The Complete Genome Sequence of Clostridium aceticum: a Missing Link between Rnf- and Cytochrome-Containing Autotrophic Acetogens.
Clostridium aceticum was the first isolated autotrophic acetogen, converting CO2 plus H2 or syngas to acetate. Its genome has now been completely sequenced and consists of a 4.2-Mbp chromosome and a small circular plasmid of 5.7 kbp. Sequence analysis revealed major differences from other autotrophic acetogens. C. aceticum contains an Rnf complex for energy conservation (via pumping protons or sodium ions). Such systems have also been found in C. ljungdahlii and Acetobacterium woodii. However, C. aceticum also contains a cytochrome, as does Moorella thermoacetica, which has been proposed to be involved in the generation of a proton gradient. Thus, C. aceticum seems to represent a link between Rnf- and cytochrome-containing autotrophic acetogens. In C. aceticum, however, the cytochrome is probably not involved in an electron transport chain that leads to proton translocation, as no genes for quinone biosynthesis are present in the genome.


OBJECTIVE
Autotrophic acetogenic bacteria are receiving more and more industrial focus, as CO2 plus H2 as well as syngas are interesting new substrates for biotechnological processes. They are both cheap and abundant, and their use, if it results in sustainable products, also leads to reduction of greenhouse gases. Clostridium aceticum can use both gas mixtures, is phylogenetically not closely related to the commonly used species, and may thus become an even more attractive workhorse. In addition, its energy metabolism, which is characterized here, and the ability to synthesize cytochromes might offer new targets for improving the ATP yield by metabolic engineering and thus allow use of C. aceticum for production of compounds by pathways that currently present challenges for energy-limited acetogens.
Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Georg-August University, Göttingen, Germany.
Anja
A
Poehlein
Institut für Mikrobiologie und Biotechnologie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, Germany.
Martin
M
Cebulla
Institut für Mikrobiologie und Biotechnologie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, Germany.
Marcus M
MM
Ilg
Institut für Mikrobiologie und Biotechnologie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, Germany.
Frank R
FR
Bengelsdorf
Institut für Mikrobiologie und Biotechnologie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, Germany.
Bettina
B
Schiel-Bengelsdorf
Genencor Division, Danisco US Inc., Palo Alto, California, USA.
Gregg
G
Whited
Institute of Biology/Microbiology, University of Halle, Halle, Germany.
Jan R
JR
Andreesen
Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Georg-August University, Göttingen, Germany.
Gerhard
G
Gottschalk
Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Georg-August University, Göttingen, Germany.
Rolf
R
Daniel
Institut für Mikrobiologie und Biotechnologie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, Germany peter.duerre@biologie.uni-ulm.de.
Peter
P
Dürre
D002876:Chromosomes, Bacterial; D003013:Clostridium / Q000235:genetics* / Q000302:isolation & purification; D003580:Cytochromes / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics*; D004734:Energy Metabolism; D016680:Genome, Bacterial; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids; D017422:Sequence Analysis, DNA
D003580:Cytochromes; D004269:DNA, Bacterial