HALORHODOPSIN and PHOTOSENSORY BEHAVIOR INHalobacterium halobiumMUTANT STRAIN L‐33

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Abstract
Halobacterium halobium, strain L‐33, which is deficient in bacteriorhodopsin (BR) but synthesizes increased amounts of halorhodopsin (HR), shows behavioral responses upon changes in fluence rate with visible light or with UV light. The observations support the earlier report (Schimzet al., 1982). that BR is not essential for photosensing inH. halobium.In the UV‐range, changes in light intensity elicit the maximal response at λ= 370 nm. In the visible range, changes in light intensity show the maximal response at Δ= 565 nm and a secondary peak at Δ= 590 nm. The latter corresponds to the absorption maximum of HR (Δmax= 588 nm). This light‐energy converting retinal pigment ofH. halobiumthus appears to contribute to photosensory behavior.