FIGURE 1.

Phylogenetic relationships of microbial rhodopsins. A, unrooted tree of microbial rhodopsins showing their functional diversity. The representative ion pumps are shown with the circles. Green is the clade consisting of the MrHR homologues. NpHR, HR from Natronomonas pharaonis. B, phylogenetic tree of the MrHR homologues. Their NCBI accession IDs are indicated in the parentheses. The strains labeled with closed circles also contain the Anabaena sensory rhodopsin gene. Other symbols indicate the cyanobacteria orders and the sources of the host strains. In both trees, nodes with <50% bootstrap percentages are collapsed.