Studies on the Fire-Blight Organism, Bacillus amylovorus 19 



with apple shoots immediately. Others were allowed to stand for three 

 or four days after being treated, so that the bacteria would lyse and 

 thus release any endotoxins which might be produced. None were 

 found. 



The plasmolytic action, or the effect of concentration of the juice 

 from blighted pear and that of the diffusate of such juice, was tested 

 on sections of young green apple stems, leaves, and fruit. The colored 

 epidermal cells of Tradescanfia zebrina were used also. It was found 

 that little or no plasmolysis occurred except when the juice was highly 

 concentrated. The diffusate caused no marked plasmolysis on any of 

 the tissues tested. This would indicate that the wilting and drooping, 

 with the resultant blackening of stems and leaves, was not the result 

 of too high an osmotic pressure in the pear sap. Even though the 

 wilting and drooping was caused by water loss, the blackening of the 

 stems and leaves could not be explained on this basis. 



The property of being precipitated by alcohol would class this sub- 

 stance as being similar in nature to the true bacterial toxins and 

 enzymes. It may be, however, that the toxin is precipitated by being 

 adsorbed by other organic matter, since the amount of organic matter 

 precipitated is rather large at the lower concentration of alcohol, 65 

 per cent. At the higher concentration of alcohol, 85 per cent, the 

 precipitate is finely divided and is small in quantity, being just sufficient 

 to make the solution turbid. 



If the toxic principle contained in juice from blighted pears is in 

 the nature of a true bacterial toxin, one would expect it to dialyze 

 through a thin, but not through a thick, membrane ; this was shown 

 to be the case. Also, it should be thermolabile ; it appears to be ther- 

 mostable. Exposure to the air for fourteen hours did not noticeably 

 inactivate, the toxic principle ; it should have done so. The toxic 

 principle, therefore, may be either an endotoxin or a decomposition 

 product of the host cells. Yet, when lysis of the bacterial cells was 

 produced by heat or by germicides, none of the many artificial cultures 

 in which the organism was grown gave the slightest indication of being 

 toxic for green apple shoots. Also, the sap from green pear fruits 

 rotted by other organisms, failed to cause wilting of apple terminals. 

 Such indirect tests serve to characterize the toxic principle, hut its real 

 physical and chemical constitution remains to be determined. 



PRODUCTION OF ENZYMES 



Microorganisms, both fungi and bacteria, have been shown to be 

 active in the production of enzymes. For a complete review of this 

 subject and the nature of enzyme action, such works as those of Haas 



