PHOTOSYNTHESIS AND PHOTORECEPTION IN HALO BACTERIA

The photobiology of Halobacteria is reviewed here. Furthermore, the fu nctions of halobacterial retinal proteins as ion pumps for photosynthe sis and as sensors mediating phototaxis are described. The well-charac terized transport mechanism of bacteriorhodopsin allows the suggestion of a general functional model of all halobacterial retinal proteins d ue to their structural similarities. Experimental findings showing the respective interconversions of proton- and chloride (halide)-pumps, o f outward-directed to inward-directed pumps and of sensors to pumps co nfirm this model. From these findings a general concept of ion translo cation is derived and described as the ''IST'' model.