Open AccessThe terminal reductases for selenate and nitrate respiration in Thauera selenatis are two distinct enzymes
Author(s) -
Sabine Rech,
Joan M. Macy
Publication year - 1992
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.174.22.7316-7320.1992
Subject(s) - selenate , periplasmic space , nitrate reductase , biology , electron acceptor , biochemistry , mutant , nitrate , electron transport chain , enzyme , electron donor , microbiology and biotechnology , escherichia coli , chemistry , selenium , ecology , organic chemistry , gene , catalysis
A number of approaches have been used to show that a recently isolated selenate-respiring bacterium, Thauera selenatis, is able to synthesize both a selenate reductase (SR) and a nitrate reductase (NR). (i) The pH optimum of the SR was found to be 6.0; that of the NR was 7.0. (ii) The presence of nitrate did not inhibit selenate reduction in selenate-grown cells. (iii) In cell extracts, the highest SR or NR activity was observed in cells grown with the respective electron acceptor. (iv) Mutants that were unable to grow with nitrate as the terminal electron acceptor and lacked NR activity were isolated; these mutants grew normally with selenate and synthesized SR. (v) The SR was found in the periplasmic space of the cell, whereas the NR was present in the cytoplasmic membrane. A hypothetical electron transport system involving the SR is described.