GEORGE K. K. LINK 599 



vestigated further. Kotila and Coons' made a casual determination of the effect of 

 dosage upon infection by B. atrosepticiis and found that smaller dosages required long- 

 er time and also failed more frequently to produce infection. They found further that 

 whereas larger dosages of this organism cause dissolution of potato-tuber tissue and 

 necrosis of the cells, smaller dosages cause only hypertrophy. The latter observation 

 is in harmony with data relative to the legume-nodule organisms, which when inoc- 

 ulated in large numbers may kill the host cells at once, but when inoculated in 

 smaller numbers first cause hypertrophy. 



Virulence and electro phoretic potential in rough and smooth cultures. — Following 

 the work of Falk, Gussin, and Jacobson,^ Sharps and Falk, Sharp, and Link^ made 

 measurements of the electrophoretic potential on smooth and rough cultures of Bad. 

 phaseoli sojense. A direct correlation was found between virulence and electro- 

 phoretic potential in acid, but not in alkaline menstrua. 



Serological characteristics of normal and abnormal colonies. — Sharps did not find 

 any difference between the antigenic properties of S and R strains of Bad. phaseoli 

 sojense in their reaction against suspensions of the S strain and heterologous organisms. 

 He was not able to make tests against suspensions of the R strain because the organism 

 agglutinated spontaneously in 0.85 per centNaCl and in distilled water. Link and Link'' 

 were able to get a suspension of the rough strain, and were thus able to test the anti- 

 serum of Bad. phaseoli sojense R against homologous and heterologous suspensions of 

 organisms. Their findings indicate that there is no serological difference between the 

 rough and smooth strains of Bad. phaseoli sojense. These authors, in agglutination 

 studies on eleven plant pathogens, obtained surprising results with Bad. tumefaciens. 

 The culture used in the tests was one which was partly smooth and partly rough. 

 The spontaneously agglutinable fraction was allowed to settle out after three wash- 

 ings in saline solution and centrifugation. After standing twelve hours, the suspen- 

 sion was centrifugated at low speed. Apparently all the rough elements had been re- 

 moved, because there was no more spontaneous agglutination or settling out. When 

 the antiserum of the mixed culture was tested against the suspension of the homol- 

 ogous organism freed of the spontaneously agglutinating (R) element, agglutination 

 was obtained in titres of 1-10,240, and cross-agglutination was obtained in dilution 

 1-80 with only one of the ten organisms tested. In other words, the test was specific. 

 However, when heterologous antisera were tested against the suspension of Bad. 

 tumefaciens, cross-agglutination was obtained in all cases. Curiously enough, in one 

 instance the antiserum of one of a pair of animals immunized with one organism gave 

 agglutination whereas that from the second animal failed to agglutinate Bad. tume- 

 faciens. Apparently we have a case of specific agglutination when Bad. tumefaciens 



' Kotila, J. E., and Coons, G. H.: "Investigations on the Blackleg Disease of Potato," Michigan 

 Agr. Exper. Sta. Tech. Bull. 67, 1925. 



^ Falk, I. S., Gussin, H. A., Jacobson, M. A.: "Studies on Respiratory Diseases: XXI. Electro- 

 phoretic Potential and Virulence of Pneumococci (tj^jes i, 2, 3, and 4)," /. Infect. Dis., 37, 481. 1925. 



^ Sharp, C. G. : loc. cit. 



■•Falk, I. S., Sharp, C. G., and Link, George K. K.: "Relations between pH, Agglutination and 

 P.D. with Bacterium phaseoli sojense," Proc. Soc. Exper. Biol. 6° Med., 1927. 



s Sharp, C. G.: loc. cit. ^ Link, George K. K. and A. DeS.: loc. cit. 



