A limnological reconnaissance of Lake Tebenquiche,Salar de Atacama,Chile

A number of expeditions to the area of Salar de Atacama, Chile, 68° 15'W, 20° 30'S, have involved studies of the biological and chemical features of Lake Tebenquiche, situated in the interior of the salar. Chemically, Tebenquiche is hypersaline, with practically anoxic waters dominated by sodium and chloride ions but with high concentrations of sulphate also. The lake is surrounded and invaded by macrophytes, dominated by Scirpus olmeyi and Juncus, which provide organic material for the formation of bacterial mats. The fauna of limnetic crustaceans is almost exclusively of Artemia salina. The most important genera of bacteria are: Marinomonas, Halobacterium, Acinetobacter and the sulphur reductors Vibrio and Bacillus. The Cyanobacteria are represented exclusively by Oscillatoria.     

Trypanosoma cruzi: defined medium for continuous cultivation of virulent parasites.

A liquid medium was developed for the continuous cultivation of Trypanosoma cruzi. Among the several highly purified macromolecules tested only bovine liver catalase, horseradish peroxidase, lactoperoxidase, and bovine hemoglobin supported the continuous growth, at high yield, of mice-virulent Trypanosoma cruzi; other hemoproteins were inactive. Bovine liver catalase showed optimal Trypanosoma cruzi growth-promoting activity, parasites reaching 20 × 10⁶ parasites/ml (95% epimastigotes) at about 10 days in most of the 45 subpassages to date. Furthermore, this protein in the incubation medium provided all the amino acid requirements of actively growing parasites, thus eliminating the need for exogeneous free amino acids. Additional experiments revealed that the hemoprotein's growth-promoting activity was independent of any enzymatic activity and that reconstituting the exact protein composition by means of exogeneous amino acids did not support parasite multiplication, suggesting the importance of the primary structure of the active proteins for growth-promoting activity. These active macromolecules supported the multiplication of five different strains of Trypanosoma cruzi, but did not support Leishmania brasiliensis or Leishmania mexicana proliferation, suggesting species specificity.     

Ferritin intestinal absorption.

Ferritin as a source of iron was consiered. A good iron absorption rate appears in normal rats with an in vivo absorption technique. The same absorption appears in iron-deficient animals. The iron stored in intestinal wall is lower in anemic rats than in normal ones, suggesting a higher draw of iron from lumen to blood.     

Determination of intermediary metabolites in yeast. Critical examination of the effect of sampling conditions and recommendations for obtaining true levels

Summary The effect of sampling conditions on the levels of adenine nucleotides, pyridine nucleotides, glycolytic intermediates and related metabolites in yeast has been studied. A systematic examination of the conditions for harvesting has shown that it can be best accomplished by rapid filtration. Delays in the handling for removal of the medium, as is usual in the process of obtaining a number of data reported in the literature, lead to important changes in some of the metabolites examined. It is also shown that when a washing is imperative it can be carried out with a methanol-water mixture (50/50, v/v) cooled at –40° without loss of intracellular concentrations of non-readily diffusible metabolites.On the basis of this experience the outline of a generally applicable procedure is presented.     

Micrococcus lysodeikticus membrane ATPase. effect of trypsin on stimulation of a purified form of the enzyme and identification of its natural inhibitor

A soluble purified form of Micrococcus lysodeikticus ATPase (form B_AT, from strain B, active, trypsin-stimulated) was stimulated 100% by trypsin and this stimulation was inhibited by preincubation of the protease with phenyl methyl sulphonylfluoride. This form of the enzyme was also stimulated 125–150% by filtration on Sephadex G-200. Analysis by sodium dodecyl sulphate-gel electrophoresis showed that stimulation of this form of M. lysodeikticus ATPase was always accompanied by the disappearance of a subunit of mol. wt. 25 000 (ε subunit). It suggests that this subunit is the natural inhibitor of M. lysodeikticus ATPase. In the case of ATPase stimulation by trypsin, a partial and limited degradation of the α subunit was also observed. The interaction between the ε subunit and the rest of the ATPase complex was reversibly affected by pH, suggesting its non-covalent nature.     

Permeabilization and lysis induced by bacteriocins and its effect on aldehyde formation by Lactococcus lactis

Permeabilization induced by lacticin 3147, lactococcins A, B and M, enterocin AS-48 and nisin, bacteriocins described as cell membrane-pore forming and lytic agents, enhanced in all cases aldehyde formation by Lactococcus lactis IFPL730. Nevertheless, the conversion of isoleucine into 2-methylbutyraldehyde depended not only on the degree of permeabilization but also on the bacteriocin that caused the cell membrane damage. The highest values of 2-methylbutyraldehyde corresponded to cell suspensions containing lacticin 3147 and lactococcins, treatments that provoked further lysis in addition to induced permeabilization.