Microbial Structures and Staining Reactions 85 



structures particularly adapted for breathing, digestion, and excre- 

 tion. Bacteria, however, must metabolize and reproduce within 

 the confines of a single microscopic cell. It appears that reproduc- 

 tion in living things as small as bacteria cannot be too involved, 

 and when compared with multicellular organisms, bacteria do em- 

 ploy a relatively simple reproductive process. At a given signal, 

 best comprehended by bacteria, the single cells split in half across 

 their short axis ( at right angles to the long axis ) , in a process called 

 BINARY FISSION. It is this simple equal division which gives bacteria 

 their class designation of Schizomycetes (schizo, split; mijket, 

 fungus). Strictly speaking, growth means enlargement or increase 

 in cell substance, but in bacteriology the terms "growth" and "re- 

 production" are sometimes loosely used as synonyms. 



Just prior to cell division the protoplasm appears to gather at 

 opposite ends of the organism. A cell wall puts in its appearance 

 across the middle of the cell, with or without a visible constriction, 

 and separation into two smaller cells takes place. Each offspring 

 tlius retains a part of the parent cell in this asexual tvpe of repro- 

 duction. Recent evidence, particularly by geneticists, leads us to 

 believe that sexuality in bacteria has been demonstrated. This is 

 not meant to imply that "female" and "male" bacteria exist in the 

 same form that we think of females and males in higher planes of 

 life. But it has been shown that when different strains of a given 

 species of bacteria are grown together in a test tube (in vitro), 

 selected isolations from these mixtures can be demonstrated to have 

 nutritional requirements different from those exhibited by either 

 of the two original strains. Some tvpe of conjugation has ap- 

 parently occurred, and this type of combination stronglv suggests 

 sexual reproduction in contrast to simple binary fission. 



When a bacterial cell divides, the two small offspring waste 

 little time growing to a predetermined maximum size. These two 

 new cells are then ready to divide, and under ideal conditions binary 

 fission can take place on an average of once every 20 or 30 minutes 

 for many species. Generation times longer than this are not un- 

 ccmmon, however, among some of the slower-growing bacteria. 

 Fortunately for mankind this multiph'cation of microorganisms does 



