Some Nutritional Relationships Among Microbes 149 



sea waters and sediments, requirements for biotin, thiamine, 

 cobalamine, and nicotinic acid occur commonly, while needs 

 for exogenous pantothenate, riboflavin, and otlier vitamins are 

 found infrequently. 



2. Production of various B vitamins is demonstrable in 

 cultures of many algae and bacteria isolated from the sea. Certain 

 vitamins are excreted along with other metabolites during growth 

 of some algae and bacteria while others, such as Bi and B12, are 

 often more tightly bound within the cells. While the presence 

 of such \'itamin substances is readily observed in crude collec- 

 tions of phytoplankton and marine macrophytes, one may not 

 easily conclude that all of these substances are synthesized in 

 organisms where they are found in nature. 



3. The direct availability of vitamins and other metabolites 

 formed by primary producers in the sea may often be regulated 

 by selective inhibitory action of "antibiotic" substances produced 

 by plankton on a vast scale or by various algae and bacteria in 

 more localized habitats. 



4. Products of organisms commonly are utilized in sequence 

 by others, in accordance with the general principles of metabiosis, 

 and it has been demonstrated, also, that simultaneous exchanges 

 of metabolites can occur among living microorganisms in marine 

 communities. Our observations indicate that complex relation- 

 ships in mixed populations often involve delicate adjustments 

 of syntrophism, antibiosis, and other types of coactions. 



REFERENCES 



1. Barton-Wright, E.: Microbiological assay of the xitamin B-complex 



and amino acids. Pitman Pub. Corp., New York, 1952, 179 p. 



2. BuRKHOLDER, P. R., and Burkholder, L. M.: Studies on B vitamins in 



relation to productivity of the Bahia Fosforescente, Puerto Rico. 

 Bull. Mar. Sci. Gulf and Carib., 8:201-223, 1958. 



3. Burkholder, P. R., Burkholder, L. M., and Almodovar, L.: Antibio- 



tic activity of some marine algae of Puerto Rico. Bot. Mar., 2:149- 

 156, 1960. 



4. Droop, M. R.: A pelagic marine diatom requiring cobalamin. /. Mar. 



Biol Assoc. U. K., .34:229-231, 1955. 



5. Lewin, J., and Lewin, R. A.: Auxotrophy and lieterotrophy in marine 



littoral diatoms. Int. Oceanogra. Cong. Preprints, p. 928-929, 1959. 



6. LocKHEAD, A. C, and Burton, M. O.: Qualitative studies of soil micro- 



