134 Marine Microbiology 



sediments obtained from tropical, temperate, and sub-arctic 

 regions. The composition of media suitable for isolation, testing, 

 and maintenance of many marine bacteria is given in Table 1. For 

 the purpose of determining special requirements for vitamins, 

 amino acids, purines, p}Timidines, etc., chemically defined media 

 were prepared by adding suitable supplements to artificial sea 

 water. In some instances vitamin-free casein hydiolysates sup- 

 plemented with cystine and tryptophane were used to satisfy 

 nitrogen needs, or when indicated, each of the desired amino 

 acids was used in the proportion present in casein. Requirements 

 were determined by testing growth of each organism in a series 

 of media having single omissions of compounds from the com- 

 plete medium. For certain studies of B vitamin relationships in 

 gel substrates, addition of 1.5 per cent Difco purified agar to the 

 liquid media proved satisfactory. 



The general growth requirements of 1748 aerobic, hetero- 

 trophic bacteria are presented in Table 2, for the purpose of in- 

 dicating tlie characteristics of populations commonly occurring 

 in marine muds. Analysis of the vitamin requirements of these 

 cultures has provided data on the statistical occurrence of vita- 

 min deficiency in this whole group of auxotrophic bacteria. The 

 data, summarized in Table 3, show that biotin and thiamine are 

 most frequently required, cobalamin and nicotinic acid stand 

 next, while pantothenate and riboflavin requirements occur in- 

 frequently. The occurrence of vitamin deficiency may be a single 

 or multiple requirement in various cultures. Some need as many 

 as four B vitamins. Upon further inspection, it is found that the 

 specificity of response to difi^erent forms of the vitamin B12 group 

 or the intermediates of thiamine, or different structures related 

 to biotin or nicotinic acid, may vary to a considerable degree 

 among the difi^erent isolates. Thus all Bi2 requiring isolates appear 

 to respond to cyanocobalamin, but some are unable to utilize 

 pseudovitamin B12, or factors A and B. Numerous thiamine-de- 

 ficient strains show ability to grow in response to either the pyr- 

 imidine or thiazole moieties; Some biotin requirers can use des- 

 thiobiotin, and so on. 



Our data, along with results of many other investigators, in- 

 dicate widespread requirement for exogenous sources of B vita- 



