154 GENERAL MICROBIOLOGY 



Metatrophic, requiring organic food (e.g., zymogenic 



bacteria, saprophytes and facultative parasites) ; 

 Paratrophic, requiring living food (e.g., obligate para- 

 sites); (A. Fischer). 



According to special food preferred, into: 

 Acidophile: acid loving; 

 Halophile: salt loving; 

 Saccharophile: sugar loving; 

 Saprophile: loving dead organic matter; 

 Coprophile: loving barnyard manure. 

 According to their oxygen requirements, into : 



Aerobic: requiring atmospheric oxygen for growth; 

 Anaerobic: requiring the absence of atmospheric oxygen; 

 Partial anaerobic: requiring an intermediate oxygen 



tolerance. 



According to the necessity of one kind of food or environ- 

 ment, into: 

 Obligate: indicating absolute requirements, e.g., obligate 



parasite, obligate anaerobe; 



Facultative: indicating a variability in requirements; 

 the word following indicates the condition under 

 which the organism may live but does not prefer for 

 growth, e.g., B. coli is a facultative anaerobe. 

 According to their metabolic products, into : 

 Chromogenic, or pigment-producing bacteria; 

 Photogenic, or light-producing bacteria; 

 Aerogenic, or gas-producing bacteria; 

 Thermogenic, or heat-producing bacteria. 

 Chromogenic bacteria are classified in accordance with 

 the nature and location of the coloring matter which they 

 elaborate, as 



Chromophorus bacteria, the pigment being stored in the 

 cell protoplasm of the organism analogous to the chlorophyll 

 of higher plants, e.g., green bacteria and red sulphur bac- 

 teria, purple bacteria. 



Chromoparous bacteria, true pigment formers. The pig- 



