GEOLOGY OF CENTRAL MINAS GEILiES, BRAZIL 401 



as a whole possesses certain general physiological characteristics. 

 They all live in clear water, either standing or running water. 

 Lieske states that he has never found any in turbid water, nor in 

 waters containing a great deal of organic matter."^ They live in 

 waters containing iron compounds in solution which it is claimed by 

 Winogradsky they utilize according to the following reaction: 

 2FeC03+0+3H20=2Fe(OH)3+2CO.. Heat is liberated by this 

 reaction, and this energy together with the carbon dioxide devel- 

 oped is utilized by the bacteria to sustain life.^ Ferric hydroxide is 

 left behind and may accumulate. Other investigators, like Mo- 

 lisch,^ claim that ferrous compounds are not necessary for the phy- 

 siological processes of these organisms and that organic compounds 

 other than carbon dioxide must be present for their use. Nearly 

 all agree, however, that their activity results in the accumulation of 

 deposits of ferric hydroxide in many places. As the result of this 

 activity the water pipes of cities where the water contains a con- 

 siderable amount of ferrous carbonate have sometimes been com- 

 pletely closed.'* That certain limonite deposits have been produced 

 in this way is evidenced by the fact that in them large numbers 

 of the sheaths of these bacteria have been found.^ To quote from 

 Laf ar : 



The decomposing power of these organisms is very great, the amount of 

 ferrous oxide oxidized by their cells being a high multiple of their own weight. 

 This high chemical energy on the one hand, and the inexacting demands in the 

 shape of food on the other, secure to these bacteria an important part in the 

 economy of nature, the enormous deposits of ferruginous ocher and bog iron 

 ore, and probably certain manganese ores as well, being the result of the 

 activity of the iron bacteria.^ 



'Rudolf Lieske, "Beitrage zur Kenntnis der Physiologic von Spirophyllum 

 ferrugineum (Ellis), einem typischen Eisenbakterium," Jahrb. fiir wissenschaftliche 

 Botanik, XLIX (1911), 91-127. 



= S. Winogradsky, "Uber Eisenbakterien," Botan. Zeitung, Bd. 46 (1888), p. 261. 



3 Hans Molisch, op. cit., p. 44. 



■• F. Lafar, Technical Mycology, I (1898), 361; also I (1910), 272. 



5 A. Fischer, The Structure and Functions of Bacteria, p. 69, tr. by A. Coppen 

 Jones, Clarendon Press, Oxford, 1900. 



* F. Lafar, cited by Van Hise and Leith, op. cit., Moji. 52, U.S. Geol. Surv. (1911) 

 P- 519- 



