ZoBell — 146 — Marine Microbiology 



more readily by lipoclastic anaerobes than is either fatty acid alone. In 

 long-term experiments with mixed cultures of lipoclastic anaerobes growing 

 on lipid-rich algae from Mission Bay, a significant increase in the content 

 of ether-soluble, unsaponifiable material was observed, thereby indicat- 

 ing that lipids may be converted into hydrocarbons or hydrocarbon-like 

 substances. The unsaponifiable material is a waxy substance which 

 gives no colorimetric indications for the presence of sterols. 



Working on the hypothesis that petroleum is formed from the fats and 

 oils of diatoms, Thayer (1931) found that, while marine bacteria may at- 

 tack various kinds of fats, the only hydrocarbon resulting from the action 

 of mixed cultures of marine anaerobes on fatty acids is methane. Acetic, 

 propionic, butyric, valeric, caproic, heptylic, lauric, palmitic, margaric, 

 and stearic acids were found to be decomposed quantitatively to CO2 and 

 methane by anaerobic organisms occurring in fresh-water and marine 

 muds. The formation of methane from fatty acids has been reported by 

 CooLHAAS (1928), Tarvin and Buswell (1934), and others. Most 

 marine aerobes are able to assimilate some of the fatty acids, and all 

 simple fatty acids are utilized by marine bacteria of one species or 

 another. 



Ginsburg-Karagitscheva and Rodionowa (1935) noted an abun- 

 dance of both aerobic and anaerobic lipolytic bacteria in mud from the 

 Black Sea. They found one organism which reduced the iodine number 

 of fats and produced unsaponifiable substances. Sturm and Orlova 

 (1937) isolated aerobic bacteria from Ala-Kule Lake in Russia which at- 

 tacked fats and palmitic acid with the production of CO2 and other inter- 

 mediate products. 



ZoBell and Upham (1944) described 13 species of marine lipolytic 

 bacteria. Pseudomonas enalia, Fs. felthami, Sarcina pelagia, Vibrio algo- 

 sus, Serratia marinorubra, and Bacillus submarinus were especially active 

 in attacking triglycerides. 



The ability of the sulfate reducer to oxidize fats and olive oil was 

 demonstrated by Seliber (1928). More recent observations (Baars, 

 1930) suggest that various strains of sulfate reducers can be differentiated 

 upon a basis of their ability to utilize various fatty acids. The marine 

 strain commonly known as Desulfovibrio aestuarii utilizes most of the 

 fatty acids ranging from acetic to stearic. Reports from microbiologists 

 working under the auspices of the American Petroleum Institute at the 

 Scripps Institution of Oceanography indicate that certain strains of 

 D. aestuarii produce ceresin wax and other hydrocarbon-like substances 

 from fatty acids (Jankowski and ZoBell, 1944). 



Hecht (1934) buried the bodies of invertebrates, birds, and mammals 

 in perforated celluloid boxes in different sedimentary environments and 

 examined specimens for changes over a period of three years. Fats were 

 found to be far more resistant to attack than proteins, and were still more 

 slowly decomposed in a reducing environment. 



Bacterial oxidation of hydrocarbons : — Petroleum consists primarily 

 of hydrocarbons which are believed to have been formed in the sea, 

 probably from the reduction of organic matter in anaerobic bottom de- 

 posits. There are many ways in which bacteria may be instrumental in 

 the formation and accumulation of petroleum hydrocarbons. Bacteria 

 also destroy hydrocarbons under certain conditions. Besides their rela- 

 tion to the petroleum problem, hydrocarbon-oxidizing bacteria play an 

 important role in the carbon cycle. 



