80 



LIFE: ITS NATURE AND ORIGIN 



a 



^ik 

 ^p^ 



v 



y 



/ 



Figure 6. Election micrograph of E. coli in the presence of bacteriophage parti- 

 cles. (Courtesy RCA Laboratories, Princeton, N. J.) 



and chlorophyll-containing plants are the purple bacteria, which re- 

 quire both hydrogen sulfide and light for their development. 1 Robert 

 L. Starkey classes known autotrophic bacteria as follows: 



A. Bacteria which oxidize compounds of nitrogen 



(a) ammonia to nitrate (Nitrosomonas, Nitrosococcus) 



(b) nitrite to nitrate (Nitrobacter) 



B. Bacteria which oxidize sulfur and compounds of sulfur 

 (a) Simple bacteria (genus Thiobacillus) 



(1) Strictly autotrophic 

 a) Aerobic 



