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Ferrous iron oxidation in moderately thermophilic acidophile Sulfobacillus sibiricus N1T

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Abstract:

The iron-oxidizing system of a moderately thermophilic, extremely acidophilic, gram-positive mixotroph, Sulfobacillus sibiricus N1T, was studied by spectroscopic, high-performance liquid chromatography and inhibitory analyses. Hemes B, A, and O were detected in membranes of S. sibiricus N1T. It is proposed that the electron transport chain from Fe2+ to O2 is terminated by 2 physiological oxidases: aa3-type cytochrome, which dominates in the early-exponential phase of growth, and bo3-type cytochrome, whose role in iron oxidation becomes more prominent upon growth of the culture. Both oxidases were sensitive to cyanide and azide. Cytochrome aa3 was more sensitive to cyanide and azide, with Ki values of 4.1 and 2.5 µmol·L-1, respectively, compared with Ki values for cytochrome bo3, which were 9.5 µmol·L-1 for cyanide and 7.0 µmol·L-1 for azide. This is the first evidence for the participation of a bo3-type oxidase in ferrous iron oxidation. The respiratory chain of the mixotroph contains, in addition to the 2 terminal oxidases, a membrane-bound cytochrome b573.

Le système d’oxydation du fer de Sulfobacillus sibiricus N1T, une bactérie mixotrophe positive à Gram modérément thermophile et extrêmement acidophile, a été étudié par spectroscopie, chromatographie liquide à haute performance et par des analyses d’inhibition. Les hèmes B, A et O ont été détectés dans les membranes de S. sibiricus N1T. Il est proposé que la chaine de transport d’électrons du Fe2+ au O2 se termine par 2 oxydases : un cytochrome du type aa3, qui domine lors de la phase exponentielle de croissance, et un cytochrome du type bo3, dont le rôle dans l’oxydation du fer augmente en fonction de la croissance de la culture. Les 2 oxydases étaient sensibles au cyanure et à l’azide. Le cytochrome aa3 était plus sensible au cyanure et à l’azide, avec des valeurs respectives de Ki de 4,1 et de 2,5 µmol·L-1 comparativement aux valeurs de Ki du cytochrome bo3 qui étaient de 9,5 µmol·L-1 pour le cyanure et de 7,0 µmol·L-1 pour l’azide. Il s’agit de la première preuve de la participation d’une oxydase du type bo3 dans l’oxydation du fer ferreux. La chaine respiratoire du mixotrophe contient, outre les 2 oxydases terminales, le cytochrome b573 lié à la membrane.

Document Type: Research Article

Publication date: October 1, 2010

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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