Molecular evolution of protein atomic composition

Living organisms encounter various growth conditions in their habitats, rai sing the question of whether ecological fluctuations could alter biological macromolecules. The advent of complete genome sequences and the characteri zation of whole metabolic pathways allowed us to search for such ecological imprints. Significant correlations between atomic composition and metaboli c function were found in sulfur- and carbon-assimilatory enzymes, which app ear depleted in sulfur and carbon, respectively, in both the bacterium Esch erichia coli and the eukaryote Saccharomyces cerevisiae, In addition to gen etic instructions, genomic data thus also provide paleontological records o f environmental nutrient availability and of metabolic costs.