At the crossroads between microbiology and optogenetics: rhodopsin channels from unicellular eukaryotes and their viruses

Many unicellular eukaryotes use diverse rhodopsin proteins to sense light. Microbial rhodopsins are seven- or eight-transmembrane-domain proteins with retinal chromophores and are structurally similar to the rhodopsins involved in vision in animals. Since the discovery of channelrhodopsins in unicellular algae, they have been adopted as light-activated regulators of neuronal activity in optogenetics. Analyzing rhodopsin genes from unicellular microbes proved to be a very rewarding strategy of discovering new rhodopsin channels to fulfill the constant demand for rhodopsins with novel electrophysiological properties. By harnessing omics data, we made several unanticipated discoveries of channelrhodopsins and other rhodopsin channels from diverse photosynthetic and heterotrophic unicellular microbes and giant viruses infecting them that have been characterized biophysically with the help of our collaborators.