Studies on nitric oxide (NO) formation by the green alga Scenedesmus obliquus and the diazotrophic cyanobacterium Anabaena doliolum.

This study provides preliminary evidence that NO production could be a general attribute of algae. Anabaena doliolum was found to be a better NO producer than Scenedesmus and Synechoccocus. Experiments conducted with inhibitors of photosynthesis (DCMU), ATP synthesis (DCCD), and the uncoupler (2,4-DNP) and its analog arsenate clearly revealed that inhibition of nitrite assimilation through the blockage of nitrite reductase (NiR) is primarily responsible for NO emission. A linear relationship between nitrite concentration in the culture medium and NO in the exhaust gas supports the view that accumulation of nitrite is responsible for NO formation. A failure of Scenedesmus, grown in the medium substituted with W for Mo, to produce either NO/NO-2 in light or a 'light-off' peak, and a resumption of these activities upon the addition of Mo proved beyond doubt that a functional nitrate reductase (NR) is necessary for the production of nitrite and NO by algae grown on nitrate as the nitrogen source. Moreover, the appearance of a NO peak immediately after nitrite supplementation under dark conditions in W-substituted cultures with or without glucose ruled out an enzymatic role of NR in NO emission.

Biotransformation of 1-naphthalenesulfonic acid by the green alga Scenedesmus obliquus.

Under sulfate limitation, axenic batch cultures of the green alga Scenedesmus obliquus metabolized 1-naphthalenesulfonic acid and partially used the sulfonate as a source of sulfur. The main metabolite, 1-hydroxy-2-naphthalenesulfonic acid, which was not metabolized further in the algal culture, was formed by hydroxylation of the substrate in position 1 and by migration of the sulfonic acid group to position 2 of the naphthalene ring (NIH shift). A smaller amount of 1-naphthalenesulfonic acid was desulfonated. The resulting 1-naphthol was mostly transformed into 1-naphthyl beta-d-glucopyranoside.

Influence of phytogenic surfactants (quillaya saponin and soya lecithin) on bio-elimination of phenanthrene and fluoranthene by three bacteria.

The influence of two phytogenic surfactants on the elimination of polycyclic aromatic hydrocarbons (PAH) was studied in shaken-batch cultures of three soil bacteria under axenic conditions. At sufficiently high concentrations, quillaya saponin and soybean lecithin solubilized phenanthrene or fluoranthene efficiently. However, complete solubilization of the PAH by lecithin only doubled the maximal rate of elimination of the two PAH compounds by Pseudomonas 0259, strain MKm (Rhizomonas ?) and Mycobacterium EMI 2. By contrast, quillaya saponin did not improve PAH bioavailability, and in strain MKm it caused significant growth lags above 2.5 g/l. Simultaneously with the elimination of the PAH the bacteria utilized the surfactants as substrates for growth. Intermediate formation of PAH metabolites was noted. The results suggest that some phytogenic surfactants might improve PAH bioavailability in rhizospheres.

Deterministic interpretation of the temperature response of microbial growth.

A deterministic approximation of the thermal deactivation process is undertaken by structuring growth kinetics of cell populations on the activity level. Growth data of the green microalga Scenedesmus obliquus under forced periodic conditions of light intensity have been used for model verification. The model considers a straightforward extension of normal growth kinetics in such a way that different growth activities can be adjusted in the context of a thermal damage and repair mechanism. The nonlinear fitting of the measured response renders parameter values as a function of the light availability per unit biomass.

Amines in Algae. 8. Effects of a Modified Light Regime and of Inhibitors of DNA Synthesis on Polyamine Levels in Synchronous Chlorella emersonii.

Chlorella emersonii (strain 211-8b) was grown synchronously in a 16 : 8 h light-dark cycle. The normal kinetic coincidence between the concentration changes per initial cell of DNA, putrescine, and spermidine disappeared to a greater or lesser degree upon shifting the light-dark cycle from 16 :8 h to 10 : 14 h as well as in the presence of inhibitors of DNA synthesis. For example, timing, and initial rates of synthesis of putrescine and spermidine remained normal, when DNA synthesis was blocked by 5-fluoro deoxy uridine. Also during recovery from the unspecific inhibition by hydroxy urea the DNA/putrescine/spermidine coincidences disappeared. Hence, these coincidences which are observed under standard conditions, may be essentially incidental. By contrast, the RNA/norspermidine coincidence was maintained to a greater or lesser extent under all conditions tested. The concentration of norspermidine was found to be 25 ± 5 mg per gram of RNA.

[Use of microalgae for nutritional purposes]. / Zur Verwendung von Mikroalgen für Ernährungszwecke

Mass cultures of planktonic microalgae can render large quantities of proteinaceous matter. The good nutritional quality of microalgal protein has been proven both for animals and for human. The toxicologic safety of microalgal biomasses is, however, not yet sufficiently established. This requires further toxicologic studies, before cultivated mocralgae can commercially be utilized as ingredients of animal feed, or as food additives. Both types of nutritional application may become economically feasible.

CARBON DIOXIDE-INDUCED DELAY OF CELLULAR DEVELOPMENT IN TWO CHLORELLA SPECIES(1).

Two species of Chlorella, C. fusca and C. vannielii, manifest delay in cell development in synchronous cultures when gassed with air enriched with 1.5% vol. C02 or higher. This effect is greater if the final developmental steps proceed in the light rather than in the dark. Despite this, as much as 5% vol. CO2 does not decrease the production of dry matter in continuous light. It is not unlikely that this action of CO2 is restricted to cases in which nitrate serves as the only N source.