Anti-Obesity Effect of Red Radish Coral Sprout Extract by Inhibited Triglyceride Accumulation in a Microbial Evaluation System and in High-Fat Diet-Induced Obese Mice.

Rhodosporidium toruloides, an oleaginous yeast, can be used as a fast and reliable evaluation tool to screen new natural lipid-lowering agents. Herein, we showed that triglyceride (TG) accumulation was inhibited by 42.6% in 0.1% red radish coral sprout extract (RRSE)-treated R. toruloides. We also evaluated the anti-obesity effect of the RRSE in a mouse model. The body weight gain of mice fed a high-fat diet (HFD) with 0.1% RRSE (HFD-RRSE) was significantly decreased by 60% compared with that mice fed the HFD alone after the 8-week experimental period. Body fat of the HFD-RRSE-fed group was dramatically reduced by 38.3% compared with that of the HFD-fed group.

The effect of respiration on the phototactic behavior of the purple nonsulfur bacterium Rhodospirillum centenum.

The effect of respiration on the positive phototactic movement of swarming agar colonies of the facultative phototroph Rhodospirillum centenum was studied. When the electron flow was blocked at the bc1 complex level by myxothiazol, the oriented movement of the colonies was totally blocked. Conversely, inhibition of respiration via the cytochrome c oxidase stimulated the phototactic response. No phototaxis was observed in a photosynthesis deficient mutant (YB707) lacking bacteriochlorophylls. Analyses of the respiratory activities as monitored by a oxygen microelectrode in single agar colonies during light/dark transitions showed a close functional correlation between the photosynthetic and respiratory apparatuses. The respiratory chain of Rsp. centenum was formed by two oxidative pathways: one branch leading to a cytochrome c oxidase inhibited by low cyanide concentrations and a second pathway formed by an oxidase less-sensitive to cyanide that also catalyzes the light-driven respiration. These results were interpreted to indicate that (1) there is a cyclic electron transport, and (2) photoinduced cyclic electron flow is required for the phototactic response of Rsp. centenum. Furthermore, under oxic conditions in the light, reducing equivalents may switch from photosynthetic to respiratory components so as to reduce both the membrane potential and the rate of locomotion.

Manganese, an essential trace element for N2 fixation by Rhodospirillum rubrum and Rhodopseudomonas capsulata: role in nitrogenase regulation.

Nitrogenase (N(2)ase) from the photosynthetic bacterium Rhodospirillum rubrum can exist in two forms, an unregulated form (N(2)ase A) and a regulatory form (N(2)ase R), the latter being identified in vitro by its need for activation by a Mn(2+)-dependent N(2)ase activating system. The physiological significance of this Mn(2+)-dependent N(2)ase activating system was suggested here by observations that growth of R. rubrum and Rhodopseudomonas capsulata on N(2) gas (a condition that produces active N(2)ase R) required Mn(2+), but growth on ammonia or glutamate did not. Manganese could not be shown to be required for the biosynthesis of either nitrogenase or glutamine synthetase or for glutamine synthetase turnover, but it was required for the in vitro activation of N(2)ases from N(2) and glutamate-grown R. rubrum and R. capsulata cells. Chromatium N(2)ase, in contrast, was always fully active and did not require Mn(2+) activation, suggesting that only the purple nonsulfur bacteria are capable of controlling their N(2)ase activity by this new type of regulatory system. Although R. rubrum could not substitute Fe(2+) for Mn(2+) in the in vivo N(2) fixation process, Fe(2+) and, to a lesser extent, Co(2+) could substitute for Mn(2+) in the in vitro activation of N(2)ase. Electron paramagnetic resonance spectroscopy of buffer-washed R. rubrum chromatophores showed lines characteristic of Mn(2+). Removal of the Mn(2+)-dependent N(2)ase activating factor by a salt wash of the chromatophores removed 90% of the Mn(2+), which suggested a specific coupling of this metal to the activating factor. The data presented here all indicate that Mn(2+) plays an important physiological role in regulating the N(2) fixation process by these photosynthetic bacteria.

Regulatory properties of the citrate synthase from Rhodospirillum rubrum.

Citrate synthase, purified 600-fold from Rhodospirillum rubrum, is activated by KCl and inhibited by ATP and NADH; the effect of the latter inhibitor is completely counteracted by AMP and partially counteracted by KCl.

Alternative pathways of spirilloxanthin biosynthesis in Rhodospirillum rubrum.

Detailed studies of the properties of carotenoids isolated from diphenylamine-inhibited cultures of Rhodospirillum rubrum have revealed a number of novel structures that indicate new features of carotenoid biosynthesis in the photosynthetic bacteria. Both neurosporene and 7,8,11,12-tetrahydrolycopene undergo hydration, methylation and dehydrogenation to yield spheroidene and 11',12'-dihydrospheroidene respectively; all the intermediates in these pathways have been identified. These pathways represent alternative routes of anhydrorhodovibrin and spirilloxanthin biosynthesis.

A novel sequence for phytoene dehydrogenation in Rhodospirillum rubrum.

Differences between the absorption spectra of zeta-carotene (7,8,7',8'-tetrahydrolycopene) and the corresponding conjugated heptaene from diphenylamine-inhibited cultures of Rhodospirillum rubrum have been rationalized by the identification of the latter compound as the unsymmetrical isomer, 7,8,11,12-tetrahydrolycopene. The structures of the other conjugated polyene hydrocarbons, phytoene, phytofluene and neurosporene, have been confirmed and a novel pathway for the dehydrogenation of phytoene to lycopene in these bacteria is described.