ISOLATION OF THE FLAGELLAR SWELLING AND IDENTIFICATION OF RETINAL IN THE PHOTOTACTIC FLAGELLATE, OCHROMONAS-DANICA (CHRYSOPHYCEAE)

Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate al ga has a swelling near the base of the short flagellum and a chloropla stidic stigma in close association with it. A procedure is described f or the isolation of this three dimensional flagellar swelling, the pre sumed photoreceptor. In contrast to an earlier method developed for th e isolation of the paraflagellar swelling from Euglena gracilis, the p rotocol reported here for Ochromonas results in higher yields that sho uld facilitate future biochemical investigations and could open avenue s of investigation for the isolation and purification of the presumpti ve receptor protein. To verify the hypothesis that a rhodopsin-like pr otein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Och romonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may sugges t that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment.