330 AUTOTROPHIC BACTERIA 



Although biological oxidation of phosphorus compounds has not been investi- 

 gated, it is reasonable to believe that autotrophic processes may be concerned in such 

 transformations. 



INFLUENCE OP ORGANIC MATERIALS ON AUTOTROPHIC BACTERIA 



The influence which organic compounds exert upon autotrophic bacteria is still 

 a disputed point. These organisms fail to develop where organic materials furnish the 

 sole source of energy in the medium. Further, no organic materials replace carbon 

 dioxide as a source of carbon. However, even in the presence of the specific inorganic 

 sources of energy, organic materials may exert pronounced inhibitory effects upon the 

 development of autotrophic bacteria. 



Of the iron bacteria, L. ochracea appeared indifferent to considerable concentra- 

 tions of organic matter, but G. ferriiginea was quite sensitive to such substances as 

 peptone, sucrose, and asparagine.' For the higher sulphur bacteria moderate amounts 

 of organic materials do not appear to be injurious.^ 



Oxidation by Th. thiooxidans was not appreciably affected by even 5 per cent 

 glucose.^ Considerable citric acid (i per cent) exerted no effects on growth, but lower 

 concentrations were tolerated than of sulphuric acid. It was early noted that some 

 organic materials were toxic to nitrifying bacteria." Glucose injured growth of nitrate 

 formers at 0.045 PS'" cent and completely inhibited development at 0.27 per cent. The 

 nitrate formers were less susceptible to such injury than the nitrite formers. Cole- 

 man5 noted no injury to growth of nitrate formers at 0.02-0.05 per cent glucose, but 

 larger amounts were distinctly toxic. No nitrite formation took place at 0.2 per cent 

 glucose, and even 0,02 per cent was injurious. Toxicity is very different with different 

 compounds.* 



It has been noted with Th. thiooxidans'' as well as the nitrifying organisms'^ that, 

 although glucose alone does not support growth, it disappears if introduced into 

 cultures containing the specific inorganic energy source. 



Although under optimum conditions higher plants may utilize close to 80 per cent 

 of the energy furnished by the light,' more commonly from i to 3 per cent is used. 

 Between 5 and 10 per cent of the energy liberated in the oxidation of the inorganic 

 substances is utilized by the autotrophic bacteria to reduce carbon dioxide to organic 



' Cholodny, N. : loc. cil. 



^ Winogradsky, S.: loc. cil.; Bavendamm, W.: loc. cit. 



3 Waksman, S. A., and Starkey, R. L.: loc. cil.; Starkey, R. L.: loc. cit. 



■I Winogradsky, S., and Omeliansky W.: Centralbl.J. Baktcriol., Abt. II, s, 329-43, 377-87, 429- 

 40. 1899. 



5 Coleman, L. C: Centralbl. f. Baktcriol., Abt. II, 20, 401-20, 484-513. 190S. 



•^Meyerhof, O.: loc. cit.; see also Beijerinck, M. W.: Folia Mikrobiol. (3d year), 2, 91-113. 

 1914; Winogradsky, S.: Compt. rend. Acad. Sci., 175, 301-4. 1922; Murray, T. J.: Proc. Soc. Exper. 

 Biol. b° Med., 20, 301-3. 1923; Sach, J.: loc. cit.; Fred, E. B., and Davenport, A.: Soil Sci., 11, 389- 

 404. 1921. 



7 Starkey, R. L.: loc. cit. * Coleman, L. C: loc. cit. 



"Warburg, O.: Naturmssenschaften, g, 354-58. 1921; 13, 985-93. 1925; Ztschr. phys. Chemic, 

 106, 191-218. 1923; Warburg, O., and Negelein, E.: ibid., 102, 235-66. 1922; 108, 101-2. 1924; 

 Naturwissenschaftcn, 10, 647-53. 1922. 



