the cell material was filtered onto a tared millipore disc, dried, counted 



and weighed. The results of the uptake studies conducted on the heat killed 



cells are given in Table 5 and 6. While it was previously noted that living 



cells could clearly demonstrate an ability to differentiate between strontium 



and yttrium, the adsorption by heat killed cells showed no such selectivity. 



With the exception of K. rotundata the accumulation of strontium-90 by the 



organisms which had been heat killed was nearly equal to that which had been 



accumulated by the living cells during the same length of time (Table 6). 



This would seem to indicate that adsorption or ion exchange may play a role 



in the accumulation of ions. Since heat killing does bring about changes in 



the cell wall, it is difficult to determine whether the accumulation was an 



adsorptive process. 



Table 5. Accumulation of radioactive strontium and yttrium 

 by heat killed cells after 48 hours exposure. 



Species or °U Activity °L Activity 



Culture No. From Sr. From Yttrium 



G. simplex 3 97 



K. rotundata 2 98 



4000 m A. 4 96 



35 m A. 3 97 



10 m G. C. 4 96 



Table 6. Comparison of the radioactive strontium accumulated 



by living and heat killed cells after 48 hours exposure, 



Species or Living Cells Dead Cells 



Culture No. M-c/g dry weight M-c/g dry weight 



G. simplex 3.5 3.3 



K. rotundata 40.7 4.5 



4000 A 3.7 4.7 



35 A 4.3 4.3 



10 G. C. 3.7 3,8 



17- 



