A preliminary study in which G. simplex and K. rotundata were used as 

 test organisi^is showed that K. rotundata failed to accumulate the isotope and 

 the uptake by G. simplex was extremely small. The G. simplex cells from those 

 preliminary tests were centrifuged and washed three times with sterile sea water 

 and resuspended in fresh medium to determine loss of the iostope. 



K. rotundata was not used again for Cs-Ba uptake studies. Further studies 

 were conducted with G. simplex . Eight 125-ml flasks containing 52.5 mis of 

 culture medium were inoculated with G. s imp lex and incubated four (4) days or 

 until they were well into their logarithmic growth phase. At that time five 

 milliliters of Cs-Ba-'--^^ solution was added to each flask giving an activity 

 of approximately 25,000 cpm./ml to the medium. 



The accumulation of Cesium-barium- 137 by G. simplex was determined by 

 removing 10 ml aliquot samples after various exposure periods. The cells from 

 the 10-ml sample aliquots were centrifuged out of suspension, washed with sterile 

 sea water, re-centrifuged and resuspended, then filtered onto tared HA type 

 Millipore filter pads, washed with 10 ml distilled water, dried, weighed and 

 counted. Both scintillation and gas-flow counters were utilized. Triplicate 

 samples and duplicate flasks were used for each exposure period. The exposure 

 periods were 24, 48, 72 and 96 hours. 



The concentration factor was calculated from the result obtained from 



the 48-hour period to allow a comparison with all the prior studies. The 



following formula was used to calculate concentration factor. 



Cone, factor = c. p.m. /gram cells 

 c.p.m./ ml medium 



The loss of Cs-Ba- 137, by cells of G. simplex and N. seriata grown in 



medium containing Cs-Ba for 72 hours was determined when aliquots of cell 



suspension were placed in 15-ml centrifuge tubes and centrifuged at 1500 rpm. 



-9- 



