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A nonhyperthermophilic common ancestor to extant life forms
N Galtier1, N Tourasse, M Gouy
1Laboratoire de Biométrie, Génétique et Biologie des Populations, Université C. Bernard Lyon 1, France.
Science (New York, N.Y.)
|January 8, 1999
Summary
Prokaryotic ribosomal RNA (rRNA) G+C content correlates with growth temperature. Analyzing rRNA sequences suggests the earliest life forms may not have thrived in high-temperature environments, challenging origin of life theories.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Astrobiology
Background:
- The G+C nucleotide content in ribosomal RNA (rRNA) sequences of prokaryotes is linked to their optimal growth temperatures.
- This correlation offers a potential method to infer the environmental conditions of early life forms.
Purpose of the Study:
- To estimate the ancestral base composition of the common ancestor of all life.
- To infer the environmental temperature of this common ancestor using rRNA G+C content.
Main Methods:
- Development of a sequence evolution model accounting for lineage-specific G+C content variations and unequal substitution rates.
- Application of the model to rRNA sequences from diverse species representing major life lineages.
Main Results:
- Inferred G+C content of the common ancestor to extant life forms was determined.
- The estimated G+C content suggests an optimal growth temperature incompatible with high-temperature environments.
Conclusions:
- The inferred environmental conditions of the common ancestor challenge the widely accepted hypothesis of life originating in high-temperature settings.
- This study provides new insights into the environmental context of early life on Earth.