. Diseases of bees. Bees. Apr. 12,1024 Development of American Foulbrood 141 CUANTITATIVE GROWTH IN PLATE CULTUBE8 Great difficulty is found in obtaining satisfactory plate cultures. Only two series of plate cultures were obtained which could be counted successfully. The average number of colonies showed a definite decrease with increased sugar concentration, with no growth at 3 per cent or higher. (Table II, fig. 10). As stated above, the plate method, with the small amount of initial inoculum necessary for accurate counts, is not a satisfactory method for obtaining growth of Bacillus larvae
. Diseases of bees. Bees. Apr. 12,1024 Development of American Foulbrood 141 CUANTITATIVE GROWTH IN PLATE CULTUBE8 Great difficulty is found in obtaining satisfactory plate cultures. Only two series of plate cultures were obtained which could be counted successfully. The average number of colonies showed a definite decrease with increased sugar concentration, with no growth at 3 per cent or higher. (Table II, fig. 10). As stated above, the plate method, with the small amount of initial inoculum necessary for accurate counts, is not a satisfactory method for obtaining growth of Bacillus larvae under these conditions, although the method may be used for obtaining pure cultures. From these observations (Table I) it is, therefore, safe to conclude that a con- centration of reducing sugar of approximately 3 to 4 per cent or more inhibits the growth of Bacillus larvae, although slight germination of spores may take place at higher sugar /.O AS PER CSA/r DEXTROSE Fig. 10.—Average number of colonies per 4-min. loopful of vegetative culture suspension witli varying suga r concentration (Table II) QUANTJTATIVE DETERMINATION OF UNASSIMILATED SUGAR IN THE LARVAL INTESTINE AT VARIOUS AGE PERIODS In the preliminary experiments it was shown that unassimilated sugar is present in the intestinal contents of the actively feeding larva, which apparently i s assimilated completely by the time the prepupa has extended in the cell and has become quiescent. Since it is demonstrated that a direct relation exists between the growth of Bacillus larvae in suitable culture media and its reducing sugar con- centration, it is now necessary to determine quantitatively the amount of unas- similated sugar in the intestine of the feeding larva and in the intestine of the prepupa, in order to determine whether reducing sugar concentration has any bearing on the time of attack by American foulbrood. COMPOSITION OF BROOD FOOD The older bee larvae {40) receive a food c
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