Conservation of gene order amongst cell wall and cell division genes in Eubacteria, and ribosomal genes in Eubacteria and Eukaryotic organelles

Comparison of genome sequences from Eubacteria and Eukaryotic organelles sh ows that the order of genes in gene clusters encoding certain highly conser ved cell division proteins and ribosomal proteins is itself highly conserve d. Experiments with a cluster of cell division and related genes of E. coli have shown that this gene order is not essential for function. Comparisons between genomes also show that no pair of genes are necessarily adjacent i n all genomes. The reason for the extreme conservation of order is therefor e unknown, although one possible explanation might be the lateral exchange of tightly-linked groups of genes coding for co-adapted sets of proteins.