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Differential expression of two bc 1 complexes in the strict acidophilic chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans suggests a model for their respective roles in iron or sulfur oxidation. Microbiology 153: 102-110

University of Santiago, Chile, CiudadSantiago, Santiago Metropolitan, Chile
Microbiology (Impact Factor: 2.56). 02/2007; 153(Pt 1):102-10. DOI: 10.1099/mic.0.2006/000067-0
Source: PubMed

ABSTRACT

Three strains of the strict acidophilic chemolithoautotrophic Acidithiobacillus ferrooxidans, including the type strain ATCC 23270, contain a petIIABC gene cluster that encodes the three proteins, cytochrome c1, cytochrome b and a Rieske protein, that constitute a bc1 electron-transfer complex. RT-PCR and Northern blotting show that the petIIABC cluster is co-transcribed with cycA, encoding a cytochrome c belonging to the c4 family, sdrA, encoding a putative short-chain dehydrogenase, and hip, encoding a high potential iron-sulfur protein, suggesting that the six genes constitute an operon, termed the petII operon. Previous results indicated that A. ferrooxidans contains a second pet operon, termed the petI operon, which contains a gene cluster that is similarly organized except that it lacks hip. Real-time PCR and Northern blot experiments demonstrate that petI is transcribed mainly in cells grown in medium containing iron, whereas petII is transcribed in cells grown in media containing sulfur or iron. Primer extension experiments revealed possible transcription initiation sites for the petI and petII operons. A model is presented in which petI is proposed to encode the bc1 complex, functioning in the uphill flow of electrons from iron to NAD(P), whereas petII is suggested to be involved in electron transfer from sulfur (or formate) to oxygen (or ferric iron). A. ferrooxidans is the only organism, to date, to exhibit two functional bc1 complexes.

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    • "In contrast to A. ferrooxidans ATCC 23270, which was reported to use an aa 3 -type cytochrome c oxidase as terminal oxi- dase[41,77,85], " Ferrovum " strain JA12 was predicted to reduce oxygen via a cbb 3 -type cytochrome c oxidase similar to the neutrophilic iron oxidisers Mariprofundus ferrooxydans PV-1[82]and S. lithotrophicus ES-1[75]and similar to the acidophiles " F. myxofaciens " P3G[28]and Leptospirillum ferriphilum ML-4[29]. Although only genes predicted to encode the subunits I and II of the cbb 3 -type cytochrome c oxidase were identified in the genome of " Ferrovum " strain JA12, one of the co-localised c-type cytochromes (FERRO_02610, FERRO_02510) could substitute the missing subunit III, which also represents a c-type cyto- chrome[86](S4C Fig).Furthermore, two alternative terminal oxidases were predicted that use quinol as electron donor instead of the soluble c-type cytochromes: the cytochrome bo 3 ubiquinol oxidase and the cytochrome bd complex. " Ferrovum " strain JA12 presumably generates reduction equivalents for biosyntheses similar to A. ferrooxidans transferring electrons from the c-type cytochrome in the periplasm via the bc 1 complex and the quinol pool to the NADH-quinone oxidoreductase complex[41,77,85]. "
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    Full-text · Article · Jan 2016 · PLoS ONE
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    • "These operons are differentially transcribed in response to growth conditions. Namely, bc 1 complex form II encoded by the pet II operon is preferably expressed in S 0 -cells (Bruscella et al. 2007). Part of the pet II operon is a short-chain dehydrogenase/ reductase family protein (SdrA2; spot No. 318, AFE_0377). "
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    • "It was suggested about a decade ago that the cellular ATP/ADP ratio regulates the balance of reducing equivalents from Fe(II), favouring either the activation of the aa3 cytochrome oxidase and thus promote the downhill pathway or, conversely, the repression of the aa3 cytochrome oxidase promoting the use of the uphill pathway (Elbehti et al., 2000). In addition to regulatory decisions regarding the flux of electrons uphill or downhill, At. ferrooxidans also regulates enzymes and electron carriers depending on whether its energetic substrate is Fe(II) or RISCs (Yarzabal et al., 2004; Bruscella et al., 2007; Amouric et al., 2009; Quatrini et al., 2009). "
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