BACTERIOLYSIS 53 



EFFECT OF EXTERNAL PHYSICAL CONDITIONS 



The presence or absence of oxygen has no effect upon the course 

 of the phenomenon. The rapidity of multiplication of the ultra- 

 microbes and the duration of the lytic process are the same in 

 aerobiosis as in anaerobiosis. 



On the other hand, as would naturally be expected, the effect 

 of the temperature is marked. 



Experiment XI. Three tubes containing a suspension of the Shiga bacil- 

 lus are inoculated, each tube receiving 0.00,000,01 cc. of the bacteriophage 

 culture. These tubes are placed at different temperatures; the first at 8, 

 the second at 22, and the third at 37C. 



The suspension held at 8C. shows no lysis after twenty-four hours, but 

 after 15 to 16 days lysis is complete. The number of ultramicrobial ele- 

 ments at this time is 180,000,000 per cc. as compared with 20 to 25 per cc. 

 when they were introduced. 



The suspension kept at 22C. shows that multiplication commences after 

 three hours. At this time the count is 75 ultramicrobes per cubic centi- 

 meter. After five hours the count is 8,000, after eight hours 190,000, and 

 at twenty-five hours lysis is complete and the count is 780,000,000 per cubic 

 centimeter. 



The suspension held et 37C. shows 210 ultramicrobes after two hours, 

 10,000 after three and one-half hours, 200,000 after five hours, and 

 1,700,000,000 per cubic centimeter after thirteen hours, with a complete 

 lysis. 



Between 37 and 41C. the course of the reaction does not show 

 appreciable variation. Between 41 and 44C. the lysis is less 

 and less complete. For this there are two reasons; the develop- 

 ment of the ultramicrobes is less and less active, and the number 

 of bacilli killed in consequence of the elevation of temperature 

 is greater and greater. As a result the number of organisms ca- 

 pable of being attacked and dissolved are less and less numerous. 

 However, serial cultivation of the bacteriophage at 44C. is still 

 possible. The ultramicrobe can be cultivated at temperatures 

 higher than those supported by B. dysenteriae. With the latter 

 growth ceases at 43C. 



In effect, the optimum temperature for the bacteriophage is 

 the same as that for the bacterium, as is but logical, since all 

 experimental work demonstrates that the more closely the bac- 

 terial cell approaches normal so much the better is it attacked. 



