Chapter V 



— 81 — 



Distribution in the Sea 



which inhibited the growth of bacteria, yeasts, and molds. Additional 

 examples of specific and indirect antagonistic efi"ects of microorganisms 

 are given by Waksman (19416). 



There are no quantitative data on the extent to which microbial an- 

 tagonism may limit the bacterial population of the sea, but the presence 

 of organic bacteriostatic substances in sea water has been definitely es- 

 tablished. It has been known since the work of de Giaxa (1889) that the 

 profuse growth of bacteria in raw sea water eventually renders it unfit as 

 a medium for the cultivation of bacteria, presumably due to the formation 

 of toxic products. According to de Giaxa (1889), Vibrio comma rapidly 

 disappeared from raw sea water, the rate of disappearance being directly 

 proportional to the abundance of other bacteria in the water, but in 

 boiled or autoclaved sea water Vibrio comma survived for a long time. 

 Similarly, Kiribayashi and Aida (1934) and Krassilnikov (1938) ob- 

 served that bacteria survived much longer in sterile than in raw sea water. 

 Prescott and Winslow (1931) give references to observations on the 

 greater longevity of the typhoid bacillus in sterile sewage as contrasted 

 with its rapid disappearance from raw sewage, which is attributed to bac- 

 terial antagonism. 



In raw water freshly collected from the Black Sea, only 1,500 Staphylo- 

 coccus aureus developed per ml. in experiments conducted by Krassil- 

 nikov (1938). Similar water previously sterilized by passage through a 

 Seitz filter or by boiling supported the growth of 860,000 and 86,000,000 

 Staph, aureus respectively. 



Sea water is rendered more growth-promoting by boiling or autoclav- 

 ing, not only because the heat treatment frees it from antagonistic micro- 

 organisms, but because it also destroys certain thermolabile toxic prod- 

 ucts. ZoBell (1936) found that sea water sterilized by filtration was ap- 

 proximately three times as toxic for coliform bacteria as was sea water 

 sterilized by heating. When coliform bacteria, confined in all-porcelain 

 Coors filter candles impregnated with collodion, were immersed directly 

 in the sea they died approximately ten times as fast as when they were 

 thus immersed in autoclaved sea water or in Berkefeld-filtered water. 

 The average results from several such experiments are recorded in Table 

 XXIII. These experiments prove that the toxic principle is thermolabile, 

 water-soluble, and tends to be adsorbed by untreated Berkefeld bougies. 



Table XXIII. — Relative numbers of coliform bacteria which survived in stoppered, collodion- 

 treated, Coors porous filter tubes when immersed in dijferent kinds of water at 16° C. (from ZoBell, 



Further experiments have shown the toxic principle to be adsorbed by 

 activated charcoal, diatomaceous earth, bentonite, and other surface- 

 active substances. Also, it is precipitated from solution by iron and alu- 

 minum salts in a slightly alkaline medium. There is a higher concentra- 

 tion of the toxic principle in polluted sea water than in sea water collected 

 from the open ocean. 



