ZoBeU 



84 



Marine Microbiology 



mitted the entrance of small predatory animals. When introduced from 

 plankton tows into such bottles, protozoans and copepods survived with- 

 out having any noticeable effect upon the bacterial population within the 

 limits of hundreds to hundreds of thousands of bacteria per ml. of water. 



After observing that bacteria multiply proportionately faster in small 

 receptacles than in larger ones, Whipple (1901) concluded that the avail- 

 ability of oxygen was the responsible factor. When the receptacles are 

 only partly filled with water, proportionately more of the water is exposed 

 to the atmosphere when it is stored in small receptacles than when it is 

 stored in larger receptacles of similar shape. However, ZoBell and 

 Stabler (1940&) have shown that the multiplication and respiration of 

 aquatic bacteria are independent of the oxygen tension throughout the 

 range of from 0.30 to 36 mgm./liter. 



ZoBell and Anderson (1936a) confirmed Whipple's observation that 

 bacteria multiply in water stored in small receptacles appreciably faster 

 than in identical water stored in larger receptacles of similar shape. After 

 proving that neither temperature nor oxygen tension is responsible for the 

 observed phenomenon, the increased bacterial activity was attributed to 

 the beneficial effect of solid surfaces of the receptacles in which the water 

 was stored. The beneficial effect of added glass beads, ignited sand, and 

 other inert particulate materials substantiated this conclusion, which has 

 also been confirmed by the observations of Lloyd (1937). 



In dilute nutrient solutions such as sea water which contain less than 

 10 mgm. of organic matter per liter, sohd surfaces promote the multiphca- 

 tion of bacteria. This is illustrated by the data in Table XXIV obtained 

 by storing sea water in glass-stoppered Pyrex bottles for two weeks at 

 16° C, after which bacterial populations and oxygen consumption were 

 measured. 



Table XXIV. — Number of bacteria found in sea water, which initially contained 276 bacteria 

 per ml., after two weeks storage in the dark at 16° C. in glass-stoppered bottles of diferent capaci- 

 ties. The area of glass exposed to the water and the ratio of volume in ml. of water to the area 

 of glass surface are also given {from ZoBell and Anderson, igj6a): — 



Solid surfaces promote activities of bacteria in dilute nutrient solutions 

 primarily by adsorbing organic matter, thereby making it more available 

 to bacteria. ZoBell (19436) has presented chemical and biological evi- 

 dence that glass and other inert solids adsorb measurable quantities (2 to 

 27 per cent) of the organic matter in sea water. 



After observing the accumulation of organic matter on chemically 

 cleaned glass slides, Stark et al. (1938) expressed the belief that adsorbed 

 organic nutrients favor bacterial growth. Corroborative evidence is 

 given by the studies of Heukelekian and Heller (1940) on the relation 

 between food concentration and solid surfaces. In their experiments, 

 Escherichia coli failed to multiply when the concentration of food was less 

 than 0.5 p. p.m. unless glass beads were added to provide adsorbing sur- 

 faces. The beneficial effect of glass beads was noticed in solutions con- 

 taining up to 25 p. p.m. of nutrients, above which concentration soHd 



