Bacterial Carotenoids. X. On the Constitution of the Minor Carotenoids of Rhodopseudomonas. 1. P518.

Abstract
A new bacterial carotenoid, (provisionally termed P518) isolated from a tan mutant and the wild-type of R. spheroides exhibits absorption maxima in visible light at longer wave-lengths than any other carotenoid hitherto described. The evidence suggests that the structure is 2-keto-spirilloxanthin (III).