THE NUMBER OF GENERATIONS NECESSARY FOR THE DEVELOPMENT OF THE POWER OF AEROBIC GROWTH BY BACTERIUM ABORTUS (BANG)

It is a well known fact that the Bang bacterium when 6,rst isolated does not grow readily in the presence of air. The employment of B. subtilis as an agent in the production of partial anaerobiosis was found to be necessary in growing this organism until several generations have passed. A glass jar may be used from which the air ca,n be partly exhausted with a suction pump but we prefer in this laboratory the use of B. subtilis which is the cultural method of Nowak of Austria (1908). This method consists in lowering the pressure of oxygen to that necessary for the growth of the abortion bacterium by means of the Bacillus subtilis, allowing 1 sq. cm. of surface culture of the B. subtilis to each 15 cc. capacity of the sealed jar in which it is grown. The technique usually employed is to streak the contaminat-ing material over two or three Petri dishes in succession, as is ordinarily done in making streak dilutions. The plates are then incubated at 37°C. for twenty-four hours in the air to allow contaminating organisms to develop. The colonies are then marked with a wax pencil or India ink and the plates transferred. to the Novy jar and incubated for three days, as indicated above. At the end of this time the transparent colonies of Bact. abortus (Bang), if present, may appear on the clear spaces. In our studies to determine the number of generations it takes to grow this organism in air, we incubated the plates in air for three days to give the Bact. abortus (Bang) ample time to grow.