GENERAL CHARACTERISTICS OF BACTERIA 



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The production of endospores in the different species of bacteria, 

 though not identical, is very similar. To observe the formation of 

 spores in any species it is best to employ a streak culture on nutrient 

 agar or a potato culture, which should be kept at the temperature nearest 

 the optimum of the organism to be examined. At the end of twelve, 

 eighteen, twenty-four, thirty, thirty-six hours, etc., specimen's of the 

 culture are observed first unstained in a hanging drop or agar block, 

 and then, if round or oval, highly refractile bodies are seen, they should 

 be stained for spores. A bacillus, as a rule, produces but one spore, and 

 more than two have never been observed. 



According to Fischer motile bacteria always come to a state of rest 

 or immobility previous to spore formation. Several species first become 

 elongated. The anthrax bacillus does this, and a description of the 

 method of its production of spores may serve as an illustration of the 

 process. In the beginning the protoplasm of the elongated filaments 

 is homogeneous, but after a time it becomes turbid and finely granular. 



FJG. 17 



FIG. 18 





Unstained spores in slightly distended 

 bacilli. (The spores are the light oval 

 spaces in the heavily stained bacilli.) 



Unstained spores in distended ends of 

 bacilli. 



These fine granules are then replaced by a smaller number of coarser 

 granules, which are finally amalgamated into a spherical or oval refrac- 

 tile body. This is the spore. As soon as the process is completed there 

 appears between two spores a delicate partition wall. For a time the 

 spores are retained in a linear position by the cell membrane of the 

 bacillus, but this is later dissolved or broken up and the spores are set 

 free. Not all the cells that make the effort to form spores, as shown by 

 the spherical bodies contained in them, bring these to maturity; indeed, 

 many varieties, under certain cultural conditions, lose their property of 

 forming spores. The following are the most important spore types: 

 (a) the spore lying in the interior of single, short, undistended cells; 

 /' the spores lying in the interior of a chain of undistended cells 

 Fig. 7) ; (c) the spore lying at the extremity of a cell much enlarged 

 at that end the so-called "head spore " (Fig. 18); and (d) the spore 

 lying in the interior of a cell very much enlarged in its central portion, 

 giving it a spindle shape. 



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