Gene order in Prokaryotes: conservation and implications

Abstract

Genes in Prokaryotes are often organised in operons, groups of contiguous genes that function as single transcription units, or clusters, groups of contiguous genes subject to complex regulation that code for several transcripts. Several models suggest that the grouping of genes in operons or clusters provides physiological and genetic advantages that positively select their formation and maintenance. However, gene order along the chromosome is an evolutionary trait that is lost relatively quickly, since frequent chromosomal reorganisations and acquisition of foreign DNA shuffle the genetic material. As result, operons are generally conserved only among closely related species and widely conserved operons are scarce, although gene neighbourhood may be a more conserved property. Interestingly, the conservation of operons, gene clusters or neighbourhoods can be used as indicator of functional relations between gene products.