CARBON DIOXIDE EEQUIREMENT 107 



CI. acetobutylicum from molasses, are highly exacting as a 

 result of constant growth in these complex but inanimate 

 media. 



Table X outlines the growth requirements of various 

 selected species that are mentioned in this book. 



Carbon dioxide requirement 



A distinction has been drawn between the autotrophic and 

 heterotrophic bacteria partly on the grounds that the former 

 utilise carbon dioxide as sole source of carbon, while the latter 

 utilise organic material as carbon source. It is not true, 

 however, that the heterotrophic bacteria are unable to utilise 

 carbon dioxide, for carbon dioxide is actually essential for the 

 growth of many, if not all, heterotrophic species. Whereas 

 the autotrophes utilise carbon dioxide as sole source of carbon, 

 the heterotrophes require traces only as a source of certain 

 essential carbon compounds. The requirement of carbon 

 dioxide was demonstrated by Gladstone and others, who 

 showed that if simple media are rendered COg-free, then many 

 heterotrophic organisms cannot grow or their growth is 

 greatly delayed, e.g. neither Esch. coli nor Eberthella typhosa 

 will grow in the absence of carbon dioxide, while the growth 

 of Staph, aureus is greatly delayed, presumably until the 

 metabolic activities of the inoculum have produced a threshold 

 concentration. The full function of carbon dioxide has not 

 yet been elucidated, but it has been shown in the case of the 

 fermentation of many organisms such as Esch. coli, the 

 Propionibacteria, etc., that carbon dioxide assimilation is 

 involved in the formation of succinic and other 4-carbon 

 dicarboxylic acids (see Chap. YII). 



KNOWLEDGE OF SYNTHETIC PROCESSES FROM GROWTH 

 REQUIREMENTS 



By studying the growth of bacteria in mixtures of pure 

 chemicals, we are able to divide organisms up into nutritional 

 groups along the lines indicated above. We start, on the one 



