The Bactericidal Action of Sea Water 569 



was due to the ability of heat to disrupt and degrade microbial 

 cells and thermolabile compoiuids, and thereby, to cause an in- 

 crease in concentration of available nutrients in sea water was 

 tested. Although added organic matter favored the survival of 

 E. coli in sea water, the minimum nutrient level required to off- 

 set the bactericidal action was greater than that which would be 

 provided by the heat treatment. 



Artificial sea water formulated in the laboratory to contain 

 no competitors, predators, phages, antibiotics, or organic nu- 

 trients exerted a bactericidal action comparable to that of natural 

 sea water. However, it is not possible at this time to conclude 

 that the factors responsible for the bactericidal action of artificial 

 sea water are identical with tliose responsible in natural sea 

 water. Present experience indicates that the bactericidal action 

 of sea water is a complex phenomenon. It appears to be due to 

 a combination of factors and the contribution of each to the over- 

 all effect may vary with the time and site of sampling. This is 

 illustrated by the results of an experiment in which the survival 

 of cells of £. coli in untreated, filtered, and autoclaved portions of 

 each of six different water samples was determined (Table 1). 

 In each of the six samples E. coli died more rapidly in untreated 

 than in autoclaved water, but the magnitude of the bactericidal 

 action varied greatly. Likewise, the influence of filtration was not 

 constant. In four of the six samples, survival of the test organism 

 was significantly greater in filtered than in untreated water. If it 

 is assumed that the beneficial effect of filtration resulted from 

 removal of competitors and predators, then their numbers and 

 activities varied from sample to sample. The decreased survival 

 of E. coll in the filtered portion of water sample 5 (Table 1) can 

 be explained by the possible but improbable assumption that a 

 beneficial substance or organism was removed by filtration. In 

 two of the six samples (numbers 1 and 6) survival of £. coli was 

 the same in filtered and autoclaved water and the bactericidal 

 action may be fully accounted for by competitors and predators 

 that were eliminated by filtration. In two other samples (numbers 

 3 and 5 ) filtration did not influence survixal and it appeared un- 

 likely that competition and predation contributed significantly to 

 the death of cells in the untreated water. In four of the six samples 



