110 Marine Microbiology 



growth is substantially similar to the one of Bij (Table 2). On the 

 contrary, some analogs are more active than Bu, for other 

 auxotrophs, i.e., pseiido vitamin B12 for Euglena gracilis (3), and 

 Factor III for Goniotrichun elegans (5). Aside from the minute 

 heterotrophy represented by the need for growth factors, all the 

 species tested are good photoautotrophs. Nitrate is an excellent 

 N source (optimal range 5-30 mg%). Ammonium sulfate is toxic 

 for G. californicum at 0.5 mg%, for E. cassithica, P. chattoni, and 

 F. baUicum at 1 mg%, and for A. carted and A. rhynchocephalum 

 at 10 mg% (lowest concentrations tried). Unfortunately these 

 concentrations far exceed those in seawater. Quite likely at very 

 low concentiations, ammonia is a good N source even in the 

 alkaline range; ammonia in the neutral or acid range is non-toxic 

 and utilized by most — probably all — algae. 



TABLE 2 



Growth Response to Different Bi: Analogues (Cells per ml.) 

 Amphidinium A. rhyncho- Gyrodinium G. G. 



B12 Analogues carteri cephalum californicum uncatenum resplendens 



(1) Forty days growth in ASPi (with biotin and thiamine added), no carbon 

 sources. 



(2) Two months growth in ASP2 (without vitamins) enriched with 10 mg% 

 each of glycine, asparagine, arginine and glutamic acid. 



It is of ecological interest to know whether even photoauto- 

 trophs have heterotrophic abilities. The dissolved organic matter 



