Biosynthesis of carotenoid glucoside esters in Myxococcus fulvus (Myxobacterales): Inhibition by nicotine and carotenoid turnover

Abstract

1. 1. The inhibitory effects of nicotine at various concentrations (0,02 to 8.00 mM) on carotenogenesis in Myxococcus fulvus were investigated. 2. 2. Nicotine inhibited the cyclization of carotenoid glucoside esters at low concentration (<1 mM). A new acyclic carotenoid glucoside ester accumulated. When the inhibitor was removed, a monocyclic carbonylated glucoside ester was synthesized at the expense of the acyclic glucoside ester. 3. 3. A second intermediate, a monocyclic non-carbonylated glucoside ester, was accumulated when cells were reincubated anaerobically after removal of nicotine. Further aerobic incubation resulted in the carbonylation of this monocyclic intermediate. 4. 4. At higher concentration (>1 mM), nicotine inhibited the introduction of the hydroxyl group at 1' position of carotenes (inhibition of hydration across the 1',2'-double bond). Lycopene accumulated under such conditions. 5. 5. Three further effects of nicotine on cell growth are discussed. 6. 6. Virtually no turnover or degradation of carotenoids were found during a time range of 22 h (about four generation times).