Breakdown of the genes from two eukaryotes by the putative evolutionary affinities. (a) Yeast and (b) red algae. The putative origin of genes was tentatively inferred from the best hits obtained by searching the NCBI non-redundant protein sequence database using the BLASTP program , with all protein sequences from the respective organisms used as queries. Although sequence similarity searches are often regarded as a very rough approximation of the phylogenetic position , the previous analysis of the yeast genome showed a high level of congruence between the best hits and phylogenomic results . Major archaeal and bacterial groups are color-coded and denoted 1 to 18; the number of proteins with the best hit to the given groups is indicated. The groups are: 1, Euryarchaeota; 2, Crenarchaeota-Thaumarchaeota-Nanoarchaeota; 3, Firmicutes; 4, γ-Proteobacteria; 5, α-Proteobacteria; 6, δ- and ε-Proteobacteria; 7, β-Proteobacteria; 8, unclassified Proteobacteria; 9, Cyanobacteria; 10, Actinobacteria; 11, Bacteroides-Chlorobi group; 12, Chloroflexi; 13, Planctomycetes; 14, Verrucomicrobia-Chlamydiae-Spirochetes; 15, Deinococcus-Thermus group; 16, Aquificacae and Thermotogae; 17, other bacteria; 18, no archaeal or bacterial homologs.