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Why Genes Evolve Faster On Secondary Chromosomes In Bacteria, Vaughn S. Cooper, Samuel H. Vohr, Sarah C. Wrocklage, Philip J. Hatcher

Molecular, Cellular & Biomedical Sciences

In bacterial genomes composed of more than one chromosome, one replicon is typically larger, harbors more essential genes than the others, and is considered primary. The greater variability of secondary chromosomes among related taxa has led to the theory that they serve as an accessory genome for specific niches or conditions. By this rationale, purifying selection should be weaker on genes on secondary chromosomes because of their reduced necessity or usage. To test this hypothesis we selected bacterial genomes composed of multiple chromosomes from two genera, Burkholderia and Vibrio, and quantified the evolutionary rates (dN and dS) of all orthologs …