Biosynthesis of unnatural glycolipids possessing diyne moiety in the acyl chain in the green sulfur photosynthetic bacterium Chlorobaculum tepidum grown by supplementation of 10,12-heptadecadiynic acid

AbstractUnnatural glycolipids possessing the diyne moiety in their acyl groups were successfully biosynthesized in the green sulfur photosynthetic bacterium Chlorobaculum (Cba.) tepidum by cultivation with supplementation of 10,12-heptadecadiynic acid. Monogalactosyldiacylglycerol (MGDG) and rhamnosylgalactosyldiacylglycerol (RGDG) esterified with one 10,12-heptadecadiynic acid were primarily formed in the cells, and small amounts of glycolipids esterified with the two unnatural fatty acids can also be detected. The relative ratio of these unnatural glycolipids occupied in the total glycolipids was estimated to be 49% based on HPLC analysis using a evaporative light scattering detector. These results indicate that the acyl groups in glycolipids, which play important roles in the formation of extramembranous antenna complexes called chlorosomes, can be modified in vivo by cultivation of green sulfur photosynthetic bacteria with exogenous synthetic fatty acids. Visible absorption and circular dichroism spectra of Cba. tepidum containing the unnatural glycolipids demonstrated the formation of chlorosomes, indicating that the unnatural glycolipids in this study did not interfere with the biogenesis of chlorosomes

Effect of Nutrient Inputs on Water Quality Change and Phytoplankton Growth in Atsumi Bay

Eutrophication in an estuary occurs as an effect of the enrichment of nutrient inputs from rivers. This condition has become one of the most common environmental issues experienced around the globe and especially in Japan. Atsumi Bay is a eutrophic coastal area in Japan. The objective of this research was to analyze the influences of nutrient inputs from the Umeda River into Atsumi Bay on pre- and post-rainfall water quality conditions. This study was conducted from July to October 2010. The results showed a decrease of surface salinity after rainfall indicating that huge freshwater inputs had overlaid the surface layer of Atsumi Bay rather than the bottom layer. Moreover, post-rainfall conditions showed an increase of chlorophyll a as an effect of phytoplankton growth, followed by an increase of particulate nutrients. On the other hand, dissolved nutrients decreased due to uptake by phytoplankton and dilution by freshwater

Whole-Body Cortisol Concentrations and Ontogeny of Aggressive Behavior in Yellowtail (Seriola quinqueradiataTemminck & Schlegel; Carangidae)

Ontogenetic changes in whole-body immunoreactive cortisol concentrations (IRC) and aggressive behavior were examined in yellowtailSeriola quinqueradiata(Temminck & Schlegel; Carangidae). Baseline IRC significantly increased during the transition from larval to juvenile stage and was correlated with the onset of aggressive behavior. Handled fish (13.1 ± 2.6 ng/g tissue) showed an IRC level about three times higher than unhandled fish (4.7 ± 1.4 ng/g tissue), indicating that whole-body immunoreactive cortisol level may be an indicator of stress in juvenile yellowtails. Behaviorally subordinate fish (8.6 ± 1.6 ng/g tissue,n = 4) showed IRC levels significantly higher than dominant fish (0.6 ± 0.3 ng/g tissue, n = 4). Whole-body immunoreactive cortisol levels may thus reflect stress and social status in juvenile yellowtails, and the inverse relationship between social rank and IRC may result from agonistic interactions

Systematic Analysis of the Demetalation Kinetics of Zinc Chlorophyll Derivatives Possessing Different Substituents at the 3‑Position: Effects of the Electron-Withdrawing and Electron-Donating Strength of Peripheral Substituents

Removal of the central metal from chlorophyll (Chl) molecules is biologically important in terms of production of the primary electron acceptors in photosystem-II photosynthetic reaction centers and the early stage in Chl degradation. The physicochemical properties on demetalation of chlorophyllous pigments are useful in the understanding of such reaction mechanisms in photosynthetic organisms. Here we analyzed the demetalation kinetics of a series of Zn-Chl derivatives with a systematic variation in the electron-withdrawing and -donating substituents at the 3-position of the chlorin macrocycle under acidic conditions to elucidate thoroughly the substitution effects on the demetalation properties of chlorophyllous pigments. Dehydrogenation of the aliphatic group (CH₂CH₃ → CHCH₂ → CCH) at the 3-position slowed the removal of the central zinc from the chlorin macrocycle. The gradual decrease in the demetalation rate constants of the three zinc chlorins originates from differences in the electron-withdrawing strength of the ethyl, vinyl, and ethynyl groups directly linked to the chlorin π macrocycle. Reduction of the 3¹-carbonyl groups significantly increased the demetalation rate constants, and the relative ratios of the demetalation rate constants of the zinc chlorins possessing a carbonyl group to those possessing the corresponding hydroxy group were analogous in the cases of 3-formyl- and 3-acetyl-zinc chlorins. The demetalation rate constants of the seven Zn-Chl derivatives possessing various electron-withdrawing and -donating groups exhibited good correlation with the Hammett σ parameters of the 3-position substituents