Grouping of halophiles and non-halophiles according to their standardized amino acid usage. Standardized amino acid composition of halophiles and non-halophiles grouped by unweighted pair group average clustering. The left panel depicts the unweighted pair group average clustering on the relative abundances of different amino acid residues in the encoded proteins of organisms with respect to those of E. coli. The distance in the clustering is Euclidean distance. The right panel is a pictorial representation of relative amino acid usage in the respective organisms. The over-representation or under-representation of amino acid residues in the organisms are shown in green and red colored blocks, respectively. Archaeal species are denoted in pink color and the species adapted to high temperature (optimum growth temperature ≥ 65°C) are underlined. Organism abbreviations are listed in Table 1.