Isolation and characterization of an Achromobacter xylosoxidans strain B3 and other bacteria capable to degrade the synthetic chelating agent iminodisuccinate.

Three bacterial strains were isolated, which used the synthetic chelating agent iminodisuccinate (IDS) as sole carbon source for growth in mineral salts media (MSM). Taxonomic analysis and 16S rDNA sequence analysis identified one of these isolates (B3), which was isolated from sewage sludge, as a strain of Achromobacter xylosoxidans subsp. xylosoxidans. It exhibited a doubling time of approximately 3 h in liquid MSM supplemented with IDS and grew even in the presence of 1.0% (w/v) IDS. Since photometric and high performance liquid chromatography analysis showed that IDS, which came onto the market only recently as an alternative for ethylenediaminetetraacetate, was completely degraded by axenic cultures of bacteria; it will probably be readily degraded in the environment.

Comparison of acetate- and pyruvate-dependent fatty-acid synthesis by spinach chloroplasts.

In recent studies using intact chloroplasts of spinach (Spinacia oleracea L.) to investigate the accumulation of acetyl-CoA produced by the activity of either acetyl-CoA synthetase (EC 6.2.1.1) or the pyruvate-dehydrogenase complex, this product was not detectable. These results in combination with new information on the physiological levels of acetate and pyruvate in spinach chloroplasts (H.-J. Treede et al. 1986, Z. Naturforsch. 41 C, 733-740) prompted a reinvestigation of the incorporation of [1-(14)C] acetate and [2-(14)C] pyruvate into fatty acids at physiological concentrations.The K m for the incorporation into fatty acids was about 0.1 mM for both metabolites and thus agreed with the values obtained by H.-J. Treede et al. (1986) for acetyl-CoA synthetase and the pyruvate dehydrogenase complex. However, acetate was incorporated with a threefold higher V max. Saturation for pyruvate incorporation into the fattyacid fraction was achieved only at physiological pyruvate concentrations (<1.0 mM). The diffusion kinetics observed at higher concentrations may be the result of contamination with derivates of the labeled substrate. Competition as well as double-labeling experiments with [(3)H]acetate and [2-(14)C]pyruvate support the notion that, at least in spinach, chloroplastic acetate is the preferred substrate for fatty-acid synthesis when both substrates are supplied concurrently (P.G. Roughan et al., 1979 b, Biochem. J. 184, 565-569).Experiments with spinach leaf discs confirmed the predominance of fatty-acid incorporation from acetate. Radioactivity from [1-(14)C]acetate appeared to accumulate in glycerolipids while that from [2-(14)C]pyruvate was apparently shifted in favor of the products of prenyl metabolism.

Tocopherol synthesis from homogentisate in Capsicum anuum L. (yellow pepper) chromoplast membranes: evidence for tocopherol cyclase.

The present study shows for the first time appreciable tocopherol cyclase activities in plastidial membrane preparations of Capsicum annuum L. (yellow pepper) fruits. When chromoplast membranes from yellow peppers were incubated with [3H]homogentisate and phytyl pyrophosphate under strictly reducing conditions, all biosynthesis precursors were labelled. The main labelling was found in gamma-tocopherol. These observations contradict the hypothesis that assigns a rate-limiting function to tocopherol cyclase in plastidial alpha-tocopherol biosynthesis. The stoichiometry of alpha-tocopherol, 2,3-dimethylphytylquinol and gamma-tocopherol formation and the inhibition of alpha-tocopherol synthesis by increasing gamma-tocopherol concentrations suggests the regulation of this pathway by its precursors.

[Comparative studies on the lipid composition of etioplasts and chloroplasts from Pisum and of chloroplasts from an Aurea mutant of Nicotiana]. / Vergleichende Untersuchungen über die Lipidzusammensetzung von Etioplasten und Chloroplasten aus Pisum sowie von Chloroplasten aus einer Mutante von Nicotiana.

Etioplasts and chloroplasts isolated from Pisum sativum differ in lipid composition. The relative amounts of galactolipids, especially of MGD, are higher in the chloroplast. In contrast, the sulfo- and the phospholipids are already present in the etioplasts in higher concentrations. During the formation of the thylakoids with stacked membranes only the galactolipids are synthesized simultaneously with the pigments. It is suggested that the polar lipids are embedded into the membranes after the basic structure has already been formed.A different type of membrane formation has been described for the chloroplasts of an aurea mutant of tobacco.The grana formation was observed when the plants were grown under lower light intensities. The possibility of a parallel synthesis of polar lipids and pigments is discussed on the basis of the lipid analysis. However, the amount of MGD is lower in the chloroplasts with a higher degree of stacking. The low temperature absorbance spectrum is identical in chloroplasts from yellow and green leaves. Since the mutant is lacking in chlorophyll b, the conclusion can be drawn that this pigment and MGD are not involved in the contact of the grana stacks. From the analysis of lipids released from the membranes under hypotonic conditions, it is concluded that MGD is localized at the surface.

On the light dependence of Fatty Acid synthesis in spinach chloroplasts.

The capacity of intact chloroplasts to synthesize long chain fatty acids from acetate depends on the stroma pH in Spinacia oleracea, U. S. hybrid 424. The pH optimum is close to 8.5. Lowering of the stroma pH leads to a reduction of acetate incorporation but does not suffice to eliminate fatty acid synthesis completely. Chain elongation from palmitic to oleic acid shows the same pH dependence. Fatty acid synthesis is activated in the dark upon the simultaneous addition of dihydroxyacetone phosphate and orthophosphate supplying ATP and oxaloacetate for reoxidation of NADPH in the stroma. Under these conditions both dark fatty acid synthesis and synthesis of oleate from palmitate show the same pH dependence as in the light. Dark fatty acid synthesis is further stimulated by increasing the stromal Mg(2+) concentration with the ionophore A 23187. In contrast to CO(2) fixation, dark fatty acid synthesis is considerably reduced by dithiothreitol (DTT). This observation may be due to an acetyl-CoA deficiency, caused by a nonenzymic acylation of DTT, and a competition for ATP between DTT-activated CO(2) fixation and fatty acid synthesis. Because d,l-glyceraldehyde as inhibitor of CO(2) fixation compensates the DTT effect on dark fatty acid synthesis, reducing equivalents may be involved in the light dependence of acetate activation.

Changes in pigment content, lipid pattern and ultrastructure of synchronous Chlorella after heat and cold shocks.

Completely synchronous Chlorella cultures were treated with heat (45°C) or cold shocks (4° C) of different lengths at the sixth hour of the 14:10 h lightdark-cycle. After the treatment the cells were grown under normal conditions. Analysis at the end of the cycle showed a direct connection between pigment bleaching, reduction of lipid content, loss of thylakoid stacking and a shift of the fluorescence emission maximuminto a region of shorter wavelength. The thylakoid stacking was completely loosened after a heat shock while two thylakoids remained in contact after cold treatment. This probably explains the different regeneration capacities in temperature shock treated cells. None of the described effects could be observed directly after the shocks. From the parallel decay of chlorophyll a, monogalactosyl diglyceride and carotenoids an intimate correlation with the photosystem II complex is suggested.

Chemical behavior of dicyanocob(III)yrinic acid heptamethyl ester and cob(I)yrinic acid heptamethyl ester in some preparative experiments.

Preparations of C10 acetate, trifluoroacetate, and chloro derivatives of dicyanocobyrinic acid heptamethyl ester ('cobester') are described. The nature and properties of intermediates in the synthesis of the 10-chloro derivative are discussed, and the electronic absorption spectra of the products are presented.

Synthesis of medium-chain fatty acids and their incorporation into triacylglycerols by cell-free fractions from Cuphea embryos.

During their rapid maturation period, seeds of Cuphea wrightii A. Gray mainly accumulate medium-chain fatty acids (C8 to C14) in their storage lipids. The rate of lipid deposition (40-50 mg·d(-1)·(g fresh weight)(-1)) is fourfold higher than in seeds of Cuphea racemosa (L. f.) Spreng, which accumulate long-chain fatty acids (C16 to C18). Measurements of the key enzymes of fatty-acid synthesis in cell-free extracts of seeds of different maturities from Cuphea wrightii show that malonyl-CoA synthesis may be a triggering factor for the observed high capacity for fatty-acid synthesis. Experiments on the incorporation of [1-(14)C]acetate into fatty acids by purified plastid preparations from embryos of Cuphea wrightii have demonstrated that the biosynthesis of medium-chain fatty acids (C8 to C14) is localized in the plastid. Thus, in the presence of cofactors for lipid synthesis (ATP, NADPH, NADH, acyl carrier protein, and sn-glycerol-3-phosphate), purified plastid fractions predominantly synthesized free fatty acids, 30% of which were of medium chain length. Transesterification of the freshly synthesized fatty acids to coenzyme A and recombination with the microsomal fraction of the embryo homogenate induced triacylglycerol synthesis. It also stimulated fatty-acid synthesis by a factor 2-3 and increased the relative amount of medium-chain fatty acids bound to triacylglycerols, which corresponded to about 60-80% in this lipid fraction.