Mitochondria and mitochondrial nucleoids (mt-nucleoids) of the yeast, Saccharomyces cerevisiae were vitally double-stained with two fluorochromes, 3, 3′-dihexyloxacarbocyanine iodide [DiOC6(3)] and 4′, 6-diamidino-2-phenylindole (DAPI), respectively in different types of cells during the life cycle. Budded cells at logarithmic phase had a single, branched, giant mitochondrion, a part of which migrated into the daughter cell prior to nuclear division. Mt-nucleoids appeared as a string-of-beads within a giant mitochondrion. Single cells at stationary phase had numerous fragmented mitochondria with dot-like mt-nucleoids. When stationary-phase cells were transferred to the sporulation medium, fragmented mitochondria fused with each other and a network of mitochondrion changed its configuration as the meiotic division proceeded. Finally, mitochondria formed four rings which enclosed each daughter nucleus in premature spores. Mitochondria were hardly stained with DiOC6(3) in mature spores. Fused mitochondria were clearly observed again in cells at germination and outgrowth. When cells of opposite mating type were mixed in mating medium, zygote formation and first bud emergence occurred in 4h. Just after mating, string-like and fragmented mitochondria transmitted from each parent cell were separately visible on both sides of a dumbbell-shaped zygote. In contrast, extensive fusion of mitochondria occurred in zygotes with a first bud.
Predation of algae by amoebae has been commonly reported in laboratory, but scarcely studied in natural ecosystems. Feeding selectivity and behavior of Thecamoeba sphaeronucleolus was studied from samples taken from a small eutrophic pond. Mougeotia sp. (77%) and Phormidiumautumnale (12%) were the dominant algal species. P. autumnale was the most extensively predated algae by T. sphaeronucleolus, although both major algal species were similar in size. Cyanobacteria cell-wall structure and trichome flexibility, together with the capacity for gliding movement seem important to explain this selective predation. The two specific mechanisms for filaments ingestion by this amoeba are described.
Fe3+-dicitrate binding and iron uptake from citrate have been characterized in three carrier and three case isolates of Neisseria meningitidis. Culture in Fe3+-dicitrate rich medium did not induce subsequent Fe3+-dicitrate binding as it does for Escherichia coli and other bacteria. Growth in iron-restricted conditions slightly stimulated the Fe3+-dicitrate binding system in all the strains studied. Total binding of citrate as Fe3+-dicitrate was 2.5 times that of citrate in the absence of iron. Affinity for Fe3+-dicitrate ranged from 6.3×104 to 2.6×105l/mol, and the number of receptors per cell ranged from 8, 500 to 64, 800. The binding system was highly specific for Fe3+-dicitrate (it did not bind other iron complexes with isocitrate, lactate, pyruvate or EDDA). Fe uptake efficiency was significatively higher in the case strains but, due to the higher number of receptors per cell in the carrier strains, the resulting iron uptake rate is similar in both groups.
Escherichia coli cells exhibited osmotolerance and grew well even in hyperosmotic medium containing 1.2M NaCl (or 2.0M sorbitol) if they had been previously exposed to moderate osmotic stress for a short time (30min). Untreated cells showed repressed growth. This acquirement of osmotolerance against hyperosmolarity was dependent on the concentration of the osmoticum in the osmotic stress conditioning. The most effective conditioning occurred when almost the same moderate osmolarity of electrolytes (about 0.4-0.6M NaCl or KCl) and non-electrolytes (about 0.8-1.2M sorbitol or sucrose) was used as osmoticum. The acquired osmotolerance could be inhibited markedly by chloramphenicol or rifampicin, but not by nalidixic acid. Experiments with 35S-methionine incorporation suggest that the synthesis of several proteins might be related to the acquiring of osmotolerance.
Calmodulin (CaM) was purified from Fusarium oxysporum f. sp. lini SUF 402, to apparent homogeneity as judged by Tricine-SDS-polyacrylamide gel electrophoresis. Molecular mass of the isolated CaM was 18kDa and its pI was pH 4.6. Fusarium CaM had functions as an activator of rat Ca2+-dependent cAMP phosphodiesterase, chicken myosin light chain kinase, and rat Ca2+/CaM-dependent protein kinase II. The amino acid composition of Fusarium CaM was similar to those of other fungal CaM.
A Bacillus sp. strain isolated from termite (Odontotermes obesus) mount soils was found to produce extracellular carboxymethyl cellulase (CMCase). For further characterization the enzyme was isolated and purified from the culture supernatant. It revealed a molecular weight around 250kDa and a tetrameric structure, with a molecular weight of the subunits around 62kDa. Only one type of subunit was found. The enzyme was active over a wide range of conditions (30°C to 65°C; pH 3.0 to pH 11.0). Highest enzyme activity was measured at 50°C and a pH of 6.0. The enzyme was found to be not glycosylated. Glucose and cellobiose, the low molecular weight degradation products produced by the enzyme, did not induce or repress enzyme synthesis. A polyclonal antiserum was raised against the purified enzyme and applied for studies on the cellular location of the enzyme prior to secretion into the culture medium. The enzyme was shown to be located within the cytoplasm and at the cell periphery.