l6 THE METABOLISM OF ALGAE 



B Chemotrophy: energy provided entirely by dark 

 chemical reactions. 



(i) Che?nolithotrophy: growth dependent upon oxi- 

 dation of exogenous inorganic substances (e.g. 

 the 'chemosynthetic' bacterium Nitrosomonas, 

 which oxidizes ammonia to nitrite-^'^' ^^'). 



(2) Chemo-organotrophy: growth dependent upon 

 oxidation or fermentation of exogenous 

 organic substances (e.g. non-photosynthetic 

 bacteria, fungi and animals). 



II. Nomenclature based upon ability to synthesize essential 

 metabolites. 



A Autotrophy: all essential metabolites are synthesized 

 (e.g. most green plants), 

 (i) Autotrophy seiisu stricto: ability to reduce 



oxidized inorganic nutrients such as nitrate. 

 (2) Mesotrophy: inability to reduce one or more 

 oxidized inorganic nutrients (=need for one 

 or more reduced inorganic nutrients such as 

 ammonia). 

 B Heterotrophy: not all essential metabolites are 

 synthesized ('=need for exogenous supply of 

 one or more essential metabolites, i.e. growth 

 factors or vitamins; animals and many fungi 

 and bacteria are of this type). 



Composite names may be used for the concise, if un- 

 couth, characterization of a nutritional type with respect 

 to the chief energy source as well as to the capacity for 

 synthesis of essential cell constituents, e.g. Chlorella vulgaris 

 is photolithoautotrophic, whereas Prototheca zopfii is 

 chemo-organoheterotrophic. To avoid confusion it should 

 be particularly noted that the terms autotrophic and hetero- 

 trophic as used in this book are as re-defined in this 

 classification. 



