Change in the H2 photoproduction capability in a synchronously grown aerobic nitrogen-fixing cyanobacterium,Synechococcus sp. Miami BG 043511

Synchronously growing cells of nitrogen-fixing Synechococcus sp. Miami BG 043511 were harvested periodically and the capability for hydrogen photoproduction in closed vessels was measured under hydrogen production conditions. The capability for hydrogen photoproduction in cells was correlated with that of cellular carbohydrate content. Cells with a high carbohydrate content exhibited a high capacity for hydrogen production and those with low carbohydrate content exhibited low capacity for hydrogen production. Nitrogenase activity at the onset of incubation did not coincide with a capability for the cells to produce hydrogen during the subsequent incubation period. Interestingly, when cells with a high capacity for hydrogen photoaccumulation were incubated, alternate periods of hydrogen and oxygen accumulation were observed at 12 hour intervals. About 0.5 ml of hydrogen per ml of cell suspension was accumulated in flasks during the initial 12-h incubation period. These observations indicate that the use of synchronous culture can be one of the ways of provide materials suitable not only for basic studies but also for applied aspects of hydrogen photoproduction.     

Denitrifying population dynamic and evolution of nitrogen gas during a composting process

Abstract Little information exists about nitrogen losses through microbial activity during treatment of solid urban waste (SUW) by processes such as composting. In the present study, in addition to evaluating the pattern of nitrogen losses by denitrification at different stages of the process, a comparison between the method of Pochon and Tardieux, and an improved gas chromatographic method for estimating denitrifying populations was undertaken, Though the MPN (Most Probable Number) enumerations were higher using the colorimetric method than the gas chromatographic one, the patterns of the two graphs showing numbers of denitrifiers during composing were the same. The highest numbers were revealed immediately after loading the reactor (10⁷–10⁸/g d.w.), lower numbers of denitrifiers were found in the second sampling corresponding to the thermophilic phase (10³–10⁴/g d.w.). These numbers increased gradually as the waste material stabilized (10th to 123rd day of composting) to again reach values of 10⁷–10⁸/g d.w.     

Light energy supply in plate-type and light diffusing optical fiber bioreactors

The light distribution profiles of plate-type photobioreactors were investigated. Light reaching individual channels of a plate module is dependent on the orientation of the module to the sun, the position of the channel within a plate and the position of the plate. The highest incident radiation was measured at the south oriented side of the first channel of the front plate. The light intensity decreased from top to ground channels. Different types of light diffusing optical fibers (LDOF) were characterized with respect to their applicability in photobioreactor systems.     

The effect of CuSO4 for establishing in vitro culture,and the role nitrogen and iron sources in in vitro multiplication of Corylus avellana L. cv. Tonda Gentile Romana

Abstract

In the present work, we have used copper sulphate (CuSO₄·5H₂O) enriched medium for effective control of visible and latent contamination. Among the different concentrations used, 1.25–2.5?mg/L resulted the most appropriate. In addition, the role of different nitrogen source and concentrations (NH₄NO₃ and KNO₃), as different iron source (FeEDTA and FeEDDHA) has been investigated in the proliferation and rooting phases of European hazelnut (cv. Tonda Gentile Romana). The normal concentration of nitrogen present in Murashige and Skoog medium is too high for hazelnut micropropagation cv. Tonda Gentile Romana. A reduction of total nitrogen, accompanied by a reduction of ammonium forms, resulted in a better quality of the shoots. Similar results have been obtained when the common iron source FeEDTA has been replaced by the same concentration of FeEDDHA. An increase in rooting occurs when the amount of nitrogen was reduced in the rooting medium, particularly when the NH₄NO₃ was not present.     

Senescence and N release from clover roots following permanent excision of the shoot

Six to seven week old red clover plants (Trifolium pratense L. cv Merviot) were used to investigate the time-course of root senescence following complete and permanent excision from the shoot. Plants were grown in sand culture watered with nutrient solution. After excision of the shoots, roots were left in situ and sampled over a period of up to 42 days. Respiration rate began to decrease immediately after excision, reaching 50% of its initial value after 24 h. The decline involved a reduction in the capacity of the respiratory pathways as measured in the presence of an uncoupler (FCCP) and exogenous glucose. The reduction in respiration could be prevented by supplying 100 mM sucrose to excised roots incubated in nutrient solution at the time of excision, but not 4–5 days after excision. There was a steady reduction in the protein and soluble sugar concentrations from the time of excision and a smaller reduction in starch. Free amino acid concentrations increased immediately after excision, but the temporal dynamics differed between individual amino acids. The total concentration of free amino acids rose to a maximum value 6–13 days after excision, before declining. Under these conditions roots survived for a remarkably long period of time. Depending on the experiment, cell viability, measured as the percentage of cells with positive turgor, was unchanged for at least 20 days, and complete loss of viability was not observed until 34–42 days after excision. There was no appreciable loss of N from the roots until cell viability declined significantly. The potential implications of these results for modelling and management of N cycling in cropping systems is discussed briefly.     

Survival costs of reproduction vary with age in North American red squirrels

The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits.     

Cardiac myoglobin deficit has evolved repeatedly in teleost fishes

Myoglobin (Mb) is the classic vertebrate oxygen-binding protein present in aerobic striated muscles. It functions principally in oxygen delivery and provides muscle with its characteristic red colour. Members of the Antarctic icefish family (Channichthyidae) are widely thought to be extraordinary for lacking cardiac Mb expression, a fact that has been attributed to their low metabolic rate and unusual evolutionary history. Here, we report that cardiac Mb deficit, associated with pale heart colour, has evolved repeatedly during teleost evolution. This trait affects both gill- and air-breathing species from temperate to tropical habitats across a full range of salinities. Cardiac Mb deficit results from total pseudogenization in three-spined stickleback and is associated with a massive reduction in mRNA level in two species that evidently retain functional Mb. The results suggest that near or complete absence of Mb-assisted oxygen delivery to heart muscle is a common facet of teleost biodiversity, even affecting lineages with notable oxygen demands. We suggest that Mb deficit may affect how different teleost species deal with increased tissue oxygen demands arising under climate change.