Studies on the Fire-Blight Organism, Bacillus amylovorus 27 



Arbutin is the predominant glucoside in pear shoots according to 

 Lincoln (1926). Phloridzin, the principal glucoside in apple, is found 

 also in plum, sweet cherry, and probably Spiraea, Crataegus, and 

 Amelanchier according to Harvey (1925). Harvey shows a rather close 

 correlation between rapidity of growth and arbutin and phloridzin con- 

 tent in the pear and apple shoots. This may have a direct bearing on 

 susceptibility to infection by B. amylovorus. Whether or not the fire- 

 blight organism can hydrolyze phloridzin remains to be demonstrated, 

 but the evidence is at least suggestive. 



„, . Protease 



Trypsin 



Blood fibrin was stained with 1 per cent of congo red, boiled in water 

 to fix the color, and then autoclavecl with Uschinsky's solution without 

 glycerin. Some color was released by the autoclaving. The colored 

 solution was decanted, sterile solution was added, and, after incubating 

 for forty-eight hours to test for sterility, eight of the sixteen tubes were 

 inoculated and the remainder were reserved as checks. Growth of the 

 cultures for three weeks failed to show any digestion of the fibrin with 

 a resultant release of red color. This would indicate that Bacillus 

 amylovorus did not produce trypsin in these tests. 



Summary on enzymes 



Summing up the writer's work on the enzymes produced by Bacillus 

 amylovorus, the following were found: sucrase, or invertase, maltase, 

 inulase, and arbutase. Tests for amylase, pectosinase, pectase, pec- 

 tinase, eellulase, amygdalase, and trypsin failed to give positive results. 

 These tests do not, of course, demonstrate the inability of B. amylovorus 

 to produce any or all of the latter group of enzymes. Different meth- 

 ods may show later that the enzymes were merely inhibited in formation 

 or inactivated in these experiments. 



longevity of the organism 



Difference of opinion exists among pathologists as to the ability of 

 Bacillus amylovorus to withstand adverse conditions. Both D. H. 

 Jones (1909) and Stewart (1913) found that drying for five days 

 on a cover glass did not kill the organism. However, Stewart obtained 

 no growth after seven days in bouillon from organisms so treated. In 

 attempting to solve the problem of rapid dissemination of B. amylovorus 

 in an orchard, Gossard and Walton (1922), of Ohio, showed that the 

 organism can live in honey for seventy-two hours or more, in aphid 

 lioneydew for seven to len days if moisture is supplied, and in nectar 

 of peach, plum, and cherry, for five days or longer. The last-mentioned 

 fact is not surprising, as both plum and cherry have been proved to 



