Complete Genome Sequence of Aquifex aeolicus
Ronald V. SWANSON*
Recombinant BioCatalysis, USA
Aquifex aeolicus is the most thermophilic bacterium known with a growth optimum of 85℃ and a maximum at 95℃. It is able to grow on a simple mixture of hydrogen, oxygen, carbon dioxide, and mineral salts. Despite the complex metabolic machinery necessary to function as a chemolithoautotroph the genome of Aquifex is only one third the size of the E. coli genome. The limited genome size appears to be largely at the expense of metabolic flexibility. The use of oxygen as an electron acceptor is enabled by the presence of a complex respiratory apparatus with a cytochrome bc1 complex as well as the alternative cytochrome bd ubiquinol oxidase system. In addition there are three superoxide dismutases. Although cells display catalase activity, no catalase gene was identified. Several specific of adaptations to thermophily are apparent from the genome including: high G+C content of stable RNAs, two reverse gyrase genes, and a larger relative proprortion of charged amino acids than is found in mesophile genomes. The complete 1,551,335 base pair genome sequence of the circular chromosome has been determined as well as the sequence of a 39,456 bp circular cryptic extracromosomal element. This is the first complete sequence of a hyperthermopilic bacterium.
