Inhibitory effects of myxothiazol and 2-n-heptyl-4-hydroxyquinoline-N-oxide on the auxiliary electron transport pathways of Rhodobacter capsulatus

D. J. Richardson, D. J. Kelly, J. B. Jackson, S. J. Ferguson, K. Alef

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The effects of various electron transport inhibitors upon the rates of reduction NO3-, dimethyl sulphoxide (DMSO) and N2O in anaerobic suspensions of Rhodobacter capsulatus have been studied. A new method for the determination of the rates of reduction of these auxiliary oxidants in intact cells is presented, based on the proportionality observed between the concentration of oxidant and the duration of the electrochromic carotenoid bandshift. For NO3-and N2O good agreement was found between rates of reduction determined using electrodes and those determined by the electrochromic method. Myxothiazol and antimycin A had no effect on the rates of reduction of NO3-and DMSO suggesting that the cytochrome b/c1complex is not involved in electron transport to these oxidants. 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) inhibited at two sites, one within the cytochrome b/c1complex and the other on the nitrate reducing pathay, but had no effect on electron transport to N2O or DMSO. In both intact cells and cell free extracts, HOQNO had no effect on the nitrate dependent re-oxidation of reduced methylviologen (MVH2), a direct electron donor to nitrate reductase. Our data are consistent with a branch point for the auxiliary electron transport pathways at the level of the ubiquinone pool.

Original languageEnglish
Pages (from-to)159-165
Number of pages7
JournalArchives of Microbiology
Issue number2
Publication statusPublished - Nov 1986


  • 2-n-heptyl-4-hydroxyquinoline-N-oxide
  • Auxiliary electron transport
  • Myxothiazol
  • Nitrate reduction
  • Rhodobacter capsulatus
  • Ubiquinone pool

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