Chapter 14 



Some Nutritional Relationships 



Among Microbes of 



Sea Sediments and Waters" 



Paul R. Burkholder* 



I 



n the fluid marine environment, important growth-regulat- 

 ing substances, such as water-soluble vitamins and various anti- 

 biotic substances, are synthesized, excreted, and used in diverse 

 ways by the natural populations of algae and bacteria. The pres- 

 ent discussion is concerned chiefly with certain coactions among 

 small autotrophic and heterotrophic plants that live in the sedi- 

 ments and waters of shallow seas. 



It is now recognized that auxotrophy, the requirement for 

 exogenous supplies of special metabolites in veiy small amounts, 

 predominates in algal groups with well-developed tendencies 

 toward saprophytic and holozoic modes of nutrition, and is less 

 frequently distributed in groups with strong vegetal tenden- 

 cies (8). Diatom blooms of northern seas (4) and inhabitants 

 of marine muds (5) commonly require such B vitamins as thia- 

 mine, biotin, and cobalamines. Recent studies in our labora- 

 tories (12) have shown that among marine littoral Cyanophyta 

 more than 50 per cent of isolates growing in pure culture exhibit 

 requirements for cobalamins. The auxotrophic habit appears to 

 be widely distributed among the different phyla of autotrophic 

 and heterotrophic microorganisms (10, 7, 6) that live on land 

 as well as in the waters of the earth. 



In order to appraise the significance of B vitamin auxo- 

 trophy in marine bacteria, we ha\'c isolated, in dilution pour 

 plates of rich media, more than 6,000 cultures from waters and 



*This work was supported through contract Nonr-3018 (00) between the Brook- 

 lyn Botanic Garden and the Office of Naval Research, and a grant No. G 8917 

 made to the Garden by the National Science Foundation. 



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