NUTRITION OF THE AUTOTROPHIC BACTERIA 



The energy and hydrogen yielding reactions are : — 

 2C2H5OH ^ 



2CH3CHO + 2H3PO4 ^=^ 2CH3C- 0- PO3H, + 4H 

 O 



// 

 2CH3C- O-PO3H2 + 2 donor ^=^ 2CH3COOH + 2 phosphate— : loner 



Organic compounds are not only not used by the strict 

 autotrophs but have a definite inhibitory effect on their 

 grov>i:,h, under artificial conditions at least. Thus it was 

 not until Winogradsky grew the nitrifying organisms on 

 media containing no carbon source other than carbon 

 dioxide that he was able to obtain cultures of them. 

 For solid media he employed silica gel in order to avoid 

 organic substances. The sulphur bacteria and some of 

 the iron bacteria are less sensitive to organic matter and 

 can grow if only low concentrations of carbon compounds 

 are present, especially if large inocula are used. The iron 

 bacterium, Leptothrix ochracea, however, is susceptible 

 to peptone, sucrose and asparagine. 



The thermodynamic efficiency of the autotrophs is 

 not very high, only about 5 to 10 per cent, of the energy 

 liberated by the oxidation of the inorganic substrate 

 being utilised in the reduction of carbon dioxide to the 

 organic compounds used for synthesis. 



For further reading : — 



H. J. Bunker, " A Review of the Physiology and Biochemistry of the 

 Sulphur Bacteria," D.S.T.R. Chemistry Research, Special Report 

 No. 3. H.M. Stationery Office. London, 1936. 



B, C. J. G. Knight, " Bacterial Nutrition," Sections B. and C. ^Medical 



Research Council Special Report No. 210. H.M. Stationery Office. 



London, 1936. 

 S. Ruben, " Photosynthesis and Phosphorylation." J. Amer. Chem. Soc. 



65, (1943) 279. 

 M. Stephenson, " Bacterial ]\Ietabolism," Chapters IX and X. Longmans, 



Green & Co. London, 2nd Edition, 1939. 



C. B. van Niel, " The Bacterial Photosyntheses and their Importance for 



the General Problem of Photosynthesis." Advances in Enzymology, 

 1 (1941), 263. 

 C. B. van Niel, " Biochemical Problems of the Chemo -.Autotrophic Bacteria." 

 Physiol. Reviews, 23 (1943), 338. 



