Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary A declining Picea abies (L.) Karst. stand produced as much foliage and branches as a healthy stand but less stemwood at a similar leaf area index and climate. Nutrient analyses revealed that most biomass components at the declining site had lower concentrations of calcium and magnesium, but similar nitrogen and potassium (except for lower potassium in younger needles) and higher phosphorus, manganese and aluminum than the respective components at the healthy site. Comparison of these data with the results from studies on the nutrition and growth of P. abies seedlings (Ingestad 1959) led to the conclusion that the healthy stand is in a balanced nutritional state, while trees at the declining stand have only 56% of the foliar magnesium concentration required to permit growth at a rate which could be achieved at their nitrogen status. It appears that acidic deposition, which involves an input of nitrogen and a leaching of cations from the soil, causes an imbalance in the availability of nitrogen and magnesium. Growth is eventually reduced as magnesium becomes limiting.     

Reduction of nitrosubstituted aromatic compounds by the halophilic anaerobic eubacteria Haloanaerobium praevalens and Sporohalobacter marismortui.

The moderately halophilic, obligately anaerobic eubacteria Haloanaerobium praevalens DSM 2228 and Sporohalobacter marismortui ATCC 35420 are able to reduce a variety of nitrosubstituted aromatic compounds at a high rate to the corresponding amines. Compounds degraded included nitrobenzene, o-nitrophenol, m-nitrophenol, p-nitrophenol, nitroanilines, 2,4-dinitrophenol, and 2,4-dinitroaniline. Most of these compounds, when added at concentrations of 50 to 100 mg/liter, were completely transformed within 24 h, but at the highest concentrations growth rates were somewhat lowered. Growth of H. praevalens in the presence of 14C-labeled p-nitrophenol showed that the compound was not incorporated by the cells or degraded to acid-volatile compounds.     

Isolation and structure determination of a novel compatible solute from the moderately halophilic purple sulfur bacterium Ectothiorhodospira marismortui

The halophilic phototrophic bacterium Ectothiorhodospira marismortui produces three organic osmolytes to counterbalance the osmotic pressure of the surrounding medium: glycine betaine, sucrose, and a novel compound. This new compound, which accounts for approximately 30% of the cells' compatible solutes, was isolated and identified by mass spectrometry and nuclear magnetic resonance. It was characterized as N alpha-carbamoyl-L-glutamine 1-amide, an unusual amino acid derivative with no previous reference in the chemical literature. The relatively high cytoplasmic concentration of this compound (approximately 0.5 M) observed at all growth conditions suggests that it may serve a vital function as an osmoticum and/or protectant for Ectothiorhodospira marismortui in a saline environment.     

Providing or hiding information: On the evolution of amplifiers and attenuators of perceived quality differences

In many coevolutionary systems members of one party select members of a second party based on quality differences existing among members of the latter (e.g., predators and prey, pollinators and flowers, etc.). We examined the fate of characters that increase (amplifiers) or decrease (attenuators) the perceived amplitude of differences in the quality upon which choice of the selecting party is based. We found that the evolution of such characters depends on (i) the relationship between the cost of the character and the relative benefit it gives to the high quality individuals (if an amplifier) or low quality individuals (if an attenuator), and (ii) the frequency, among members of the selected party, of the quality sought by the selecting party.     

Fate of compatible solutes during dilution stress in Ectothiorhodospira marismortui

Abstract The proliferation of murine spleen cells stimulated by a T-cell mitogen such as phytohemagglutinin (PHA) or concanavalin A (ConA) was significantly suppressed when the mice were immunized with either the viable cells or the sonicate of Salmonella typhimurium but not of Escherichia coli . The suppression of T-cell proliferation caused by the sonicate of S. typhimurium was completely restored by addition of phorbol 12-myristate-13-acetate (PMA), an activator of protein kinase C (PKC). Western blots using anti-phosphotyrosine antibodies showed that the mitogen-induced tyrosine phosphorylation of 120-, 106-,94-,76-,68- and 57-kDa proteins in murine splenic T-cells was inhibited in the mice immunized with the viable cells but not the sonicate of S. typhimurium . These results suggest that the inhibition caused by the sonicate involves suppression of PKC activity, whilst that produced by viable cells involves down-regulation of tyrosine phosphorylation, and both inhibitions correlate with the induction of cell-mediated immunity in mice, as evidenced by the induction of delayed-type hypersensitivity reactions.     

Dynamic Diversification from a Putative Common Ancestor of Scorpion Toxins Affecting Sodium, Potassium, and Chloride Channels

Scorpions have survived successfully over millions of years without detectable changes in their morphology. Instead, they have developed an efficient alomonal machinery and a stinging device supporting their needs for prey and defense. They produce a large variety of polypeptidic toxins that bind and modulate ion channel conductance in excitable tissues. The binding site, mode of action, and chemical properties of many toxins have been studied extensively, but little is known about their genomic organization and diversity. Genes representing each of the major classes of Buthidae scorpion toxins, namely, ``long' toxins, affecting sodium channels (alpha, depressant, and excitatory), and ``short' toxins, affecting potassium and chloride channels, were isolated from a single scorpion segment and analyzed. Each toxin type was found to be encoded by a gene family. Regardless of toxin length, 3-D structure, and site of action, all genes contain A+T-rich introns that split, at a conserved location, an amino acid codon of the signal sequence. The introns vary in length and sequence but display identical boundaries, agree with the GT/AG splice junctions, and contain T-runs downstream of a putative branch point, 5′-TAAT-3′. Despite little sequence similarity among all toxin classes, the conserved gene organization, intron features, and common cysteine-stabilized α-helical (CSH) core connecting an α-helix to a three-stranded β-sheet suggest, that they all evolved from an ancestral common progenitor. Furthermore, the vast diversity found among genomic copies, cDNAs, and their protein products for each toxin suggests an extensive evolutionary process of the scorpion ``pharmaceutical factory,' whose success is due, most likely, to the inherent permissiveness of the toxin exterior to structural alterations. Received: 16 March 1998 / Accepted: 30 July 1998