Relations between pH,Agglutination and P. D. with Bacterium Phaseoli Sojense.

Abstract

In the course of a series of studies on a group of bacteria pathogenic for plants, it was found that a strain of Bacterium phaseoli sojense, when plated on agar, gave colonies that were distinctly “Rough” and “Smooth”. The cultural characteristics, virulence for plants and the serological reactions of these organisms have been described elsewhere. 1 We were interested in studying the agglutination reactions of these cultures, particularly because the “Rough” organisms, although more agglutinable than the “Smooth”, as is generally the case, had also been found to be spontaneously agglutinated even in distilled water suspensions and after repeated washings with water.

In Table I we present the results of agglutination and P. D. (electrophoretic potential difference) measurements on suspensions prepared in distilled water after three washings with water. 2 Adjustments of pH were made by appropriate additions of aqueous HCl or NaOH solutions to the specified pH values.

From an inspection of the data in Table I it appears that:

1 The “Rough” strain is, and the “Smooth” strain is not spontaneously agglutinable in distilled water.

2 Both strains showed marked acid agglutination.

3 Only the “Rough” showed alkali agglutination.

4 In the acidulated solution there is correlation between the effects of acidulation upon agglutination and upon reduction of the negative P. D. to approximately zero (isoelectric) or to slightly positive values.

5 There is no definite correlation between P. D. and agglutination in alkaline solutions.

6 The “critical” potentials are different for the “Rough” and “Smooth” strains.