Table 2.

Association between COGs and descriptive variables.

Functional category	Number of genes analyzed	Bonferroni-corrected P value for one-sided U−test for association between genes in a given COG and(1)
		>nt diversity	>Number of Informative sites	>Codon bias(2)	<Codon bias(2)	>dS	>dN
Energy production and conversion	85						<0.001
Nucleotide metabolism and transport	37					0.03
Translation, ribosomal structure, and biogenesis	110			<0.001		0.03
Replication, recombination, and repair	70	<0.001	<0.001				0.03
Cell wall/membrane/envelope biogenesis	75					0.002
Function unknown	93				0.023		0.03
Intracellular trafficking, secretion and vesicular transport	29				0.020	0.039
Not in COGs	47				0.040		<0.001

⁽¹⁾“>” or “<” indicates the direction of the one-sided tests (i.e. “>Codon bias” shows Bonferroni-corrected P-values for associations between genes in a given COG and higher codon bias as compared to the genes in other COGs, and “<Codon bias” represents a contrast tendency).

⁽²⁾Tests for codon bias were performed using N_c values (a lower N_c means increased codon bias).