50 Marine Microbiology 



In the succeeding two decades, a large number of meta- 

 bolically specialized bacteria of potential significance in mineral- 

 ization were uncovered, as for example the nitrogen fixers, vari- 

 ous sulfur oxidizers, cellulose and agar digesters and so on. By 

 the early 1900's, schematic nutrient cycles, of varying degrees 

 of complexity for the individual key elements were included in 

 standard textbooks. The physiologically unique microorganisms 

 described during this period proved to have a fascination for 

 succeeding generations of microbiologists who have continued 

 to study them as interesting entities in themselves without neces- 

 sarily relating their investigations to the problems of the soil. 



Marine bacteriology had its beginnings in the same era. 

 Concomitantly with the study of the soil microorganisms, a lesser 

 effort was expended in the description of the marine microflora. 

 Using techniques aheady applied to the soil, Certes (4), Fischer 

 (9), Russel (21) and other pioneers demonstrated the existence 

 of a general heterotrophic flora, very similar to the heterotrophic 

 bacteria of the soil, in sea water and in marine sediments. 



By applying specific enrichment culture procedures, also 

 borrowed from soil studies, the activities of physiologically spe- 

 cialized forms was also demonstrated. Nitrification, denitrification, 

 nitrogen fixation, agar and chitin digestion, sulfide oxidation and 

 sulfate reduction, among other processes were shown to occur 

 in the enrichment cultures. In many investigations, it was tacitly 

 assumed that the bacteria involved were the marine counterparts 

 of the previously described soil forms and the experimenters 

 were content to demonstrate only the chemical change. A careful 

 reading of the literature leaves the impression that the agents 

 responsible for many of the important transfomiations in the 

 oceans, including nitrification, are yet to be described and sug- 

 gests that even the descriptive phase of marine bacteriology is 

 far from complete. 



Not only were individual mineralization steps demonstrated 

 in the laboratory, but also, if only in rough form, complete cycles. 

 The classical paper of von Brand, Rakestraw and Renn (1), 

 showing the successive formation of ammonia, nitrite and nitrate 

 from decomposing plankton, is a most elegant example. Since 

 the chemical oceanographers had demonstrated the same se- 



