functional groups in the extracellular polymeric substances (EPS)
produced by B. subtilis. Upon binding to sulfhydryl
sites in the EPS, the Te changes from Te–O bonds to Te–S
coordination. Further analysis of the surface-associated molecules
shows that the EPS of B. subtilis contain proteins.
Removal of the proteinaceous EPS dramatically decreases tellurite
adsorption and the sulfhydryl surface site concentration. These findings
indicate that sulfhydryl binding in EPS plays a key role in tellurite
adsorption on bacterial surfaces.