FIRST HETEROTROPHS AND ANAEROBES 41I 



was shown for T. thiooxidans in particular by the experi- 

 ments of K. G. Vogler, W. W. Umbreit and other authors 

 ^vho have collaborated with them/^ According to Umbreit, 

 when sulphur is oxidised by this organism there occurs a 

 phosphorylation analogous to that which takes place during 

 the oxidation of organic compounds by heterotrophs. During 

 this process the energy derived from the oxidation is fixed in 

 high-energy organic compounds of phosphorus, such as ATP, 

 so that it can be used later ^vhen cOo is assimilated under 

 anaerobic conditions. Doubt has been cast on these conclu- 

 sions by a number of authors (K. Baalsrud and K. S. 

 Baalsrud,^® R. W. Newburgh*'^ and others). However, 

 Umbreit completely confirmed his ideas by further experi- 

 ments using more refined isotopic methods.** Studies of the 

 phosphorus compounds which accumulate in the cells of 

 T. thiooxidans during the oxidation of sulphur, carried out 

 by G. A. LePage and W. W. Umbreit"^ and later by H. A. 

 Barker and A. Kornberg,^" revealed the presence of labile 

 polyphosphates, ATP and such typical metabolites of glyco- 

 lysis as phosphohexoses and phosphotrioses. During a period 

 of intensive oxidation of sulphur and assimilation of cOo T. 

 thiooxidans synthesises a store of polysaccharides ; the endo- 

 genous destruction of this is carried out by means of a glyco- 

 lytic mechanism which is present in these bacteria. 



Thus, even in regard to such typical ' strict chemoauto- 

 trophs ' as T. thiooxidans, the position is analogous to that 

 which we have discussed above in regard to green plants. 

 The metabolism of both groups of organisms is based on 

 the heterotrophic utilisation of organic materials while the 

 autotrophic mechanisms which are superimposed on this 

 basis enable the organism which possesses them to exist under 

 a greater diversity of external conditions. ^^ 



Umbreit's results have also been confirmed by work with 

 other chemoautotrophs. For example, it has been shown that 

 in hydrogen bacteria there is an accumulation of organic 

 phosphorus (mainly in the form of ATP) when hydrogen is 

 oxidised in the absence of CO2, while the amount of such 

 compounds present decreases rapidly during the process of 

 assimilation of CO2. Analogous results have been obtained 



