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Inferring the palaeoenvironment of ancient bacteria on the basis of resurrected proteinsFeatures of the physical environment surrounding an ancestral organism can be inferred by reconstructing sequences of ancient proteins made by those organisms, resurrecting these proteins in the laboratory, and measuring their properties. Here, we resurrect candidate sequences for elongation factors of the Tu family (EF-Tu) found at ancient nodes in the bacterial evolutionary tree, and measure their activities as a function of temperature. The ancient EF-Tu proteins have temperature optima of 55-65 degrees C. This value seems to be robust with respect to uncertainties in the ancestral reconstruction. This suggests that the ancient bacteria that hosted these particular genes were thermophiles, and neither hyperthermophiles nor mesophiles. This conclusion can be compared and contrasted with inferences drawn from an analysis of the lengths of branches in trees joining proteins from contemporary bacteria, the distribution of thermophily in derived bacterial lineages, the inferred G + C content of ancient ribosomal RNA, and the geological record combined with assumptions concerning molecular clocks. The study illustrates the use of experimental palaeobiochemistry and assumptions about deep phylogenetic relationships between bacteria to explore the character of ancient life.
Document ID
20040096213
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Gaucher, Eric A. (NASA Headquarters Washington, DC United States)
Thomson, J. Michael
Burgan, Michelle F.
Benner, Steven A.
Date Acquired
August 21, 2013
Publication Date
September 18, 2003
Publication Information
Publication: Nature
Volume: 425
Issue: 6955
ISSN: 0028-0836
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other