670 



FLOCCULATION OF BACTERIA BY PROTEINS 



(1921) has also found Bacterium coli to agglutinate with acids in the 

 absence of salt. The strain with which most of our work was done 

 underwent a curious mutation about 2 months after it was first 

 isolated. Our records show that on December 11 no agglutination 

 took place in any of the acetate or lactate buffer m^ixtures; 3 days 

 later the organism, with all its other characteristics unchanged, was 

 found to agglutinate at pH 3.2 (negative at 3.0 and 3.5), both in the 

 acetate and lactate buffer mixtures, but not in the phthalate buffers of 

 Clark and Lubs (1917). No further change has been observed to the 

 present time. 



In all of these experiments, Bacterium coli was grown on beef extract 

 peptone agar plates. The growth was suspended in 0.85 per cent 

 NaCl, filtered through paper, centrif ugated , then centrifugated three 

 times out of distilled water. In most of the experiments, a tempera- 

 ture of 40°C. was employed. Flocculation was observed macro- 

 scopically; no test was considered positive unless definite macroscopic 

 flocks were formed, which settled out to leave a clear supernatant fluid. 



Lactic Acid-Sodium Lactate Biiffer Mixture. 



Acetic Acid-Sodium Acetate Buffer Mixtures. 



