The influence of light quality and prey organisms on the amounts of rhodopsins of the dinoflagellate Oxyrrhis marina

The influence of prey organisms and the availability and quality of light on the amounts of rhodopsins of the plesiomorphic dinoflagellate Oxyrrhis marina were investigated. When the prasinophyte Pyramimonas grossii was used as prey organism, no rhodopsin-containing bands were detected by sucrose density gradient centrifugation of Triton X-100 solubilized membrane fractions, and the 25 kDa protein was missing when the bands and the non-solubilized pellet fractions were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis. On the contrary, Oxyrrhis grown on yeast cells under either white, red, green, or blue light, or in complete darkness did not show significant differences with respect to the amounts of rhodopsins when using the absorbance ratio 520 nm: 740 nm as measure. Significant differences in growth, i.e. in final cell densities and total protein concentrations of the harvested cells, were not registered either. In addition, no differences were registered for the Coomassie staining intensities of the 25 kDa protein band when total cell protein fractions, adjusted to equal protein concentrations, were subjected to sodium dodecyl sulfate gel electrophoresis. The results obtained suggest a potentially novel physiological function for Oxyrrhis rhodopsins, namely, acidification of the interior milieu of the food vacuoles.