6oo BACTERIA IN RELATION TO PLANT DISEASES 



is used as antigen, but cross-agglutination when the antisera of other pathogens are 

 tested against suspensions of Bad. tumejaciens. 



Spontaneous agglutination of plant pathogens. — Berridge' found that chemical 

 agglutination tests are as reliable as serum agglutination tests for certain soft-rot 

 bacteria. The phytopathological literature contains casual references to instances of 

 self-flocculation of plant pathogens. Sharps found that the R strain of Bad. phaseoU 

 sojense agglutinated spontaneously in distilled water even after nine washings, and 

 also in 0.85 per cent NaCl. Link and Link-' were able to get a permanent suspension 

 of this organism by taking up the original flocculum in 0.85 per cent NaCl and 

 washing and centrifugating it three times. Sharp reports that Bad. phaseoli sojense 

 (R) agglutinates through practically the entire range of pH 2.0-9.4, little or no 

 agglutination occurring from pH 5.5-5.8. The S strain agglutinated only between 

 pH 1.2-4.0. Sharps and Falk, Sharp, and Link^ found further that in the acid zone 

 there seemed to be a correlation between low P.D. (electrophoretic potential differ- 

 ence) and high agglutinability, and between high P.D. and low agglutinabihty for 

 both the S and the R strains, but not in the alkaline range. 



Sharp found that Bad. phaseoli sojense (S) produced a scaly pellicle in lactose and 

 levulose broth, whereas Bact. phaseoli sojense (R) produced a very heavy granular pre- 

 cipitate in nearly all sugar broths tested. 



Link and Link-* and Link and Hull^ report that their strain of Bad. tumefaciens 

 which develops colonies that are rough at first, and become smooth when suspended 

 in 0.85 per cent NaCl or distilled water, always showed spontaneous agglutination 

 for about one-fourth of the suspension. By centrifugation and settling, the two frac- 

 tions could be separated. Link and Hull found also that flocculation or settling 

 out is by no means a qualitative matter associated or correlated with roughness or 

 smoothness. In the first place, the spontaneous flocculum of Bad. phaseoli sojense (R) 

 could be resuspended. Apparently during the time which elapsed between Sharp's and 

 their tests with the same culture, some change toward lesser agglutinabihty had oc- 

 curred in the organism. Furthermore, Bad. citri, which is as rough as Bad. phaseoli 

 sojense and more rough than Bad. tumefaciens, does not agglutinate spontaneously 

 nor does Bad. medicaginis var. phaseolicola, No. 23. It is apparent that the data are 

 still too few and too diverse to warrant any general conclusions, save the one that fur- 

 ther work should be done in this interesting field. 



AUTOLYSIS phenomena: transmissible lytic principle (bacteriophage) 



Smith^ has described and illustrated colonies which suggest the phenomenon of 

 autolysis reported by animal bacteriologists. These are the "windowed" colonies of 

 Bad. malvacearum, and, even more convincingly, the colonies of Bad. translucens 

 var. undulosum with "liquefaction pits." 



' Berridge, Emily M.: "Studies in Bacteriosis." XIV. Ann. Appl. Biol., 13, 12-17. 1926. 



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



3 Link, George K. K. and A. DeS.: loc. cit. 



" Falk, I. S., Sharp, C. G., and Link, George K. K.: loc. cit. 



5 Link, George K. K., and Hull, K.: loc. cit. 



* Smith, E. F.: Bacterial Diseases of Plants. 



