The major carotenoid pigment of a psychrotrophic Micrococcus roseus strain: purification, structure, and interaction with synthetic membranes

The major carotenoid pigment of a psychrotrophic Micrococcus roseus strain was purified to homogeneity from methanol extracts of dried cells by reverse-phase liquid chromatography and was designated P-3. On the basis of the UV-visible, infrared, mass, and 'H nuclear magnetic resonance spectra of P-3, it was identified as bisdehydro-,-carotene-2-carboxylic acid. The pigment interacted with synthetic membranes of phosphatidyl-choline and dimyristoyl phosphatidylcholine and stabilized the membranes. These results also indicate that P-3 is different from canthaxanthin, the major carotenoid pigment from a mesophilic M. roseus strain. Carotenoid pigments are present in a wide variety of bacteria, algae, fungi, and plants (1, 23). In photosynthetic organisms, carotenoids are closely associated with the pho-tosynthetic membranes, and they help in harvesting and transferring light energy to chlorophyll and also protect the photosynthetic apparatus against photooxidation (34). Caro-tenoid pigments are also present in a wide variety of non-photosynthetic bacteria and serve as an important taxo-nomic marker for the identification of isolates of a particula