Fig.1. Dependence of alanine (A) and lysine (B) contents on GC content of a gene. The amino acid contents were analyzed by using 7 microbial (5 eubacteria and 2 archaea) genome data (Mycobacterium tuberculosis (65.6), Aeropyrum pernix (56.3), Escherichia coli (50.8), Bacillus subtilis (43.5), Haemophilus influenzae (38.1), Methanococcus genitarium (31.3) and Borrelia burgdorferi (28.2); numbers in the parentheses indicate average GC contents of the microbial genomes). Dependence of other 18 amino acid contents on GC content of a gene were obtained by the similar procedures described in this figure (data not shown).