Reduction of chalcogen oxyanions and generation of nanoprecipitates by the photosynthetic bacterium Rhodobacter capsulatus

Recovery of Elemental Tellurium Nanoparticles by the Reduction of Tellurium Oxyanions in a Methanogenic Microbial Consortium

“…The findings of this research are in agreement with the information reported for the reduction of Te IV using lawsone as RM. Lawsone almost doubled the Te IV reduction rate when pyruvate was used as carbon source for the photosynthetic bacterium Rhodobacter capsulatus ; however, stimulation was reported to be independent of the lawsone concentration [29] . In a second study, lawsone increased the Te IV reduction rate of the bacterium E. coli by 10-fold when glucose was used as carbon source [30] and the rate of reduction was dependent of the lawsone concentration.…”

“…According to the standard redox potentials (E 0 ’ for pH 7) of the chemical species involved in these reductions, 2H + /H 2 E 0’ =−0.414 V [49] ; RF E 0’ = −0.208 V [50] ; lawsone E 0 ’= −0.145 V [29] ; HTeO 4 − /HTeO 3 − E 0 ’= 0.399 V; HTeO 3 − /Te 0 E 0 ’ = 0.196 V (calculated from E 0 values [40] ) the two RM compounds would be potentially effective electron shuttles, since their redox potentials are between those of the electron donor and electron acceptor reactions (H 2 oxidation and Te oxyanions reduction). The failure of HCB 12 to act as a RM might be explained by the highly negative redox potential of HCB 12 (E 0 = −0.530V [51] ) that was outside of the range.…”

“…As was observed with Te VI -reduction, the RMs, achieved a high fraction of extracellularly dispersed Te faster during Te IV reduction, requiring only 0.3 days compared to 2 days when the bioassay lacked the RM. The effectiveness of lawsone to enhance the extracellular precipitation of Te 0 and Se 0 from Te IV and Se IV oxyanions has also been reported for E. coli in systems amended with glucose as an electron donor and Te/Se:RM molar ratios of 10:1 through 1.7:1 [30] and for the photosynthetic bacteria R. capsulatus using pyruvate as the carbon source and a Te:RM molar ratio 5:1 [29] ; the increase of extracellular material when the RM was added to the experimental system was assessed based on qualitative observations. An increase in the formation of extracellular NPs of Pd 0 from Pd II by Geobacter sulfurreducens was also reported when acetate and AQDS were supplied to the systems as electron donor and RM, respectively [43] .…”

“…These findings correlate well with previous reports in which the reduction of Te IV was studied. The formation of Te precipitates in the cytoplasm of R. capsulatus grown under anaerobic-photosynthetic conditions using pyruvate as the carbon source was observed [29] as well as, the accumulation of Te 0 nanorods in the periphery of B. selenitireducens cultured under anaerobic conditions using lactate as electron donor [24] . In both studies, the formation of extracellular precipitates was also confirmed.…”

Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe)

“…Our results also demonstrated a high tolerance of the methanogenic communities to Se VI . Likewise Te, both Se oxyanions can be reduced to insoluble Se 0 by microbial means (Astratinei et al, 2006; Borghese et al, 2014). The lower bioavailability of soluble Se resulting from the formation of insoluble Se 0 might have improved the tolerance to Se.…”