Abstract
Aqueous suspensions of Esch. coli picked from 24-hour growths at 37.5°C. on Bacto-nutrient agar adjusted in pH from 6.2 to 7.9 gave slightly lesser (to 4%) cataphoretic velocities, as measured in Falk capillary cells 1 than did suspensions washed one to 3 times. Accordingly, we used a suspension produced by washing the growth from the medium, centrifuging once and resuspending the bacteria in distilled water, in a study of the effect of the addition of salts to the growth medium on the electrophoretic velocity of Esch. coli as measured with the Falk capillary cell. As Table I will show, the addition of the salts to the growth medium had little or no effect on the cataphoretic velocity which measures the zeta potential. In a future paper (Pedlow and Lisse) it will be shown that the zeta potential of the bacteria in aqueous suspension can be changed when salts are added to the growth medium in greater concentrations.
It was also shown that no change of the electrophoretic velocity of organisms (once washed) greater than 2.5% was produced by adjusting the initial pH of the medium to values over the range 6.8 ± 1.9, the pH after growth having a value 6.5 to 8.6, 5.7 to 8.6, and 6.1 to 8.6 for the upper half, lower half and the whole agar.
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