PMC

(A) Silver-stained sodium dodecyl sulfate-polyacrylamide gel. Lane 1, periplasmic extract of R. sphaeroides (8 μg of protein); lane 2, His-tagged purified Nap (0.5 μg of protein). MW, molecular weight. (B) Nondenaturing electrophoresis of His-tagged purified Nap. Gels were stained for reductase activity with dithionite-reduced methyl viologen. Lane 1, nitrate reductase activity (1 μg of protein); lane 2, tellurite reductase activity (25 μg of protein); lane 3, selenate reductase activity (25 μg of protein); lane 4, gel stained with Coomassie brillant blue (5 μg of protein).

Oxidation-reduction levels of cytochromes of the c (circles) and b (squares) types in membranes from R. capsulatus MT1131 under NADH-dependent steady-state respiration as a function of time in the absence (open symbols) or presence (closed symbols) of tellurite. Additions of tellurite (2.5 mM) and cyanide (0.05 mM) are indicated by vertical arrows. Values were calculated by assuming the 100% reduction signals at 551 to 540 nm (Cyt c) and 561 to 575 nm (Cyt b) to be those obtained by adding a few crystals of sodium dithionite in a parallel assay and in the absence of tellurite. The data points represent averages of three different membrane preparations.

Resistance of model strains cultured in the absence of tellurite to various concentrations of sodium tellurite on LB-marine plates. Approximately 200 CFU were seeded onto each plate, and the viable population observed on LB-marine plates without tellurite was defined as 100% viability. (A) Cluster 1 strains 1A, 13B, and 30B. (B) Cluster 2 strains 6A and 28A. (C) Cluster 3 strain 14B. Symbols for each strain are noted in the figure. Data points are the average of the results for two independent experiments for each strain.

Light emission from strain LF20116 in the presence of sodium selenite at 0, 0.1, 1.0, 2.5, 5.0, 10.0, or 20.0 μg/ml (A) or sodium tellurite at 0, 0.01, 0.05, 0.1, 0.25, or 0.5 μg/ml (B). Quantification of light emission was performed as described in Materials and Methods. The results shown are the averages of data from three experiments. Standard errors are below 1% and hence are not shown.