Marine Bacteriology and the Problem of Mineralization 49 



biological agents of soil processes, such as they are given in 

 nature, in their original soil and under the special conditions of 

 that soil. The former is free to use in his experiments all means 

 suggested by certain standard programs or by his own ideas; but 

 tlie latter has to pursue his investigations, as exactly as possible, 

 in the boundaries placed by nature itself." 



Winogradsky's statement, properly paraphrased, also gives, 

 I believe, an accurate appraisal of the current situation with 

 respect to marine bacteriology. Understanding of mineralization 

 in the marine environment illustrates his thesis, and the title of 

 this paper might well have been reversed to read "Minerahzation, 

 and tlie Problem of Marine Bacteriology." 



Minerahzation in the sense of the symposium just completed 

 is defined as the metabolic conversion of organic molecules to 

 the inorganic forms utilized as plant nutrients, and it is tlius con- 

 cerned with the completion of the nutrient cycles. Although the 

 concept of the cycling of nutrients in nature can be traced back 

 at least to the time of Lavoisier, it was the genius of Pasteur who 

 first clearly conceived the full significance of microorganisms in 

 the mineralization process. Generalizing from the results of his 

 studies on fermentation, Pasteur (15) was able to express the 

 full import of microbial activity in one brief, elegant sentence. 

 "Sans eux, la vie deviendrait impossible, parce que I'oeuvre de la 

 mort serait incomplete." 



The realization that soil fertility and microbial activity were 

 intimately connected soon led to a study of the microorganisms 

 of tlie soil. Quantitative laboratory investigations of tlie mineral- 

 ization of complex organic matter commenced witli the work 

 of von WoUny (30) and Laurent (14). However, it was the efforts 

 of Winogradsky and of Beijernick and their development of the 

 selective or enrichment culture technique, starting in the mid 

 1880's, that paved the way to the discoveiy and description of 

 the various bacteria involved in the more specialized steps of 

 mineralization. In particular, the isolation of the nitrifying organ- 

 isms (28) was a major milestone not only because it identified 

 the agents required for the completion of the nitrogen cycle but 

 also because it showed the marked specificity of function to be 

 found in the microbial world. 



