r/K selection of GC content in prokaryotes

Abstract

AbstractThe guanine/cytosine (GC) content of prokaryotic genomes is species‐specific, taking values from 16% to 77%. This diversity of selection for GC content remains contentious. We analyse the correlations between GC content and a range of phenotypic and genotypic data in thousands of prokaryotes. GC content integrates well with these traits into r/K selection theory when phenotypic plasticity is considered. High GC‐content prokaryotes are r‐strategists with cheaper descendants thanks to a lower average amino acid metabolic cost, colonize unstable environments thanks to flagella and a bacillus form and are generalists in terms of resource opportunism and their defence mechanisms. Low GC content prokaryotes are K‐strategists specialized for stable environments that maintain homeostasis via a high‐cost outer cell membrane and endospore formation as a response to nutrient deprivation, and attain a higher nutrient‐to‐biomass yield. The lower proteome cost of high GC content prokaryotes is driven by the association between GC‐rich codons and cheaper amino acids in the genetic code, while the correlation between GC content and genome size may be partly due to functional diversity driven by r/K selection. In all, molecular diversity in the GC content of prokaryotes may be a consequence of ecological r/K selection.