A un-rooted maximum likelihood tree of our BCH database and some other BCHs from bacteria, higher plants and cyanobacteria. The sequences information of BCH from cyanobacteria, bacteria and higher plants was downloaded from Cyanobase or NCBI database respectively and summarized in an additional file [see Additional file 3: Table S2]. A partial protein sequence (position: 110–400) has been selected for phylogenetic analysis. A maximum likelihood phylogenetic tree (loglk = −12176.58485) as inferred from amino acid sequences (291 amino acid characters) of BCH and CrtR proteins was computed using LG model for amino acid substitution (selected by PROTTEST) with discrete gamma distribution in four categories. All parameters (gamma shape = 1.963; proportion of invariants = 0.010; number of categories: 4) were estimated from the dataset. Numbers above branches indicate ML bootstrap supports. ML bootstraps were computed using the above mentioned model in 300 replicates. Stars indicate where later gene duplications led to creation of paralogs genes found within one species. Major groups of organisms are labeled to allow comparison between the phylogeny of BCH and algae evolution.