Chapter 52 



The Bactericidal Action of Sea Water* 



David Pramer, A. F. Carlucci and P. V. Scarping 



G 



reat numbers of bacteria enter the oceans by way of surface 

 drainage and sewage outfalls, but as one proceeds outward from 

 land a rapid decrease in numbers of bacteria in the water is ob- 

 served. ZoBell ( 10 ) estimated that tlie daily flow of sewage into 

 the Pacific Ocean along the west coast of North America carries 

 approximately 2 x 10^^ colifonn bacteria. This number, if dis- 

 tributed unifonnly to a depth of 100 m in all offshore water along 

 the continental slope, is sufficient to give a concentration of coli- 

 form bacteria of about 50 per ml. However, few if any are found 

 except in the vicinity of the source material. Dilution, adsorption, 

 aggregation, and sedimentation contribute to the decrease in 

 bacterial counts, whereas death of the coliform organisms is 

 attributed to predation, starvation, and the bactericidal action 

 of sea water. 



Ketchum, Ayers, and Vaccaro (8) determined the relative 

 significance of dilution, predation, and the bactericidal action of 

 sea water in reducing the number of coliform bacteria in a tidal 

 estuaiy. More than 99 per cent of the decrease in coliform count 

 was accounted for, and the bactericidal action of the water was 

 the most important factor contributing to the result. 



The bactericidal action of sea water is measured as the dif- 

 ference in survival of bacterial cells in untreated and autoclaved* 

 portions of the same water sample, and it has been observed 

 repeatedly that bacteria sur\ ive to a greater extent in heat-steri- 

 hzed sea water than in untreated sea water. Althoudi the benefi- 



* Paper of the Journal Scries. New Jersey Agricultural Experiment Station, De- 

 partment of Agricultural Microbiology, New Brunswick, New Jersey. This in- 

 vestigation was supported in part by Research Grant E1437 from the National 

 Institute of .\llergy and Infectious Diseases, National Institutes of Health, U. S. 

 Public Health Service. 



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