Ancient bacteria liked it hot

Abstract

Proteins from ancestral bacteria have been modelled and reconstructed. Strikingly, the heat stability of these proteins parallels the temperatures of their ocean habitats, as determined from the geological record. Comparisons of genome sequence data in closely and distantly related modern organisms can be used for the computational reconstruction of ancient protein sequences that may have existed in related but now extinct types. These proteins can then be 'resurrected' in the laboratory. This has now been achieved for a group of 25 ancestral elongation factors from bacteria across an estimated span of 3 billion years. These ancient proteins display a near linear increase in thermostability travelling back in geological time, suggesting that the environment supporting ancient life was initially hot, then cooled progressively by about 30 °C during that period. This pattern is corroborated by the palaeotemperature trend inferred for the geologic record.