Structure of a novel monocyclic carotenoid, 3″-hydroxy-2′-isopentenylsaproxanthin ((3R,2′S)-2′-(3-hydroxy-3-methylbutyl)-3′, 4′-didehydro-1′, 2′-dihydro-β, ψ-carotene-3, 1′-diol), from a flavobacterium Gillisia limnaea strain DSM 15749

Gillisia limnaea strain DSM 15749 (=R-8282T, =LMG21470,=CIP108418) is a Gram-negative, strictly aerobic, psychrophilic, and non-photosynthetic bacterium that belongs to the family Flavobacteriaceae, which was isolated from a microbial mat in Lake Fryxell, Antarctica ( Van Trappen et al., 2004). The bacterium shows yellow colored colony, but the carotenoid composition has never been determined yet. In this study, we elucidated the structure of carotenoids produced by the strain DSM 15749. G. limnaea strain DSM 15749 synthesized a novel monocyclic-type carotenoid, 3″-hydroxy-2′-isopentenylsaproxanthin ((3R, 2′S)-2′-(3-hydroxy-3-methylbutyl)-3′, 4′-didehydro-1′, 2′-dihydro-β, ψ-carotene-3, 1′-diol), as well as (3R, 3′R)-zeaxanthin. Furthermore, another monocyclic carotenoid, 2′-isopentenylsaproxanthin, was also detected in the strain DSM 15749. 3″-Hydroxy-2′-isopentenylsaproxanthin is “Chimera”-like unique structures, in that one end group forms the same structure of zeaxanthin, and the other end group is the same as bacterioruberin which is produced by several extremophilic bacteria and archaea. This structure involved the hydroxy derivative of 2′-isopentenylsaproxanthin. The present study is the first report about the carotenoids produced by the genus Gillisia, of the family Flavobacteriaceae.