Pulsed-field gel electrophoresis for genotypic comparison of Rhizobium bacteria that nodulate leguminous trees

Abstract Pulsed-field gel electrophoresis (PFGE) was applied to characterize Rhizobium bacteria isolated from the root nodules of Acacia senegal and Prosopis chilensis trees growing in Sudan and Keya. For the electrophoresis, the total DNA of 42 isolates, embedded in agarose, was digested by a rare-cutting restriction endonuclease, Xba I. The PFGE run resulted in good resolution of the DNA fragments and gave the strains distinctive fingerprint patterns. The patterns were analysed visually and using automated clustering analysis, which divided the strains into groups resembling the results generated by numerical taxonomy. However, several strains had unique banding patterns, which indicates that these strains are genetically very diverse.     

Attempt to detect recombination between B-F and B-L genes within the chicken B complex by serological typing,in vitro MLR,and RFLP analyses

In search for recombinants within the chicken major histocompatibility B complex, 1155 animals from crosses between the congenic lines CB (B¹²) and CC (B⁴) were tested with alloantibodies and monoclonal antibodies for the B-F (class I), B-L (class II), and B-G (class IV) antigens and by mixed lymphocyte reaction. The absence of detectable recombination was confirmed by restriction fragment length polymorphism analysis with B-L and B-F probes. Together with previous reports, this indicates that the distance between the B-F and B-L loci is below 0.01 centimorgan.     

An acetyl esterase of Trichoderma reesei and its role in the hydrolysis of acetyl xylans

Summary An acetyl esterase was purified from Trichoderma reesei by cation and anion exchange chromatography. The enzyme had a molecular weight of 45 000 as determined by SDS-electrophoresis, or 67 000 as determined by gel filtration. In chromatofocusing the enzyme was shown to consist of two isoenzymes with isoelectric points of 6.8 and 6.0. The enzyme showed activity towards naphthyl acetate, triacetin and glucose-and xylose acetates. However, it liberated acetic acid from acetylated xylo-oligomers only to a small extent. The liberation of acetic acid from the oligomeric substrate was enhanced by addition of endoxylanase and -xylosidase.     

Simultaneous degradation of the herbicides 2,4-dichlorophenoxyacetic acid and 2-(2-methyl-4-chlorophenoxy)propionic acid by mixed bacterial cultures

The simultaneous degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop) was achieved by two mixed cultures in the absence of any additional carbon or energy substrates. Mecoprop was not completely degraded by either of the two cultures, nor did addition of 2,4-D affect the degradation of mecoprop. The cultures completely degraded 2,4-D, and the degradation was uninfluenced by the addition of mecoprop. Nearly complete dechlorination of the mixture of two herbicides was achieved by both cultures, on the basis of the total amount of the two herbicides degraded. During the course of the reaction, however, the expected values of chloride were not met. Cell growth continued after the degradation of the parent substrates ceased. Although the mecoprop degradation did not continue to completion, spectral and growth data indicated that the metabolites which had accumulated during the reaction were degraded upon further incubation.     

Studies on the growth ofThiobacillus ferrooxidans

Summary Uranyl sulphate (0.2–0.9 mM) inhibited ferrous iron oxidation by growing cultures ofThiobacillus ferrooxidans. The addition of 5–100 mM uranium to the cultures caused immediate cessation of carbon dioxide fixation, rapid loss of viability and gradual depression of ferrous iron oxidation. Virtually no uranium was found in washed cells grown in the presence of subtoxic to toxic amounts of uranyl sulphate. Uranium-poisoned organisms appeared plasmolyzed in electron micrographs. Cultures tolerant to 5 mM UO₂ ²⁺ were develoepd by successive subculturing in increased uranium concentrations. The tolerance was maintained during subculturing in uranium-free medium. Frequency of mutants resistant to 1.0 and 1.5 mM UO₂ ²⁺ was 1 per 1.3×10⁶ and 1 per 9.0×10⁸, respectively. The frequency was increased in the presence of 15–150 mM nickel, zinc and manganese. In liquid cultures, bivalent cations and EDTA alleviated the toxicity of 2 mM uranyl sulphate.     

Bacterial Oxidation of Sulfide Minerals in Column Leaching Experiments at Suboptimal Temperatures

The purpose of the work was to quantitatively characterize temperature effects on the bacterial leaching of sulfide ore material containing several sulfide minerals. The leaching was tested at eight different temperatures in the range of 4 to 37°C. The experimental technique was based on column leaching of a coarsely ground (particle diameter, 0.59 to 5 mm) ore sample. The experimental data were used for kinetic analysis of chalcopyrite, sphalerite, and pyrrhotite oxidation. Chalcopyrite yielded the highest (73 kJ/mol) and pyrrhotite yielded the lowest (25 kJ/mol) activation energies. Especially with pyrrhotite, diffusion contributed to rate limitation. Arrhenius plots were also linear for the reciprocals of lag periods and for increases of redox potentials (dmV/dt). Mass balance analysis based on total S in leach residue was in agreement with the highest rate of leaching at 37 and 28°C. The presence of elemental S in leach residues was attributed to pyrrhotite oxidation.     

Adenylyl Cyclases: mRNA and Characteristics of Enzyme Activity in Three Areas of Brain

Abstract: Arachidonic acid and oleoylacetylglycerol enhance depolarization-evoked glutamate release from hippocampal mossy fiber nerve endings. It was proposed this is a Ca²⁺-dependent effect and that protein kinase C is involved. Here we report that arachidonic acid and oleoylacetylglycerol synergistically potentiate the glutamate release induced by the Ca²⁺ ionophore ionomycin. The Ca²⁺ dependence of this effect was established, as removal of Ca²⁺ eliminated evoked release and the lipid-dependent potentiation. Also, Ca²⁺ channel blockers attenuated ionomycin- and KCI-evoked exocytosis, as well as the facilitating effects of the lipid mediators. Although facilitation required Ca²⁺, it may not involve an enhancement of evoked Ca²⁺ accumulation, because ionomycin-dependent glutamate release was potentiated under conditions that did not increase ionomycin-induced Ca²⁺ accumulation. Also, the facilitation may not depend on inhibition of K⁺ efflux, because enhanced release was observed in the presence of increasing concentrations of 4-aminopyridine and diazoxide did not reduce the lipid-dependent potentiation of exocytosis. In contrast, disruption of cytoskeleton organization with cytochalasin D occluded the lipid-dependent facilitations of both KCI- and ionomycin-evoked glutamate release. In addition, arachidonic acid plus glutamatergic or cholinergic agonists enhanced glutamate release, whereas a role for protein kinase C in the potentiation of exocytosis was substantiated using kinase inhibitors. It appears that the lipid-dependent facilitation of glutamate release from mossy fiber nerve endings requires Ca²⁺ and involves multiple presynaptic effects, some of which depend on protein kinase C.     

FGF-2 Inhibits Apoptosis in Human Teratocarcinoma Cells during Differentiation on Collagen Substratum

Tera-2 is a human teratocarcinoma cell line, which is induced to differentiate into neuronal direction by retinoic acid. Once differentiated, the cells form an almost nondividing population that can be maintained for weeks under conventional culture conditions. If differentiation by retinoic acid is induced while the cells are growing on type I collagen or if the already-differentiated cells are transferred onto collagen, they survive only a few days unless the cultures are repeatedly supplied with FGF-2. Lack of this growth factor induces programmed cell death (apoptosis) detectable after 24–48 h, as marked by DNA cleavage and nuclear fragmentation. The undifferentiated stem cells survive and proliferate readily on collagen without addition of FGF-2. Tera-2 cells express two members of the FGF family, FGF-2 and FGF-4. The expression of both FGFs is turned off during differentiation on collagen substratum, whereas when cultivated on plain tissue culture dish, the expression of only FGF-4 becomes undetectable. The results indicate that signaling through cell surface FGF receptors is vital for the cells, and differentiation on collagen substratum results in complete extinction of the autocrine stimulatory loop.In vivo,such induction of growth factor dependency upon differentiation would result in apoptotic death of those cells which fail to find adequate conditions for continuing FGF stimulation.