Microbial Structures and Staining Reactions 115 



difficult to demonstrate the actual spore, but the resistance of a 

 culture to 80° C. for 10 minutes suggests the presence of spore- 

 forming organisms or the presence of cells that are unusually 

 resistant to heat. 



FLAGELLA STAINS 



Before attempting to demonstrate flagella by staining reactions, 

 the culture must be grown under conditions optimum for the en- 

 couragement of the formation of these structures. One theory, 

 which in practice has been shown to possess considerable merit, 

 is to make the organism go hunting for food in a large tube of 

 distilled water after the bacteria have been grown in the conden- 

 sation water of an agar slant and serially transferred each twenty- 

 four hour period for several days. By dashing about in the dis- 

 tilled water in search of food, development of flagella is theoret- 

 ically encouraged. Some persons, on the other hand, believe it is 

 the slow growth or static condition of the cultures which permits 

 development of flagella to take place. Flagella apparently become 

 thicker and longer with age and are more readily stained than 

 when they are in the active stages of their development. By treat- 

 ing the dry film on the slide with a mordant (a complex colloidal 

 solution), the diameter of the flagella is built up to within micro- 

 scope range by the packing-on of mordant. Subsequent staining 

 with either methylene blue or carbol fuchsin will usually reveal 

 the thread-like flagella, particularly at the edge of the stained 

 smear. Strict attention to details is of the utmost importance in 

 this delicate staining procedure, and scrupulously clean slides free 

 of scratches are essential. The presence of even minute amounts 

 of organic matter interferes with good staining, because the debris 

 may react with the mordant and absorb some of the dye. 



The discussion of staining and staining technics in this chapter 

 has been brief. Definite procedural details vary so greatly from 

 one laboratory to another that it seems wise to leave the fine de- 

 tails of specific staining to the individual instructors as part of 

 their lecture or laboratory discussions. 



