32 GERLOFF, FITZGERALD, AND SKOOG 



teria-free culture of Nosioc, was used to kill the bacteria associ- 

 ated with the algae. 



A dilute algal suspension was placed in a quartz-windowed 

 chamber and irradiated for 20 to 30 minutes with 2750 Angstrom 

 ultraviolet light from a quartz-jacketed mercury vapor lamp. 

 The suspension was agitated by continuous stirring during the 

 irradiation period. Samples were taken at five-minute intervals, 

 and a large number of dilution cultures was prepared from each. 

 Subcultures usually failed to grow when taken from samples 

 with long exposures and were usually contaminated when taken 

 from samples with short exposures. Certain subcultures, however, 

 particularly from samples with intermediate exposures, were 

 found to be free of bacteria. Obviously, not all the bacteria were 

 killed in the irradiation chamber, nor did all the algae survive. 

 Rather, the algae were slightly more resistant to the ultra-violet 

 than the bacteria, so that by sufficient dilution of some samples it 

 was possible to isolate a few cells or algal filaments free of bac- 

 teria. 



After preliminary tests in a yeast-dextrose medium had indi- 

 cated that the algae were free of bacteria, they were further 

 checked for purity on sodium caseinate agar to detect aerobic 

 bacteria (other than nitrogen-fixers) and Actinomycetes (Stark 

 and McCoy, 1938), in both Ashby's and Burk's nitrogen-free 

 media for Azobacter (Wilson and Knight, 1947), and in Brew- 

 er's medium for anaerobes (Brewer, 1940). 



Nine of the species in Table i have been freed of bacteria by 

 the above procedure, and a tenth pure culture has not been iden- 

 tified as yet. Although these cultures include a variety of growth 

 forms, the majority were purified by one or two treatments with 

 ultra-violet light. The method, therefore, is relatively simple and 

 should be satisfactory for purification of the remaining species. 



Mineral Nutrition of Coccochloris Peniocystis 



Experimental Procedure 



Because Coccochloris Peniocystis (Kiitz.) Drouet and Daily 

 [Gloeotkece linearis Nag.] was the first rapid-growing, identified 



