Previous Article | Next Article ![]()
J. Bacteriol., 04 1996, 2328-2333, Vol 178, No. 8
W Schumacher and C Holliger
In the anaerobic respiration chain of "Dehalobacter restrictus," dihydrogen
functioned as the electron donor and tetrachloroethene (PCE) functioned as
the electron acceptor. The hydrogenase faced the periplasm, and the PCE
reductase faced the cytoplasmic side of the membrane. Both activities were
associated with the cytoplasmic membrane. UV spectroscopy showed that
membrane-bound menaquinone (MQ) was reduced by oxidation of H2 and
reoxidized by reduction of PCE, indicating that MQ functions as an electron
mediator. Fast proton liberation (t1/2 = 6 +/- 2 s) during electron
transport from H2 to PCE and to trichloroethene (TCE) after addition of
either PCE or TCE to H2- saturated cells resulted in an extrapolated H+/e-
ratio of 1.25 +/- 0.2. This ratio indicated that besides the formation of
protons upon oxidation of H2, vectorial translocation of protons from the
inside to the outside could also occur. Proton liberation was inhibited by
carbonylcyanide m-chlorophenylhydrazone (CCCP), 2-n-heptyl-4-
hydroxyquinoline N-oxide (HOQNO), and CuCl2. Fast proton liberation with an
H+/e- ratio of 0.65 +/- 0.1 was obtained after addition of the MQ analog
2,3-dimethyl-1,4-naphthoquinone (DMN) as an oxidant pulse. This
acidification was also inhibited by CCCP, HOQNO, and CuCl2. Oxidation of
reduced DMN by PCE was not associated with fast acidification. The results
with DMN indicate that the consumption and release of protons associated
with redox reactions of MQ during electron transfer from H2 to PCE both
occurred at the cytoplasmic side of the membrane. The PCE reductase was
photoreversibly inactivated by 1- iodopropane, indicating that a corrinoid
was involved in the PCE reduction.
Copyright © 1996, American Society for Microbiology
The proton/electron ration of the menaquinone-dependent electron transport from dihydrogen to tetrachloroethene in "Dehalobacter restrictus"
Limnological Research Center, Swiss Federal Institute for Environmental Science and Technology, Kastanienbaum, Switzerland.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»