Table 5. The number and percentage of genes on essential and dispensable chromosomes encoding signal peptides and non-signal peptides and the average Ka and Ks values for the two groups of genes on essential and dispensable chromosomes.

	signal peptide (HMM>0.9)				Non signal peptide
	No of genes	Ka	Ks	Ka/Ks	No of genes	Ka	Ks	Ka/Ks
Essential chromosomes	770	0.026	0.188	0.168	9510	0.0216	0.184	0.138
	7.5%				92.5%
Dispensable chromosomes	17	0.036	0.048	0.378	637	0.057	0.102	0.741
	2.5%				97.5%