Chapter VIII 



CHARACTERISTICS OF MARINE BACTERIA 



Near shore the movements of water, wind, migratory birds, and other 

 agencies provide for a continuous interchange of microorganisms between 

 the land and the sea. Since many fresh-water and soil bacteria can sur- 

 vive for prolonged periods of time in a salt concentration equal to or 

 greater than that occurring in the sea, and since bays and estuaries pro- 

 vide a gradual transition from fresh to salt water, one might expect to 

 find soil and fresh-water bacteria in the sea freely intermingled with 

 marine forms. Such a condition does prevail along the littoral zone, but 

 only to a very limited extent in the open ocean. 



Although there are no infallible criteria for the differentiation of 

 marine from non-marine bacteria, most of the bacteria which occur in the 

 open ocean differ in certain respects from those found in non-marine 

 habitats. This is probably because adventitious organisms either fail to 

 perpetuate themselves in the marine environment or else lose their iden- 

 tity in becoming acclimatized thereto. 



Unfortunately there have been no comprehensive studies of the general 

 characteristics of marine bacteria as a group, although the observations of 

 Russell (1891), Fischer (1894a), Issatchenko (1914), Bavendamm 

 (1932), Benecke (1933), Waksman and coworkers (1932-36), and Bed- 

 ford (1933a, h) are informative. The generalizations recorded below are 

 based upon the published reports of these and other workers together with 

 our own observations. 



Cell morphology : — About 80 per cent of the marine bacterial species 

 catalogued by ZoBell and Upham (1944) are Gram-negative rods. From 

 the random examination of colonies which developed on plates as well as 

 from the direct microscopic examination of marine materials stained by 

 the method of Gram, it is estimated that approximately 95 per cent of the 

 bacteria occurring in the sea are Gram-negative. This compares favor- 

 ably with the percentage of Gram-negative bacteria found in bodies of 

 fresh water by Taylor (1942), and is more than twice as many as Taylor 

 and LocHHEAD (1938) found in soil (see Table XXXI). 



Apparently there are proportionately more cocci in soil than in 



Table XXXI. — Comparison of main morphological groups of bacteria in soil, lake water, 

 and marine materials: — 



' 625 soil cultures examined by Taylor and Lochhead (1938). 



' 209 soil cultures examined by Topping (1Q37). 



' 671 cultures from fresh-water lakes examined by Taylor (1942). 



< 7S0 cultures from sea water and marine mud examined by ZoBell et at. 



