250 GENERAL MICROBIOLOGY 



Owing to the presence of some carbon-monoxide in the 

 air of the laboratory from the burning gas, the carbon- 

 monoxide-assimilating B. oligocarbophilus often appears as 

 a dry white skin on the surface of the solution in these flasks. 



Note. Solution I is adapted for relatively increasing the nitrite 

 bacteria, Solution II the nitrate producers and Solution III the sim- 

 ultaneous growth of both organisms as in nature. 



3. After eight to fourteen days, test all solutions and 

 control flasks every second or third day by transferring 

 0.1 c.c. with a sterile pipette to a white glazed surface 

 (e.g., plate) using 



(a) Nessler's solution, for ammonia; 



(6) nitrite test solutions, for nitrites; 



(c) nitrate test solution, for nitrates. 



Tabulate your results. Discuss and explain the decom- 

 position which is taking place in each inoculated flask, 

 giving the successive steps in the disintegration of the 

 crude nitrogenous organic matter. 



4. Examine a loopful of each solution in the hanging 

 drop each time chemical tests are made. Morphologically 

 what types predominate in each solution? In the sample 

 of soil? Of manure? Are any of these spore-formers? 

 If so, which type? 



5. Make permanent stained preparations from each 

 flask. 



6. Nitrifying bacteria do not grow on the ordinary 

 solid media. Why? Many different methods have been 

 tried for the isolation of nitrifying organisms but the obtain- 

 ing of pure cultures is still a most difficult bacteriological 

 task. 



(See appendix for media used for the isolation of these 

 organisms.) 



What methods are employed for their isolation besides 

 the use of solid synthetic media? What is the principle 

 of each method? 



What are the different types of nitrifying organisms? 



