CHARACTER OF BACTERIA 19 



northern plants, so do some bacteria require a warmer 

 or a colder environment than others. Bacteria accus- 

 tomed to grow in the body of warm-blooded animals 

 usually grow best at a temperature near 100 F. On 

 the other hand, the bacteria normally growing in water, 

 for example, usually grow best at a temperature of 

 about 60 F. Certain bacteria, growing in manure, 

 grow best at a temperature considerably above 100 F. 



Fig. 5. Streak culture of the potato bacillus (natural size), 

 showing an aerobic organism which will not grow under a cover-glass 

 (Williams). 



All bacteria require a certain amount of moisture 

 for their growth. Moreover, many bacteria die if they 

 are allowed to dry. 



The necessity for protecting bacteria which we wish 

 to cultivate against an undue amount of light, particu- 

 larly against sunlight, is understood when one recalls 



