Some microorganisms like it hot. Be it the toasty springs at Yellowstone National Park or the infernal environs of deep-sea hydrothermal vents, these so-called thermophiles require heat in order to survive. Their extreme needs captivate scientists, who marvel at their biochemistry, ponder their evolutionary significance and imagine their biotechnological potential. Aiming to better understand these strange microbes, investigators have increasingly turned to genome sequencing. The latest genetic secrets, coming from a heat- and acid-loving organism dubbed Thermoplasma acidophilum, are revealed in today's issue of the journal Nature.
The decoding of T. acidophilum's genome, which at a mere 1.5 million base pairs is among the smallest unraveled to date, has yielded some surprises. Of particular interest is the fact that T. acidophilum sports a number of genes that it appears to have snagged from other species: 17 percent of its "open-reading frames" (protein-encoding regions of the genome) have relatives in the genome of a bacterium known as Sulfolobus solfataricus. In a commentary accompanying the Nature report, Don Cowan of University College London surmised that several factors might have contributed to T. acidophilum's propensity for gene aquisition, including its lack of a protective cell wall to prevent entry of large molecules into the cell.
The new results also speak against a theory put forth by evolutionary biologists. Noting the similarities between this microorganism and the eukaryotic cells that make up higher organisms, researchers had proposed that T. acidophilum was an ancestor to the eukaryotic cell. The new study, however, reveals that T. acidophilum's genes are more similar to bacterial genes. Obvious progress notwithstanding, Cowan concludes that scientists still have a long way to go in terms of understanding gene function in general. "As yet, we do not know what 45 percent of the protein-coding regions in T. acidophilum do," he notes. "That is a lot of genes."