Characterization of Heumann's pigmented and non-pigmented strains of [Pseudomonas] Sphingomonas echinoides

The objective of this study was to characterize two strains of Sphingomonas echinoides, one of which (B-3126) forms yellow colonies, while the other (B-3127) forms off-white colonies. The total pigments from the two strains were extracted using ethanol:hexane (1:2) and analyzed. Whereas strain B-3126 showed spectra characteristic of carotenoid-producing Sphingomonas spp., strain B-3127 showed spectra characteristic of phytoene, which is a colorless compound. Furthermore, strain B-3126 survived exposure to UV radiation (302 nm for 5-20 s) or H2O2 (5 mM for 1-7 min) much better than strain B-3127. Sequence comparisons indicated that the crt locus of strain B-3127 differed from that of strain B-3126 at only three positions/nucleotides. It remains to be investigated whether these differences contribute to the lack of phytoene desaturase activity in strain B-3127.