Clear Media for the Recovery of Pasteurella tularensis

Peptic digests of blood and hemoglobin were investigated as substitutes for the blood used in the preparation of glucose-cysteine-blood agar plating medium for the recovery of the virulent Schu strain of Pasteurella tularensis. Digest media so prepared were found to be satisfactory for the quantitative recovery of freshly grown cells but not for cells stored longer than several days. The addition of appropriate quantities of human plasma, bovine sera, or soluble starch rendered the digest media appropriate for use with stored cultures. The peptic digest-plasma (PDP) and peptic digest-starch (PDS) media were evaluated and found satisfactory for the quantitative recovery of P. tularensis Schu from freshly prepared and stored cultures, and from aerosols produced therefrom. With cultures stored longer than 6 weeks, the starch modification (PDS) was not as satisfactory as, and the plasma variation (PDP) was better than, glucose-cysteine-blood agar (GCBA) for the recovery of the organisms. PDP was superior to either GCBA or PDS medium for the recovery of the weakly virulent Jap 4 and Niieg-blue strains of P. tularensis.     

Harvesting of Algae by Froth Flotation

A highly efficient froth flotation procedure has been developed for harvesting algae from dilute suspensions. The method does not depend upon the addition of flotants. Harvesting is carried out in a long column containing the feed solution which is aerated from below. A stable column of foam is produced and harvested from a side arm near the top of the column.

The cell concentration of the harvest is a function of pH, aeration rate, aerator porosity, feed concentration, and height of foam in the harvesting column. The economic aspects of this process seem favorable for mass harvesting of algae for food or other purposes.