The bacterial population of water samples from the sea, lakes or other sources usually increases during storage. While several different factors may be operative (Prescott and Winslow, 1931), it is noteworthy that the magnitude of the increase is often related to the size of the receptacle in which the water is stored. For example, Whipple (1901) found that the bacterial population of water, which initially contained an average of 77 bacteria per ml., increased to 300 per ml. in a gallon, 900 per ml. in a quart, 7,020 per ml. in a pint and 41,400 per ml. in 2-ounce bottles after 24 hours' incubation under comparable conditions. He attributed this to the greater availability of oxygen in the small receptacles which were not filled to capacity. However, ZoBell and Stadler (1940) have shown that the multiplication and respiration of aerobic bacteria is independent of the oxygen tension within the examined ranges of 0.30 to 36 mgm./liter. Using oxygen consumption as well as bacterial multiplication in glass-stoppered bottles filled to capacity with sea water as criteria, ZoBell and Anderson (1936) noted that bacteria are generally more active in small than in large receptacles of similar shape. Since the small receptacles present relatively more solid surface per unit volume of stored water than large receptacles, they concluded that solid surfaces are beneficial to bacteria in dilute nutrient solutions. A similar conclusion was reached by Lloyd (1937). The following report is concerned with the ways in which solid or adsorbing surfaces may influence bacterial activity. GLASS SURFACES ADSORB NUTRIENTS Inasmuch as the effect of volume or solid surfaces upon bacterial activity can be demonstrated only in very dilute nutrient solutions and since the effect is more pronounced with colloidal than with dissolved nutrients, ZoBell (1937) suggested that nutrients may be concentrated on solid surfaces. This explanation is supported by more recent observations here and elsewhere. The work of ZoBell and Grant (1943) shows that bacterial activity is directly proportional to the concentration of nutrients when the latter is less than 10 mgm./l. Since sea water ordinarily contains less than 5 mgm./l. of organic matter (Krogh, 1931), only a small part of which is readily attacked by bacteria (Waksman and Carey, 1935a), it follows that any factor which tends to concentrate the organic matter would promote bacterial activity. Although the small quantity and complexity of the organic content of sea water make it difficult to estimate the amount which is adsorbed by glass or other solid surfaces under different conditions, there are several ways in which Contribution from the Scripps Institution of Oceanography, New Series No. 204.

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Many micro6rganisms possess the ability of utilizing hydrocarbons as a sole source of energy in their metabolism. Gaseous, liquid and solid hydrocarbons in the aliphatic, olefinic and naphthenic series are susceptible to microbial decomposition. Nearly a hundred species of bacteria, yeasts and molds representing thirty genera have been described which attack one or more kinds of hydrocarbons. Such microbes appear to be quite widely and abundantly distributed in nature where they may be of considerable importance in the carbon cycle and to various industries. Wherever exposed to mineral solutions in which microbial life is possible, petroleum, rubber or other types of hydrocarbons may be slowly decomposed by micro6rganisms. The microbial oxidation of hydrocarbons may help to account for the rapid disappearance of petroleum which pollutes fields and waterways, for the deterioration of certain rubber products both natural and synthetic, for the spoilage of cooling oils, for the depreciation of oiled or asphalt-surfaced highways and for the modification of petroleum or its products stored in the presence of water. The failure of underground pipelines or electrical conduits "protected" from corrosion by paraffin-impregnated materials, elastomers or other hydrocarbon derivatives may be attributed in part to the activities of microorganisms which decompose hydrocarbons. Obtaining intermediate products of economic value such as fatty acids, for example, from the microbial decomposition of hydrocarbons, or employing micro-'Contribution from the Scripps Institution of Oceanography, New Series No. 295. This report represents part of the activities of Research Project 43A sponsored by the American Petroleum Institute