text: Archaerhodopsin 1 and 2 (AR1 and AR2) were the first archaerhodopsins to be identified and are expressed by Halobacterium sp. Aus-1 and Aus-2 respectively. Both species were first isolated in Western Australia in the late 1980s. The crystal structures of both proteins were solved by Kunio Ihara, Tsutomo Kouyama and co-workers at Nagoya University, together with collaborators at the Spring-8 synchrotron.