STUDIES ON SALT ACTION
Ih an earlier paper (Falk, 1923) our present state of knowledge in regard to the physiological influence of mineral salts upon bacteria has been somewhat comprehensively reviewed. The experiments here reported were designed to determine with some exactness the effect upon bacterial viability of sodium and calcium chlorides, alone and in combination. Our work has extended over a long period, the first preliminary communications (Winslow and Falk, 1918) having been made over four years ago. The early experiments at times yielded conflicting results and it was only by a careful study of the hydrogen ion factor (Falk, 1920) that we succeeded in explaining these inconsistencies along the lines since so well worked out for problems of bacterial growth by Holm and Sherman (1921) and Sherman and Holm (1922). The study presented here deals with the viability of Bactenium coli in distilled water, in various concentrations of NaCl, and in various concentrations of CaCl2 with varying hydrogen ion concentrations for each solution; while a following paper (IJX) deals with viability in various mixtures of the two salts mentioned above.
THE FLOCCULATION OF BACTERIA BY PROTEINS
1. The effect of adding pure proteins to bacterial suspensions at different H ion concentrations has been studied. 2. The zone of flocculation of protein-treated bacteria bears a significant relationship to the isoelectric point of the protein used. With the higher concentration of protein, agglutination occurs at or near the isoelectric point of that protein; at reactions acid to this, the bacteria carry a positive charge and are not agglutinated. With diminishing concentration of protein, the zone of flocculation shifts toward and goes beyond that characteristic of the untreated bacteria. This occurs both in the presence and absence of salts. 3. A diversity of other suspensions, such as sols of gold, mastic, cellulose nitrate, cellulose acetate, Fe(OH)3, oil emulsions, and erythrocytes, have been found by ourselves and others to exhibit a similar altered stability when treated with proteins in the same way.
Secoiridoids from Olea europaea
Abstract Three new secoiridoids have been isolated from the leaves of Olea europaea along with the previously reported. The compounds were identified by spectral means.