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  • 1
    Electronic Resource
    Electronic Resource
    The electron transport system of Alcaligenes eutrophus H16 (1991)
    Springer
    Archives of microbiology 155 (1991), S. 382-390 
    Details
    ISSN: 1432-072X
    Keywords: Alcaligenes eutrophus H16 ; Paracoccus denitrificans ; Electron transport system ; Cytochrome composition ; Ubiquinol-cytochrome c oxidoreductase ; Terminal oxidases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The electron transport system of autotrophically grown Alcaligenes eutrophus H16 has been investigated by spectroscopic and thermodynamic approaches. The results have been interpreted as evidence that isolated membranes contain a branched respiratory chain composed of three c-type haems (E m,7=+160 mV, + 170 mV, and + 335 mV), five b-type haems (E m,7=+ 5 mV, + 75 mV, + 205 mV, + 300 mV, and + 405 mV), two (possibly three) a-type haems [E m,7= + 255 mV, + 350 mV, (+ 420 mV)], and nne d-type haem. EPR-analysis of the signals at g=1.93, g=2.02, and g=1.90 revealed the presence of iron-sulphur centres diagnostic of complexes I (NADH dehydrogenase), II (succinate dehydrogenase), and III (ubiquinol/cytochrome c oxidoreductase). The low potential b haems (+ 5 mV and + 75 mV) plus the Rieske protein (g=1.90, E m,7=+ 280 mV), thought to be part of an orthodox bc 1 complex, were present in low amounts as compared to their counterparts in membranes from Paracoccus denitrificans. CO-difference spectra in the presence of either succinate, NADH, hydrogen, ascorbate/TMPD, and/or dithionite as reductants, suggested the existance of four different oxidases composed by bo-, cb-, a-, and d-type haems. It is concluded that in contrast to other chemolithotrophes, e.g. P. denitrificans, autotrophic growth of Alcaligenes eutrophus utilizes a respiratory system in which the bc 1 complex containing pathway is only partially involved in electron transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243459
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  • 2
    Electronic Resource
    Electronic Resource
    The electron transport system of Alcaligenes eutrophus H16 (1991)
    Springer
    Archives of microbiology 155 (1991), S. 436-443 
    Details
    ISSN: 1432-072X
    Keywords: Alcaligenes eutrophus H16 ; Electron transport system ; Cytochrome c defective mutant RK1 ; Paracoccus denitrificans ; Respiratory enzyme activities ; Oxidases ; Dehydrogenases ; Myxothiazol ; Antimycin A ; Cyanide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a previous work (Kömen et al. 1991) it has been concluded that membrane fragments isolated from autotrophically grown Alcaligenes eutrophus H16 contain several iron-sulphur centres along with haems of a-, b-, c-, and d-type. These redox components have been proposed to be part of a branched respiratory chain leading to multiple membrane bound oxidases. Here, some of the respiratory activities catalyzed by membrane fragments from wild type cells of A. eutrophus (H16) and, for comparison, Paracoccus denitrificans, have been investigated through the use of electron transport inhibitors. Cyanide (CN-) titration curves indicated that in A. eutrophus H16 oxidation of succinate and H2 preferentially proceeds via the cytochrome c oxidase(s) branch (I 50=2 · 10-5 M) whereas the NADH dependent respiration started being inhibited at higher CN- concentrations (I 50=5 · 10-4 M). In membranes isolated from both, cells harvested at late growth-phase (OD 12) and from a mutant deficient in cytochrome c oxidase activity (A. eutrophus RK1), respiration was insensitive to low CN- concentrations (〈 10-4 M), and it was sustained by the high catalytic activities of two quinol oxidases. These alternative oxidases of b- (formally o-) and d-type showed different sensitivities to KCN (I 50=10-3 M and 10-2 M, respectively). Interestingly, the cytochrome c oxidase(s) dependent respiration of H16 membranes was insensitive to antimycin A but largely inhibited by myxothiazol (10-6 M). This, and previous work (Kömen et al. 1991), suggest that although the respiratory chain of A. eutrophus is endowed with a putative bc 1 complex, its biochemical nature and role in respiration of this organism are apparently different from those of P. denitrificans. The peculiarity of the respiratory chain of A. eutrophus is confirmed by the rotenone insensitivity of the NADH oxidation in both protoplasts and membrane fragments from wild type and soluble hydrogenase deficient cells (HF14 and HF160). A tentative model of the respiratory chain of autotrophically grown A. eutrophus is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00244958
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