Two fundamentally different classes of microbial genes | Semantic Scholar

Nearly all bacterial and archaeal chromosomes were found to encompass large segments of 100-300 kilobases that were significantly enriched in either ancient or young genes, suggesting long-range gene clustering in prokaryotic chromosomes reflects perpetual genome rearrangement driven by a combination of selective and neutral processes rather than evolutionary conservation.

A mathematical model of microbial evolution is developed and tested against extensive data from multiple genome comparisons to indicate that genome evolution is not governed by streamlining but rather, reflects the balance between the benefit of additional genes that diminishes with the genome size and the intrinsic preference for DNA deletion over acquisition.