Studies on the Fire-Blight Organism, Bacillus amylovorus 15 



(1927:10) says: "There is first a slight, probably toxic plasmolysis, 

 followed finally by the complete collapse of the protoplast but never 

 its dissolution. ' ' 



The characteristic color and external appearance of blighted twigs 

 and limbs of apple and pear trees, and the lack of similar symptoms 

 when twigs of these same trees are killed by other organisms, has led 

 some pathologists to think that a toxic or an enzymic substance is 

 present in blighted shoots. Whether this substance is excreted by the 

 causal organism or is a decomposition product, has received little con- 

 sideration, but the question merits attention. Bachmann (1913:11) 

 suggests this possibility. 



The writer, in an effort to demonstrate the presence or absence of a 

 definite toxic substance in blighted fruits, placed green Bartlett pears 

 about one and one-half inches in diameter in large, sterile, moist 

 chambers (after sterilizing with bichloride of mercury). The fruits 

 were inoculated with a forty-eight-hours bouillon culture of B. amy- 

 lovorus by means of a hypodermic needle. After inoculation the fruits 

 were again sterilized with bichloride of mercury for five minutes, and 

 were then rinsed three or four times with sterile distilled water. Fruits 

 treated in this way remained free from contaminating organisms in a 

 large majority of cases. 



From ten to fourteen days after inoculation, the fire-blight bacteria 

 had invaded practically the entire fruit, and large drops of milky ooze 

 were exuding from many points and especially from the wounds made 

 during inoculation. The fruits were ground in a food chopper at this 

 time, the parts not invaded by the bacteria being excluded. To a liter 

 of pulp, 100 cubic centimeters of sterile distilled water was added, and 

 the juice was extracted by squeezing through cheesecloth. A portion of 

 (he extracted juice was centrifuged for thirty minutes at 2000 revolu- 

 tions per minute, and was then filtered through filter paper. The remain- 

 ing portion of juice was filtered through cotton to remove some of the 

 organic matter. Subsequent reactions showed little or no difference in 

 the two methods of filtering. 



The juice from healthy green pears was expressed and used as a 

 check, being treated in every respect similarly to that from blighted 

 pears! The juice from both blighted fruits and check (healthy green 

 pears) was placed in test tubes in 10-cubic-centimeter quantities, four 

 tubes being used for each lot, and was treated as Follows: to lot 1, a 

 crystal of phenol about the size of hall' ;i pea was added; to lot 2, a 

 crystal the size of a whole pea; to lot '■'>. 0.5 cubic centimeter of chloro- 

 form; to lot 4, 1 cubic centimeter of chloroform; to lot 5, 2 cubic centi- 

 meters of chloroform; to lot (i, 0.1 cubic centimeter of toluol; to lot 7, 



