The alkaline isopotential point of the bacterial cell. Preliminary note. 1

Earlier studies on the electrophoretic migration of bacterial cells suggested the probable existence of a second isopotential point in the extreme alkaline range but results were irregular and uncertain. 2 Later work shows that such inconsistencies are due to a phenomenon observed in another connection, 3 the creation through the buffering power of the bacteria of zones of diminished alkalinity in their immediate vicinity. This effect can be eliminated by shaking the suspension vigorously for five minutes before placing it in the electrophoretic cell.

Observations made in this way, and with electrometric determination of pH, 4 show that there is a very definite alkaline isopotential point close to pH 13.5,—that for B. cereus lying at about 13.3 to 13.4 and that for Bact. coli at 13.6 to 13.8. Above this isopotential point the cells acquire a positive charge which increases rapidly to very high values with further increase in alkalinity.