576 



Marine Microbiology 



0.3 r 



Fig. 2. Growth of S. marinorubra at 37 C in artificial sea water, and sea 

 water collected from a depth of 100 meters. The 100-meter sea water was 

 filter-sterilized and stored for one week at 4 C before being tested. The 

 test was carried out in 90 per cent sea water supplemented with Medium II. 



samples also were found to contain properties suppressing growth 

 of B. siibtilis, E. coli, and S. marinorubra. S. aureus, however, 

 was slightly stimulated by all of the pelagic seawater samples. 

 All of the test bacteria were inhibited to a greater extent by tlie 

 bottom water than by any of the pelagic samples. In Experiment 

 II, there was no appreciable increase of the inhibitory effect with 

 the depth of the pelagic samples. 



Although not shown in Figure 1 , 16 units of penicillin G per 

 ml of artificial sea water were added as an additional comparison 

 in Experiment II. The natural sea-water samples were more in- 

 hibitory to B. suhtilis, E. coll, and S. marinorubra than was peni- 

 cillin at this concentration. 



Terminal growth was determined by the experimental pro- 

 cedures described, prior to evidence for autolysis. Figure 2 shows 

 a comparison between growth curves of S. marinorubra in media 

 prepared with artificial sea water, and in media prepared witli 



