Genus Specific Unusual Carotenoids in Purple Bacteria, Phaeospirillum and Roseospira: Structures and Biosyntheses Shinichi Takaichi • Takashi Maoka • Ch. Sasikala • Ch. V. Ramana • Keizo Shimada Received: 8 April 2011 / Accepted: 19 April 2011 / Published online: 6 May 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Phototrophic bacteria necessarily contain carotenoids for photosynthesis, and a few phototrophic purple bacteria accumulate unusual carotenoids. The carotenoids in the genera Phaeospirillum and Roseospira were identified using spectroscopic methods. All species of the genus Phaeospirillum contained characteristic polar carotenoids in addition to lycopene and hydroxylycopene (rhodopin); hydroxylycopene glucoside, dihydroxylyco- pene, and its mono- and/or diglucosides. From the struc- tures of these carotenoids, their accumulation was suggested to be due to absence of CrtD (acyclic carotenoid C-3,4 desaturase) and to possession of glucosyltransferase. Species of the genus Roseospira have been reported to have unusual absorption spectra in acetone extract, and they were found to accumulate 3,4-didehydrorhodopin as a major carotenoid. This may be due to low activity of CrtF (acyclic 1-hydroxycarotenoid methyltransferase). The study concludes in identifying genus specific unusual carotenoids, which is probably due to characteristic nature of some carotenogenesis enzymes. Introduction Phototrophic purple bacteria necessarily synthesize not only bacteriochlorophyll (BChl) but also carotenoids for photosynthesis. Around 50 different carotenoids are iden- tified in these bacteria, and most of them are acyclic carotenoids, which are distinct from those found in other anoxygenic photosynthetic bacteria (green sulfur bacteria, green filamentous bacteria, and heliobacteria), cyanobac- teria, algae, fungi, higher plants, and non-photosynthetic bacteria [15, 17, 18]. Takaichi [17, 18] has characterized the carotenoids of purple bacteria and suggested diversity of the biosynthetic pathways of these carotenoids. Around half species of purple bacteria produce spirilloxanthin as a major carotenoid and final product of the normal spirillo- xanthin pathway, which is the fundamental pathway. Other species produce many kinds of carotenoids, and this could be explained when one enzyme of the pathway is lacking or is present with reduced or modified activity, the carotenoid composition of the bacterium is expected to change. Some species of purple bacteria produce carotenoid gly- cosides, and a few purple sulfur bacteria produce okenone and R.g.-keto carotenoid by the okenone pathway. Further, some purple bacteria produce (unidentified) polar carotenoids [15, 17, 18]. Rhodospirillum (Rsp.) fulvum and Rhodospirillum molischianum, which had been described more than six decades ago, produced small amount of Electronic supplementary material The online version of this article (doi:10.1007/s00284-011-9941-1) contains supplementary material, which is available to authorized users. S. Takaichi (&) Department of Biology, Nippon Medical School, 297, Kosugi-cho 2, Nakahara, Kawasaki 211-0063, Japan e-mail: takaichi@nms.ac.jp T. Maoka Research Institute for Production Development, 15 Shimogamo Morimoto Cho, Sakyo ku, Kyoto 606 0805, Japan Ch. Sasikala Bacterial Discovery Laboratory, Centre for Environment, JNT University, Hyderabad 500 085, India Ch. V. Ramana Department of Plant Sciences, University of Hyderabad, Hyderabad 500 046, India K. Shimada Department of Biology, Tokyo Metropolitan University, Minami-ohsawa 1-1, Hachioji, Tokyo 192-0397, Japan 123 Curr Microbiol (2011) 63:75–80 DOI 10.1007/s00284-011-9941-1