ZoBell — 102 — Marine Microbiology 



which has not been enriched with either calcium salts, organic matter, or 

 nitrate. He regarded ammonia production from organic matter to be the 

 most important factor. The utilization of CO2 by plants, thereby increas- 

 ing the pJrl of sea water, was also recognized as an important factor. In a 

 later publication, Lipman (1929) averred that under ordinary conditions 

 bacteria do not possess the ability to precipitate CaCOs from sea water, a 

 conclusion which was predicated primarily upon the paucity of bacteria in 

 the open sea. This conclusion has been rendered untenable by the large 

 numbers of bacteria found in marine bottom deposits, particularly cal- 

 careous deposits (Bavendamm, 1932). 



Being guided by the work of Drew, who regarded CaCOs precipitation 

 as being due to specific "calcium bacteria," Molisch (1925) reported the 

 discovery of aquatic bacteria which precipitate CaCOs by the formation of 

 ammonia. He isolated Pseudomonas calcipraecipitans from sea water 

 and Pseudomonas calciphilia from fresh water. Molisch also described 

 an Actinomyces sp. and a pink yeast, Saccharomyces olexudans, both of 

 which allegedly precipitate CaCOs. 



Smith (1926) grouped bacteria from "chalky mud" from the Bahama 

 Banks into six categories according to their physiological activities and 

 morphology. Only two groups, denitrifiers of the Pseudomonas calcis type 

 and strong ammoniiiers, formed calcite from calcium sulfate in sea water. 

 Sterilized bottom mud was employed as a source of nutrients. The addi- 

 tion of peptone and nitrate increased calcite formation. The production 

 of calcite aggregations was enhanced by the presence of 0.2 per cent agar. 



From a review of the rather extensive literature on the subject and his 

 own investigations, Bavendamm (1931, 1932) concluded that calcium pre- 

 cipitation in tropical seas is primarily a microbiological process but that 

 there are no specific "calcium bacteria." He correctly emphasized that 

 microbiological precipitation can be ascribed only to certain marine sec- 

 tions. In other regions of the ocean, microorganisms may be dissolving 

 calcareous deposits. Soil bacteria studied by Murray and Love (1929) 

 produced enough acids, including carbonic acid, from organic matter to 

 make them much more effective than atmospheric carbon dioxide in dis- 

 solving limestone. 



Whether the combined activities of microorganisms will tend to pre- 

 cipitate or dissolve CaCOs depends upon the sum total of their effects on 

 chemical and physico-chemical conditions, their effect on the />H of the 

 environment being one of the most important considerations. While auto- 

 trophic organisms are instrumental in the process, microbiological CaCOs 

 precipitation is confined largely to sections where there is an abundance 

 of organic matter. This condition is not fuliilled over most of the sea bot- 

 tom, but it is certainly met in shallow, swampy areas where there is 

 much CaCOs deposition. 



Although their preliminary experiments failed to prove the connection 

 of the activity of microorganisms and the precipitation of CaCOs within 

 the deposits of Lake Mendota, Williams and McCoy (1934) isolated from 

 the lake deposits many aerobic organisms which were capable of precipitat- 

 ing CaCOs under artificial conditions. They also examined several com- 

 monly known bacterial species which were endowed with this ability. 

 Some of the bacteria precipitated CaCOs from solutions carrying the same 

 amount of calcium as does lake water. Believing that nitrate reduction, 

 the oxidation of organic calcium salts, or ammonia production from nitro- 

 genous material accounted for the microbiological precipitation of CaCOs, 



