Clustering on dinucleotide values. (a) Clustering on dinucleotide abundance values of the genomes of all the organisms under study by city-block (Manhattan) distance. (b) Clustering made by dinucleotide frequencies at the first and second codon positions of genes for all organisms under study. The distance in the clustering is Euclidean distance. Red and blue lines signify halophilic and non-halophilic organisms, respectively. Archaeal species are written in pink and the species adapted to high temperature are underlined. Organism abbreviations are listed in Table 1.