Cytochrome d but not cytochrome o rescues the toluidine blue growth sensitivity of arc mutants of Escherichia coli.

The Arc (anoxic redox control) two-component signal transduction system, consisting of the ArcB sensor kinase and the ArcA response regulator, allows adaptive responses of Escherichia coli to changes of O(2) availability. The arcA gene was previously known as the dye gene because null mutants were growth sensitive to the photosensitizer redox dyes toluidine blue and methylene blue, a phenotype whose molecular basis still remains elusive. In this study we report that the toluidine blue O (TBO) effect on the arc mutants is light independent and observed only during aerobic growth conditions.

Cyanide-resistant respiration in Taenia crassiceps metacestode (cysticerci) is explained by the H2O2-producing side-reaction of respiratory complex I with O2.

The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mitochondrial respiration with NADH as substrate was partially inhibited by rotenone, cyanide and antimycin in decreasing order of effectiveness. In contrast, respiration with succinate or ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was more sensitive to antimycin and cyanide.

Flavohemoglobin Hmp, but not its individual domains, confers protection from respiratory inhibition by nitric oxide in Escherichia coli.

Escherichia coli possesses a two-domain flavohemoglobin, Hmp, implicated in nitric oxide (NO) detoxification. To determine the contribution of each domain of Hmp toward NO detoxification, we genetically engineered the Hmp protein and separately expressed the heme (HD) and the flavin (FD) domains in a defined hmp mutant. Expression of each domain was confirmed by Western blot analysis.

The aerobic electron transport system of Eikenella corrodens.

The respiratory system of the fastidious beta-proteobacterium Eikenella corrodens grown with limited oxygen was studied. Membranes showed the highest oxidase activity with ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) or succinate and the lowest activity with NADH and formate. The presence of a bc1-type complex was suggested by the inhibition exerted by 2-heptyl-4-hydroxyquinoline-N-oxide (HOQNO), myxothiazol, and antimycin A on respiration with succinate and by the effect of the latter two inhibitors on the succinate-reduced difference spectra.

Taenia crassiceps metacestodes have cytochrome oxidase aa3 but not cytochrome o functioning as terminal oxidase.

In mitochondria obtained from Taenia crassiceps metacestodes, carbon monoxide difference spectra reveal signals characteristic of the classical mitochondrial oxidase, cytochrome aa3, as well as signals suggesting the presence of 'cytochrome o'. In the present work, using photodissociation spectrophotometry and analysis of the haem groups, we conclude that there is no haem O in these larvae, and that the only cytochrome that functions as terminal oxidase is cytochrome c oxidase, aa3. At temperatures between -70 and -100 degrees C, the energy of activation for CO reassociation with cytochrome a3 was 10.

An unusual cytochrome o'-type cytochrome c oxidase in a Bacillus cereus cytochrome a3 mutant has a very high affinity for oxygen.

Bacillus cereus strain PYM1 is a mutant unable to synthesize haem A or spectrally detectable cytochromes aa3 or caa3. The nature of the remaining oxidase(s) catalysing oxygen uptake has been studied. Respiratory oxidase activities and the levels of cytochromes b and c increased 2.