Effect of dicumarol on the growth of some soil microorganisms.

The effect of dicumarol on growth of selected soil bacteria: Azotobacter chroococcum, Arthrobacter globiformis, A. citreus and Bacillus megaterium was studied. The following minimum concentrations were inhibitory in vitro: Arthrobacter citreus--20 mug/ml., Bacillus megaterium--40 mug/ml., Azotobacter chroococcum--40 mug/ml. Arthrobacter globiformis--70 mug/ml. Cells of all microorganisms studied grown in the presence of dicumarol developed aberrant morphological forms.     

Measurement of phosphate concentration in the presence of very labile phosphate esters

There are a number of methods available for the measurement of phosphate ion concentration, which may be used when moderately labile phosphate esters such as ATP are present in low concentration. However, the highly acidic conditions usually employed make these unsuitable when very labile esters such as phosphocreatine are present. A method in which the phosphomolybdate complex is developed under mildly acidic conditions, using high molybdate concentrations to counteract the reduced assay sensitivity at high pH, is described. The assay is linear in the range 5-300 microM phosphate, and micromolar concentrations of phosphate can be reliably measured in the presence of millimolar phosphocreatine.     

Detection and study of the labile toxic factor of Proteus mirabilis]

The author studied the dynamics of toxin formation of the high- and low-virulent Pr. mirabilis strains. The high-virulent strain produced toxic substances of the exotoxin type detectable in 1-2-day broth cultures. Later the activity of the culture medium of both cultures under study was due to substances of the endotoxin type. By physico-chemical and immunobiological properties, and also by chemical composition of Pr. mirabilis "early toxin" was similar to the exoenterotoxins of enterobacteria. A principal possibility of concentration and purification of Pr. mirabilis "early toxin" with the use of ultrafiltration and gel-chromatography was demonstrated.