The effect of salinity on the composition of fatty acid double-bond isomers andsn-1/sn-2 positional distribution in membrane phospholipids of a moderately halophilic eubacterium

We report the first study of the effect of NaCl on the double-bond isomeric composition of fatty acids and theirsn-1/sn-2 positional distribution in the membrane phospholipids of a moderately halophilic eubacterium. The major phospholipids, phosphatidylethanolamine and phosphatidylglycerol, ofVibrio costicola grown in 1M or 3M NaCl both have ansn-1 saturated,sn-2 unsaturated distribution of fatty acids. There is a greater effect of salinity on the fatty acid composition of phosphatidylglycerol compared with phosphatidylethanolamine. The fatty acids in phosphatidylethanolamine of cultures grown in 1M compared with 3M NaCl have the same unsaturation index and average chain length, but different double-bond isomeric compositions. In comparison, the fatty acid composition of phosphatidylglycerol is more unsaturated, with a different double-bond isomeric distribution, and has a shorter average chain length in cultures grown in 3M compared with 1M NaCl. The pattern of fatty acid isomers of 16:1 and 18:1 shows thatV. costicola uses the anaerobic pathway of fatty acid biosynthesis. The presence of the isomers 16:1c11 and 18:1c13 in the phospholipids of cultures grown in 3M but not in 1M NaCl indicates that external salinity affects the specificity of fatty acid synthetase in this moderately halophilic bacterium.     

Cold adaptation of microorganisms

Psychrophilic and psychrotrophic microorganisms are important in global ecology as a large proportion of our planet is cold (below 5 degrees C); they are responsible for the spoilage of chilled food and they also have potential uses in low-temperature biotechnological processes. Psychrophiles and psychrotrophs are both capable of growing at or close to zero, but the optimum and upper temperature limits for growth are lower for psychrophiles compared with psychrotrophs. Psychrophiles are more often isolated from permanently cold habitats, whereas psychrotrophs tend to dominate those environments that undergo thermal fluctuations. The molecular basis of psychrophily is reviewed in terms of biochemical mechanisms. The lower growth temperature limit is fixed by the freezing properties of dilute aqueous solutions inside and outside the cell. In contrast, the ability of psychrophiles and psychrotrophs to grow at low, but not moderate, temperatures depends on adaptive changes in cellular proteins and lipids. Changes in proteins are genotypic, and are related to the properties of enzymes and translation systems, whereas changes in lipids are genotypic or phenotypic and are important in regulating membrane fluidity and permeability. The ability to adapt their solute uptake systems through membrane lipid modulation may distinguish psychrophiles from psychrotrophs. The upper growth temperature limit can result from the inactivation of a single enzyme type or system, including protein synthesis or energy generation.     

Internal waves, primary production and the compensation depth of marine phytoplankton

Internal waves increase the average light intensity experiencedby phytoplankton and augment the compensation depth below whichno net photosynthesis occurs. These effects may be quite largein eutrophic waters with moderate or high light attenuationcoefficients. Data on internal waves and light attenuation canbe used to correct standard estimates of (new) primary productionin the lower euphotic zone based on uptake rates of carbon ornitrogen isotopes.     

Bone marrow derived macrophages have polyamine and ectoenzyme phenotypes distinct from resident macrophages

Several prototype macrophage (MO) populations were compared for differences in ectoenzyme phenotype and polyamine content. Resident peritoneal MO and Corynebacterium parvum (CP)-activated peritoneal MO expressed unique ectoenzyme phenotypes, while bone marrow derived MO (BMDMO), obtained from stem cells after 7 days in culture with colony stimulating factor, and thioglycollate (TG)-elicited peritoneal MO exhibited a similar ectoenzyme phenotype. All of the MO populations, however, differed in polyamine accumulation patterns. These results suggest that ectoenzyme phenotypes do not serve as completely selective markers of MO differentiation. Moreover, BMDMO do not resemble steady state tissue peritoneal MO but appear to resemble inflammatory MO in several respects. Therefore activated BMDMO do not appear to provide an accurate model system for their continued use in studies to characterize the development of resident tissue MO.     

Effect of biologically active plants used as netst material and the derived benefit to starling nestlings

Summary The European starling Sturnus vulgaris preferentially incorporates fresh sprigs of particular plant species for use as nesting material. Chemicals found in these plants may act to reduce pathogen and ectoparasite populations normally found in nest environments. The present experiments were performed to test this Nest Protection Hypothesis. In the fild, we experimentally determined that wild carrot Daucus carota, a plant species preferred as nest material, effectively reduced the number of hematophagous mites found within nests relative to control nests without green vegetation. Chicks from nests containing wild carrot had higher levels of blood hemoglobin than chicks from control nests. However, there were no differences in weight or feather development. In the laboratory, we found that wild carrot and fleabane, Erigeron philadelphicus, (also preferred by starlings as nest material) substantially reduced the emergence of feeding instars of mites, while garlic mustard, Alliaria officinalis, (commonly available but not preferred) had little effect on the emergence of mites. We infer that preferred plant material may act to inhibit feeding or otherwise delay reproduction of mites, thereby reducing risk of anemia to developing nestlings.     

Inhibitor-induced enzyme activation in organic solvents

The enzymatic activity of the protease subtilisin in anhydrous organic solvents can be dramatically increased by pretreating the enzyme before it is placed in the nonaqueous medium. For instance, lyophilization of subtilisin from aqueous solution containing competitive inhibitors (followed by their removal) created an enzyme which was up to 100 times more active than the enzyme lyophilized in the absence of such ligands. This phenomenon of ligand-induced "enzyme memory" also extends to the stability, affinity, and substrate specificity of subtilisin in organic solvents.     

Biochemical differentiation in the tobacco flower probed with monoclonal antibodies

We have isolated a series of monoclonal antibodies that react to antigens in flowers of Nicotiana tabacum L. (tobacco) displaying specificity or preferentiality in their cell and tissue distributions. We immunized mice with extracts from tobacco flowers and then screened the hybridomas by enzyme-linked immunosorbent assay (ELISA) against extracts from leaves, sepals, petals, stamens and pistils; twenty five were chosen from the total screened. The antigens detected by about half of the antibodies were periodate-sensitive, implying that the epitopes were carbohydrate. Competition ELISA assays were used to determine if any antibodies were reacting to the same epitopes. Western blot analysis showed that while some antibodies reacted to specific bands, the bulk either failed to react or reacted to multiple bands, consistent with a glyco-conjugate nature for many of the antigens. Analysis of the spatial pattern of antigen distribution within tobacco flowers by immunolocalization showed that some antibodies recognized epitopes that were limited to very specific cells and tissues. We used the immunolocalization technique to analyze a mutant with stigmoid anthers: an antibody recognizing a pistil transmitting-tract antigen also reacted to cells in stigmoid anthers. Our results with this antibody set imply that biochemical differentiation within the tobacco flower includes cell-and tissue-specific glyco-moeities, and also that similarities, at the biochemical level, exist between a normal floral organ and the abnormal organ in a phenotype with a developmental switch.Abbreviations ELISA enzyme-linked immunosorbent assay - Fg immunoglobulin - kDa kilodalton     

Recovery of plants from leaf protoplasts of hybrid-poplar and aspen clones

Leaf protoplasts were isolated from shoot cultures of two hybrid poplar clones (Populus alba × P. grandidentata Crandon, NC-5339 and P. nigra Betulifolia × P. trichocarpa, NC-5331) and the Upright European Aspen (P. tremula Erecta) and were cultured in contact with screen discs floated in liquid medium. Protoplast culture was influenced by the growth medium of the source shoot cultures, the protoplast purification procedure, the plating density, and the presence or absence of a coconut water and casein hydrolysate supplement added to the culture medium. The protoplast-derived cells divided more quickly and with higher incidence than previously reported for hybrid poplars. Shoots were regenerated from the protoplast-derived calli and were maintained as shoot cultures. Plants were developed from microcuttings rooted ex vitro and were grown-on in the greenhouse and field.Abbreviations BA benzyladenine - NAA 1-naphthaleneacetic acid - TDZ thidiazuron - WPM Woody Plant Medium, Lloyd and McCown (1980) - MS Murashige and Skoog Medium (1962) - NC-XXXX North Central Forest Experiment Station accession number assigned to hybrid poplar clones.