Genome-enabled studies of anaerobic, nitrate-dependent oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans

Abstract

Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic (II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying (II) oxidation assays performed with knockout mutants targeting primarily highly expressed or (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of transposon mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process. © 2013 Beller, Zhou, Legler, Chakicherla, Kane, Letain and O'Day.