Pigments and isoprenoid compounds in extremely and moderately halophilic bacteria

Abstract

Quantitative measurements were carried out on pigmented and colorless isoprenoid compounds in several species of extremely and moderately halophilic bacteria. Phytoene was found in most extreme halophiles; it was present in high concentrations in a moderately halophilic coccus (H5) and absent from a moderately halophilic rod (A31C). Only the pigmented extreme halophiles contained β-carotene. Halobacterium cutirubrum contained substantial amounts of lycopene; this compound was present only in small amounts or missing from the other bacteria. Though lycopene is a precursor of β-carotene in plants, there was no correlation between the amounts of lycopene and β-carotene in the different bacterial species. C50 pigments (bacterioruberins) were found only in pigmented extreme halophiles. There was no consistent correlation between the amounts of C40 and C50 compounds in these bacteria. This suggests that the latter may have a biosynthetic pathway independent of the former.Squalene, dihydrosqualene, and tetrahydrosqualene were found in most of the bacteria studied. Menaquinone was found in all species, except the moderately halophilic rod A31C which contained ubiquinone instead. The visual pigment retinal was found in most of the pigmented extreme halophiles, but was not detected in the moderate halophiles.