TABLE 1 



RESPONSE OF MUTANTS TO VARYING CONCENTRATIONS OF THEIR SPECIFIC NUTRILITES 



Growth 



Requirements 



of Mutant 



Purine* 



Biotin 



Uracil 



Concentration 



for Optimum 



Growth 



Growth Limiting 



Concentration 



Range 



Lower Limit 

 Detectable 



10 - 2.5 

 5 - 1.0 

 5 - 1.0 



.7 - -05 

 .0l+- .002 

 1.0 - .08 



.05 

 .002 



.08 



Concentrations expressed in ug/ml. 



» Purine response was measured using hypoxanthine as growth factor. The 



mutant responds to all four purine bases. 



quirements, and their optimal and limiting sub- 

 strate levels established by the optical den- 

 sity method of recording growth response. For 

 use in testing sea-water samples, these are 

 first filtered through Whatman No. 2 paper to 

 remove any large particles and then autoclaved. 

 The water samples are next divided into a num- 

 ber of replicate samples containing glycerol 

 as added carbon source, and are then inoculat- 

 ed with the mutants. Positive tests may be 

 measured in the Beckman model DU spectrophoto- 

 meter for quantitative estimation of nutrient 

 concentration, following a suitable period of 

 incubation. Each test of unknown sea water is 

 accompanied by reversion tests on the mutants, 

 as well as viability controls. 



Attempts are in progress to standardize the 

 technique of testing sea-water samples so that 

 any technician, either biologist or nonbiolo- 

 gist, may use it at sea. This would permit 

 efficient utilization of shipboard facilities 

 in that a technician in chemistry, for example, 

 could carry out these tests along with the 

 chemical work, and leave space for some other 

 member of the scientific team, by making it 

 unnecessary for a biological technician to go 

 along for this purpose. 



EXPERIMENTAL RESULTS 



The results of the tests on sea-water samples 

 are presented in Table 2 along with other SCOPE 

 data to show correlations. 



In view of the scant nature of these data and 

 the small number of samples examined, it would 

 be presumptuous to attempt to draw any conclu- 

 sions from this test. The major purpose of the 

 test was to assess the validity of the bioassay 

 system, and it seems to indicate that the syste 

 has merit. There is an indication that 

 soluble organic materials are present and are 

 distributed both laterally and vertically in 

 discontinuous fashion. In comparing the bac- 

 terial counts and the chlorophyll concentra- 

 tion with the occurrence of organic material, 

 it was encouraging to note that presence of 

 bacteria seems to be inversely correlated, 

 while there is direct correlation between algal 

 production and growth factor occurrence. 

 Whether the algae are present because growth 

 factors are present, or vice versa, and 

 whether high bacterial numbers occur at the 

 expense of external growth factors are problems 

 which will have to await further experimenta- 

 tion. A considerable amount of data would 



56 



