Spectroscopic and potentiometric characterization of cytochromes in two Sporomusa species and their expression during growth on selected substrates |
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Authors: | Beate Kamlage Andreas Boelter Michael Blaut |
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Institution: | (1) Institut für Mikrobiologie der Universität Göttingen, Grisebachstrasse 8, W-3400 Göttingen, Federal Republic of Germany |
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Abstract: | The homoacetogenic bacteria Sporomusa ovata and Sporomusa sphaeroides were grown on betaine, betaine + formate, and acetoin in the absence of carbon dioxide, and the formation of membrane-bound cytochromes was determined. In S. sphaeroides, the growth substrate had little influence on the expression of cytochromes. In contrast, membranes from betaine-or acetoin-grown S. ovata cells had an 11-or 3-fold higher cytochrome b content than cells grown on betaine + formate. The cytochrome c content was reduced below the detection level after growth on the latter two substrates. The cytochromes in the membranes of S. sphaeroides and S. ovata were characterized by low-temperature difference spectroscopy, hemochrome difference spectroscopy, and redox potentiometry. Membranes of S. ovata were shown to contain two b-type cytochromes with Em,7=-153±10 mV and Em,7=-226±14 mV and two c-type cytochromes with Em,7=-86±6 mV and Em,7=-265±10 mV. In S. sphaeroides also two b-type cytochromes with Em,7=-165±7 mV and Em,7=-241±2 mV and two c-type cytochromes with Em,7=-101±4 mV and Em, 8.5=-338±9 mV could be distinguished. Cell extracts of S. sphaeroides were shown to contain all the enzymes of the acetyl-CoA (Wood) pathway. The degradation pathways of the substrates tested and the possible role of the cytochromes are discussed.Abbreviations Em,7
midpoint potential at pH 7 and 25°C
- H4F
tetrahydrofolate |
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Keywords: | Cytochromes Redox difference spectroscopy Midpoint potential Betaine Formate Acetoin Acetyl-CoA pathway Sporomusa ovata Sporomusa sphaeroides |
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