660 



Marine Microbiology 



ments with tlie beach flea, Gammarus, were set up with and 

 without pretreatment by terramycin. The results, as seen in Fig- 

 ure 4, show that lack of bacteria inhibits radiophosphorus ab- 

 sorption. Evidently direct absorption of inorganic P does not oc- 

 cur appreciably either through the body wall, intestine or gills. 

 This result is in general agreement with various recorded experi- 

 ments which show that higher invertebrates obtain tlieir food by 



100 



Z O 



O C 

 O UJ 



I- 

 < 



< 



UJ 



120 



100 



80 



60 



cn 



cr 



< 



< 



o 5 



P I- 



*^ z 



a: _ 40 



20 



I I I M 1 1 1 1 I I I I I M 



HOURS (LOG SCALE) .* 



CONTROL 



Fig. 4. Uptake of P^- by marine Gammarus after antibiotic treatment. 

 Specimens were washed in sterile sea water, then treated for one hour on 

 each of two successive days with terramycin in a concentration of 100 mg 

 per 100 ml water. After treatment, the animals were transferred to flasks 

 of sterile sea water for the experiment. Checks were made for bacterial 

 growth in each flask as animals were removed from it. No flask was com- 

 pletely free, but bacteria could be reduced to as few as five colonies 

 per ml. In the present test, the flask with antibiotic treated Gammarus be- 

 gan with about 200 colonies per ml and had 5000 by the end, as com- 

 pared with 100,000 or more in the control. Evidently the intermediar>- 

 activity of bacteria is necessary to permit inorganic phosphorus to be used. 



