Chapter VII — 103 — Activities in Deposits 



Williams and McCoy employed media which contained either peptone, 

 calcium lactate, or potassium nitrate besides various other ingredients. 



Kalantarian and Petkossian (1932) isolated Bacterium sewanense 

 from Lake Sewan, Transcaucasia, Russia. This organism was believed to 

 induce the precipitation of CaCOs by reducing nitrate and producing 

 ammonia. 



From his extensive review of the literature, Baier (1937a) lists the fol- 

 lowing ways in which microorganisms may influence CaCOg equilibrium: 

 (a) by their effect on the p\l, {b) by producing or consuming CO2, (c) by 

 oxidizing organic calcium salts and (d) by assimilating calcium. The di- 

 rection and extent of the reactions depends upon the types of microorgan- 

 isms present, the chemical composition of their surroundings, and other 

 environmental conditions. 



■ Deposition of iron and manganese : — There are several ways in 

 which microorganisms are instrumental in the deposition and transforma- 

 tion of iron and manganese. Autotrophic species such as Lepiothrix 

 ochracea and Gallionella ferruginea, which allegedly obtain their energy 

 requirements by oxidizing ferrous iron, are generally associated with iron- 

 bearing waters and bog-iron deposits. Similarly, species of Siderocapsa, 

 Crenothrix, Cladothrix, and Clonothrix are often found in iron-bearing sur- 

 face waters as revealed by the literature reviewed by Hakder (191 9), 

 Ellis (1919), Cholodny (1926), Dorff (1935), and Baier (1937&). The 

 taxonomic position and metabolism of many of the so-called "iron- 

 bacteria" are highly problematical but such organisms do promote the 

 deposition of iron either directly or indirectly. 



Harder (1919) reports that, "iron-depositing thread-bacteria have 

 never been found in sea water and probably do not occur there on account 

 of the high percentage of certain inorganic salts." However, Cholodny 

 (1926) has shown that iron bacteria can develop in chalybeate waters, the 

 salt content of which is greater than that of sea water. Thiel (1925) re- 

 ports finding in marine mud numerous heterotrophic bacteria and molds 

 which precipitate iron and manganese, but he names no species. 



BuTKEViCH (1928) isolated Gallionella turtuosa from the Petschora Sea 

 and Gallionella retiadosa from the White Sea. The organisms were found 

 in ferromanganese concretions in bottom deposits. Lepiothrix longissima 

 was isolated from the sea by Molisch (1910). 



In the black mud of the Sea of Azov and the Black Sea, Issatchenko 

 (191 2) found Spirillum levocolelaenum, an organism which precipitates 

 iron sulfide in the bacterial cell. Issatchenko (1929) believed that bac- 

 teria are the chief agents in the formation of pyrite. While ferrous sulfide 

 is formed intracellularly by some bacteria and deposited as pyrite follow- 

 ing their death, any bacteria which produce HoS may contribute to the 

 deposition of iron as pyrite. 



Besides the autotrophic bacteria which oxidize iron or manganese to 

 the corresponding hydroxides and the heterotrophs which precipitate the 

 metals as sulfides by producing H2S, there are other ways in which micro- 

 biological activities contribute to the deposition or transformation of iron. 

 Starkey and Halvorson (1927) believe that heterotrophic organisms 

 play a more important role in the deposition of iron than do autotrophs. 

 This the heterotrophs do by decomposing organic compounds of iron, by 

 changing the pH of the water or mud, and by altering the oxygen tension 

 or Eh. Both the Eh and pH of a system influence the state of iron. By 



