Nucleic
Acids Res., 30,
4264-4271
http://nar.oupjournals.org/cgi/content/abstract/30/19/4264
Abstract:
Most of prokaryotic genomes contain only 6-14% non-coding DNA, is there any tendency forcing them? According to the analysis of distances between conserved gene pairs of several prokoryotic genomes, it shows that neither the fraction of non-coding DNA nor inter and intra-operonic distances is dependent on the number of genes or genome size, but these characteristics positively correlate with each other. In other words, these non-coding regions evolve congruently under the pressure of minimizing the amount of non-functionalDNA, that's quite different from what in eukaryotic genomes, and might be a good entry for understanding the reson why they are.
Reference:
Rogozin,I.B.,
Makarova,K.S., Murvai,J., Czabarka,E., Wolf,Y.I.,
Tatusov,R.L., Szekely,L.A. and Koonin,E.V. (2002) Connected gene
neighborhoods in prokaryotic genomes. Nucleic Acids Res., 30,
2212-2223.
Skovgaard,M.,
Jensen,L.J., Brunak,S., Ussery,D. and Krogh,A. (2001)
On the total number of genes and their length distribution in complete
microbial genomes. Trends Genet., 17, 425-428.
Rogozin,I.B.,
Spiridonov,A.M., Sorokin,A.V., Wolf,Y.I., Jordan,I.K.,
Tatusov,R.L. and Koonin,E.V. (2002) Purifying and directional selection
in overlapping prokaryotic genes. Trends Genet., 18,
228±232.
Salgado,H.,
Moreno-Hagelsieb,G., Smith,T.F. and Collado-Vides,J.
(2000) Operons in Escherichia coli: genomic analyses and predictions.
Proc. Natl Acad. Sci. USA, 97, 6652-6657.