138 Marine Microbiology 



1,054 isolates grown in medium B. It was found that physio- 

 logically significant amounts of biotin and thiamine were pro- 

 duced by about half of the cultures, while nicotinic acid and B12 

 were synthesized in appreciable amounts by somewhat fewer 

 isolates. Vitamin production by auxotrophic cultures having cer- 

 tain specific vitamin requirements was also studied with the 

 usual procedures. Results obtained in studies of nine different 

 groups of cultures, each with its own pattern of vitamin require- 

 ments, indicated that some cultures produced no detectable 

 amounts of the four vitamins, while others formed one or more 

 of the B vitamins in about the same amounts as in cultures hav- 

 ing no special requirements (Table 4). 



TABLE 4 



Production of B Vitamins by Selected Groups of Growth-factor-requiring 

 Bacteria. Average Production of Vitamins is Indicated for the Various 

 Numbers of Cultures in Each Group by Showing the Radial Zones in 

 MM. OF Growth Promotion at the Edge of the Paper Discs Laid on Seeded 

 Agar Plates Containing Test Bacteria. — =Requirement, 0=No Re- 

 quirement. 



Number Pattern of Requirements Relative Productivity 



of Nicotinic Nicotinic 



Cultures Biotin Thiamine Acid Bis Biotin Thiamine Acid Bis 



