400 KELLERMAN AND SMITH! CALCIUM CARBONATE 



BACTERIOLOGY. — Bacterial precipitation of calcium carbonate. 

 Karl F. Kellerman and N. R. Smith, Bureau of Plant 

 Industry. 



In 1914 the late George H. Drew^ called attention to the prob- 

 able importance of bacteria in the formation of marine deposits 

 of calcium carbonate. He isolated and designated as Bacterium 

 colds an organism which, cultivated in the laboratory, precipi- 

 tated calcium carbonate from synthetic cultural media. At the' 

 suggestion of Dr. T. Wayland Vaughan, in charge of Coastal 

 Plain Investigations, U. S. Geological Survey, we have under- 

 taken a bacteriological study of samples of water and oolitic sand 

 from the Great Salt Lake and from the Atlantic Ocean near the 

 Bahamas and the Florida Keys. The samples of water and 

 bottom mud which served as a basis for these experiments were 

 obtained through the courtesy of Dr. Vaughan. 



The progress of this study has been necessarily slow, since the 

 elaboration of new technique is required in dealing with such 

 unusual conditions. At the present time, however, it is believed 

 that some important fa'cts have been established. We have 

 found it possible in the laboratory to form precipitates of calcium 

 carbonate by three types of biological processes. These are 

 briefly outlined below in the probable order of their importance. 



1. The associative action of mixed cultures of bacteria, one 

 species which forms traces of carbon dioxide and one which 

 forms ammonia either by decomposing some proteid or by redu- 

 cing nitrates to nitrites and to ammonia, gives rise to ammonium 

 carbonate. This ammonium carbonate reacts with any calcium 

 sulphate which may be in solution according to the formula: 



CaS04 + (NH4)2 CO3 = CaCOs + (NH4)2S04 

 It is obvious that the carbon dioxide necessary for this reaction 

 may be produced by plant or animal catabolism as well as by 

 bacterial fermentation. 



^ Drew, George Harold. On the Precipitation of Calcium Carbonate in the 

 Sea by Marine Bacteria, and on the Action of Denitrifying Bacteria in Tropical 

 and Temperate Seas. Publ. No. 182, Carnegie Institution of Washington, p. 7- 

 45. 1914. 



