Enrichment of purple photosynthetic bacteria from earthworms

Abstract Numerous bacteria present in soil during its passage through the alimentary canal of earthworms resist digestive action and the antimicrobial defenses of the worms. Thus, several kinds of non-sulfur purple photosynthetic bacteria (Rhodospirillaceae) can be enriched from 'purees' of washed earthworms (or from intestinal contents of the worms) using a procedure that exploits the capacity to fix N₂ during anaerobic phototrophic growth with organic acid carbon sources. It appears that earthworm enrichments can be designed to provide highly selective methods for isolation of Rhodomicrobium vannielli and Rhodopseudomonas palustris , and perhaps of other purple bacteria. The extensive burrowing activities of earthworms undoubtedly contributes to the widespread dissemination of Rhodospirillaceae in soils.     

Distribution of C3 and C4 grasses at different altitudes in a temperate arid region of Argentina

Summary The distribution of native C₃ and C₄ grasses in a temperate arid region of Mendoza, Argentina, was studied in six areas at different altitudes. C₄ species predominate at low elevations in both relative species abundance and plant cover. At high elevations C₃ species are dominant in cover and composition. At medium altitudes (1100–1600 m) grass species composition is balanced but plant cover of C₃ species is greater. Of 31 genera in the whole area, 19 were C₄. Only the genera Stipa (C₃) and Aristida (C₄) were present in all the six areas surveyed. The pattern of grass distribution shows high correlation with evapotranspiration and temperature parameters, but low correlation with rainfall. The relation between grass distribution and different climatic parameters is discussed.     

Introducing extra NADPH consumption ability significantly increases the photosynthetic efficiency and biomass production of cyanobacteria

Increasing photosynthetic efficiency is crucial to increasing biomass production to meet the growing demands for food and energy. Previous theoretical arithmetic analysis suggests that the light reactions and dark reactions are imperfectly coupled due to shortage of ATP supply, or accumulation of NADPH. Here we hypothesized that solely increasing NADPH consumption might improve the coupling of light reactions and dark reactions, thereby increasing the photosynthetic efficiency and biomass production. To test this hypothesis, an NADPH consumption pathway was constructed in cyanobacterium Synechocystis sp. PCC 6803. The resulting extra NADPH-consuming mutant grew much faster and achieved a higher biomass concentration. Analyses of photosynthesis characteristics showed the activities of photosystem II and photosystem I and the light saturation point of the NADPH-consuming mutant all significantly increased. Thus, we demonstrated that introducing extra NADPH consumption ability is a promising strategy to increase photosynthetic efficiency and to enable utilization of high-intensity lights.     

多变鱼腥藻在不同氮源培养条件下光能转换效率的研究

依公式PE=KY,其中K等于生物量的热值(每克干重千卡),Y等于产率即每吸收千卡光能所产生的生物量的干重,测试了在无氮和有结合氮培养下的多变鱼腥藻(Anabaena variabilis)的光能转化效率。结果指出在无氮培养下的最高PE_(N2)为8.1%,在结合氮(NH_4Cl)培养下PE_(NH_4~ )为5.8%。对这种差异性作了简要讨论。     

Effect of Cytokinins on Photosynthetic Pigments and Chlorophyllase Activity in in Vitro Cultures of Axillary Buds of Dianthus caryophyllus L.

The effect of benzyladenine (BA) and two phenylurea cytokinins, N-phenyl-N′-(2-chloro-4-pyridyl)urea (4-PU-30) and thidiazuron (TDZ), on the growth, photosynthetic pigment content, and activity of chlorophyllase (chlorophyll-chlorophylliodhydrolase, EC 3.1.1.14) of in vitro cultures of carnations was studied. All cytokinins caused a rise in the fresh weigth and a drop in the dry weight of leaf mass produced by the explanted buds. Both 4-PU-30 and TDZ increased the chlorophyll content and this correlated with changes in chlorophyllase activity. The effect of 4-PU-30 and TDZ was similar to that caused by BA but at 10-fold or 100-fold lower concentrations. The application of higher concentrations of the phenylurea cytokinins caused an increase in the chlorophyll a/chlorophyll b ratio. However, at equimolar concentrations, the purine and both phenylurea cytokinins had opposite effects, probably indirect and related to some malformations caused by phenylureas. 4-PU-30 increased, but TDZ decreased, photosynthetic membrane stability, which argues for a different molecular organization of the chloroplast membranes. Received February 26, 1996; accepted May 30, 1997     

Gamma radiation effects on seed germination, growth and pigment content, and ESR study of induced free radicals in maize (Zea mays)

The effects of gamma radiation are investigated by studying plant germination, growth and development, and biochemical characteristics of maize. Maize dry seeds are exposed to a gamma source at doses ranging from 0.1 to 1 kGy. Our results show that the germination potential, expressed through the final germination percentage and the germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose. Moreover, plants derived from seeds exposed at higher doses (≤0.5 kGy) did not survive more than 10 days. Biochemical differences based on photosynthetic pigment (chlorophyll a, chlorophyll b, carotenoids) content revealed an inversely proportional relationship to doses of exposure. Furthermore, the concentration of chlorophyll a was higher than chlorophyll b in both irradiated and non-irradiated seedlings. Electron spin resonance spectroscopy used to evaluate the amount of free radicals induced by gamma ray treatment demonstrates that the relative concentration of radiation-induced free radicals depends linearly on the absorbed doses.     

Effects of ultraviolet radiation and water motion on the reef coral, Porites compressa Dana: a transplantation experiment

Scleractinian corals have adapted to live in habitats were the level of ultraviolet radiation (UVR, 280–400 nm) is extremely high. The putative photoprotective molecules called mycosporine-like amino acids (MAAs) contained in the corals' tissues absorb UVR and release it harmlessly as heat. MAA concentration in corals is quite plastic and correlates well with UVR dose, but other ecological factors such as water motion may influence MAA production as well. In this study, the effects of ambient UVR and water motion on MAA concentration and several physiological parameters of the reef coral Porites compressa Dana were investigated in a two by two factorial transplantation experiment. Replicate branches from nine morphologically distinct colonies were transplanted from the windward side of Coconut Island (Kaneohe Bay, HI) to a control area on the windward side (ambient water motion) and to an area on the leeward side (low water motion). The transplanted corals were placed under UV-opaque (UVO) or UV-transparent (UVT) filters fixed to the reef. Initially and at 3 and 6 weeks, coral branches were weighed to determine calcification rate and tissues were extracted in methanol for photosynthetic pigment and MAA analysis via high performance liquid chromatography (HPLC). UVR was a significant factor determining MAA concentration. When UVR was screened from the corals' environment, total MAA concentration decreased by 33% over 6 weeks. However, UVR-exposed corals moved to low water motion also decreased MAA levels, while UVR-exposed corals moved to the control area retained initial levels. Photosynthetic pigments and calcification rate were also significantly reduced in corals moved to low water motion. There was no UVR effect on photosynthetic pigments or calcification rate. This study provides evidence that water motion is important for the maintenance of MAAs. However, there were interesting colony-specific patterns in MAA composition and response to the UVR treatment; some colonies had high total concentrations of MAAs in all treatments, while others displayed a pronounced UVR effect. Also, each genotype seemed to have its own signature MAA composition. These findings indicate a genetic (host, zooxanthellae or both) component to UVR resistance in this population of P. compressa.