The purine and pyrimidine pool had the most 

 marked stimulatory effect on the bacterial 

 multiplication in the various treatments. 

 When the purine and pyrimidine pool was re- 

 moved from the complete complement of addi- 

 tives, the bacterial increase in both the 

 light and dark bottles were little more than 

 twice the number of those in the untreated 

 controls. Increases of sixfold were recorded 

 (Table 15) when the purine and pyrimidine 

 pool was present. The bacteria did not appear 

 to be inhibited by the vitamin pools. In fact, 

 the vitamins stimulated bacterial development 

 somewhat in all cases. The inorganic addi- 

 tions failed to promote more than a twofold 

 increase in the number of bacteria. 



In the experiment reported in Table 15, C 1 ^ 

 assimilated by the phytoplankton was inhibited 

 by the vitamin pools. Since these vitamin 

 pools were prepared in 50° /o ethanol to pre- 

 serve their sterility, the possibility that 

 the alcohol per se was depressing the C^ up- 

 take by the plants was considered. The final 

 concentration of ethanol was 0.15/° • 



In the following experiment, the ethanol was 

 removed from the vitamin pools by hot-air 

 evaporation at 35°C. After the alcohol was 

 removed, the original volume of the pools 

 was reconstituted by adding distilled water. 

 A surface sea-water sample was collected in 

 the same manner as before at ll4-°27' N latitude, 

 98°58' w longitude} (Station BT - 5 - 7) • The 

 temperature of the surface sea water was 28.0°C. 

 Control bottles to which no additions were made 

 were prepared in three different ways: 1) cleans- 

 ed and rinsed with 95°/o ethanol, followed by 

 five or six rinses with the sample sea water, 

 2) cleaned with a detergent, rinsed with sea 

 water, rinsed with 10°/. HC1, rinsed five or six 

 more times with sea water and autoclaved for 

 15 minutes at 15 lbs. pressure, 3) bottles rins- 

 ed five or six times with sample 6ea water. All 

 of the bottles to which nutrients were added 

 were prepared as described in the first method 

 with 95*/o ethanol followed by five or six 

 rinsings with sample sea water. 



The same additions were made in this experi- 

 ment as in the last experiment (Table 15) ex- 

 cept that the final inorganic treatment (KNOo, 

 K/>HP0l, and Hoagland and Arnon's trace ele- 

 ments) were not repeated. These bottles were 

 incubated in the illuminated water bath for 

 four hours at 28 ± 2 C. After four hours 

 both the light and dark bottles were removed 

 and 5,222,500 counts/minute NaHC 11 ^ were 

 added. The bottles were returned to the water 

 bath for two more hours of incubation (total 

 of six hours), after which the final bacterial- 

 assay plates were poured and the contents of 

 the bottles filtered for C 1 ^ uptake. The re- 

 sults are presented in Table l6. The initial 

 bacterial numbers, which varied between 6I4O 

 and 1,250 bacteria/ml, were subtracted from 

 the final count to determine the bacterial 

 increase/ml. 



These results confirm the conclusion of the 

 previous experiment (Table 15) regarding the 

 inhibition of photosynthesis by the vitamin 

 pools . The removal of the ethanol from the 

 vitamin pools made little difference on the 

 C 1 ^02 assimilation of the phytoplankton in 

 the presence of these pools. Consequently, 

 it may be concluded that the vitamin pools 

 themselves exerted some inhibitory effect on 

 C 1 * uptake by phytoplankton in the light. 

 Where the vitamin pools were omitted and the 

 purine and pyrimidine pool as well as the in- 

 organic additions were added, photosynthesis 

 was almost doubled compared to the untreated 

 control (Table l6) . 



The dark fixation in the treated bottles was 

 1.5 to 2.0 times greater than that in the 

 untreated control. The greatest dark fixa- 

 tion was in the sample containing the purine 

 and pryimidine pool plus the inorganic addi- 

 tions as in the light. The bacterial increase 

 in this treatment was considerable, 1+1,000 

 bacteria/ml. as compared with 12,1)00 bacteria/ 

 ml. in the control dark bottles. 



The most marked bacterial increase in this ex- 

 periment was that resulting from the combined 

 treatment (vitamin pools, purine and pyrimidine 

 pool, and inorganic additions), 82,000 bac- 

 teria/ml in the light and 28,000 bacterial/ml 



92 - 



