346 



BACTERIA IN RELATION TO PLANT DISEASES. 



This organism does not produce acids in milk, but there is a slowly increasing alka- 

 linity, and after some days (3 to 10 or more) the casein is precipitated as a finely divided, 

 voluminous, mobile mass, which settles slowly. These phenomena are best observed in 

 litmus-milk. The litmus in such cultures is slowly reduced, but on the death of the organism 

 it is oxydized back into a deep blue. In the end the casein is partially peptonized, but this 

 change does not occur rapidly. The organism makes a good growth in milk and forms a 

 bright yellow rim (plate 20, figs. 2-4), and sometimes a pellicle. In old cultures sheaf- 

 like crystals of tyrosin occur. 



In April, 1898, two 10 cc. tubes of milk, which had received 4 steamings and been under 

 observation for a month unchanged, received 200 ings, each of thymol. One was put away 

 as a check, the other received 8 cc. of whey from a milk-culture of Bad. hyacinthi 33 days 

 old, after this had been heated in the water bath for 10 minutes at 51.8 C. (4 above the 

 thermal death point). There was no change in the check tube. In the other, there was 

 copious precipitation of the casein in 48 hours, but no evidence of bacterial growth either 

 then or subsequently (n days). In October, 1898, the experiment was repeated with the 

 same result. In this experiment (fig. 143) 10 cc. of sterile milk received 3 cc. of whey from 



a milk-culture 10 days old. One hour after 

 adding the whey the tube was heated for 20 

 minutes at 52C. in the water bath to destroy 

 the bacteria. In 24 hours the milk was entirely 

 coagulated. A small drop from this tube was 

 now transferred to bouillon but did not cloud 

 it (5 days). At the same time another tube of 

 the same milk received 3 cc. of whey from an- 

 other milk-culture of the same organism, the 

 only difference being that in this case the milk 

 was heated for 10 minutes at 8oC. after adding 

 the whey: This, to destroy the supposed enzyme. 

 Result: No change in the milk (7 days). 

 These experiments indicate the presence of a 

 lab ferment. 



In litmus-milk (and in bouillon) contain- 

 ing ethyl alcohol, a volatile acid is formed, and 

 there is a fragrant odor in the steam. Methyl 

 alcohol is not decomposed. 



There is a moderate, smooth, wet-looking 

 growth on steamed potatoes standing in dis- 

 tilled water, but it is not prolonged or copious, 

 the color on potato is at first wax-yellow, but 



after some time it is dulled to a brownish yellow. At 2OC. to 25C. the streak is not visible 

 until the second or third day when inoculations are made from fluids. Growth on potato- 

 cylinders is much increased by the addition of a little cane-sugar, dextrin, or malt-diastase. 

 The action of the organism on starch is feeble, and the water surrounding the potato is 

 never converted into a solid mass of slime as in case of Bad. phaseoli, Bad. camfestre, Bad. 

 juglandis and other starch-destroying organisms. On potato cylinders first soaked in pure 

 water to remove the slight amount of sugar and acids on the cut surface and then tubed, 

 growth did not occur or was delayed and scanty. Young cultures have no smell; in old 

 cultures there is a feeble odor. Type of growth on potato like Bad. stewarti (PI. 17, fig. 2). 



*Fic. 143. Two tubes of sterile milk to which was added equal volumes of whey from old cultures of Bad. 

 hyacinthi in milk. Whey added to tube b after heating to 80 C. (to destroy enzyme); whey added to tube a after 

 heating to 5 2 C. (sufficient to destroy bacteria only). Result: Milk curdled promptly in tubea and remained unchanged 

 in the other. Oct. 1898. 



Fig. 143.* 



