568 Marine Microbiology 



cial effect of sterilization by heat has been known for more than 75 

 years and was reported periodically by various investigators loca- 

 ted throughout the world (see review by Carlucci and Pramer, 

 ( 2 ) ) the identity of the factors responsible for the phenomenon 

 has not been established. Numerous suggestions have been 

 made, but few were tested experimentally. Therefore, studies 

 were initiated in this laboratory to evaluate the contribution of 

 various physical, chemical, and biological factors to the death 

 of Escherichia coli in sea water. The majority of the results have 

 been published (1, 3, 4, 5, 6, 7, 9). Although the cause of the 

 bactericidal action of sea water has not as yet been identified, 

 the work has provided some insight into the complex interactions 

 that influence gi'owth and reproduction, as well as those that con- 

 trol survival and cause death of coliform bacteria in sea water. 



The reaction, salinity, and low organic matter content of sea 

 water contribute significantly to the death of cells of E. coli in a 

 marine environment. Development of the bacterium is limited 

 also by a lack of adequate amounts of nitrogen, phosphorus, and 

 iron. The significance of biological factors has been emphasized 

 by various investigators, who postulated that competitors, preda- 

 tors, phages, and heat-labile toxic substances of biological origin 

 (antibiotics) contribute to the death of bacteria in sea water. 

 Studies in this laboratory showed that E. coli was not able to 

 compete effectively with the indigenous marine microflora for 

 organic matter added to sea water. The importance of predation 

 has not as yet been evaluated, but it was demonstrated that rea- 

 sonable levels of phages and antibiotics do not significantly in- 

 fluence the survival of E. coli in sea water unless the water is sup- 

 plemented with nutrients that support growth and multiplication 

 of the bacterium. 



Although one can visualize microhabitats and localized con- 

 ditions in which biological factors may be of considerable impor- 

 tance, it is doubtful that they contribute significantly to the bac- 

 tericidal action of sea water. It does not appear that the bac- 

 tericidal action of sea water can be explained completely or satis- 

 factorily in terms of the destruction or inactivation by heat, of 

 competitors, predators, phages, or antibiotics. Moreover, the sug- 

 gestion that the increased survival of E. coli in autoclaved water 



