The Hydrocarbon-Oxidizing Bacteria
The chemical heterogeneity and water insolubility of hydrocarbons pose special problems for microorganisms that must use these substances as nutrients. In an attempt to define a petroleum-degrading bacterium, Gutnick and Rosenberg (1977) postulated three
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The Hydrocarbon-Oxidizing Bacteria EUGENE ROSENBERG and DAVID L. GUTNICK
The chemical heterogeneity and water insolubility of hydrocarbons pose special problems for microorganisms that must use these substances as nutrients. In an attempt to define a petroleum-degrading bacterium, Gutnick and Rosenberg (1977) postulated three distinguishing traits or specificities: 1. Efficient hydrocarbon uptake system (special receptor sites for binding hydrocarbons and/or production of unique chemicals that assist in the emulsification and transport of hydrocarbons into the cell). 2. Group-specific oxygenases (genetic potential of a particular microorganism to introduce molecular oxygen into the hydrocarbon and, with relatively few reactions, generate intermediates that subsequently enter common energy-yielding catabolic pathways). 3. Inducer specificity (the positive response of the organism to petroleum and its constituents in inducing the first two systems; inducer specificity and substrate specificity for oxygenase need not coincide). The various means by which different microorganisms have evolved specific solutions to these three problems probably account for the fact that over 200 different species of eukaryotic and prokaryotic hydrocarbon-utilizing microorganisms have been described (Beerstecher, 1954; ZoBell, 1973). This chapter will be restricted to the hydrocarbondegrading bacteria, exclusive of the specific classes of methane oxidizers.
Habitats Hydrocarbons are a ubiquitous class of natural compounds. Not only are they found in petroleumpolluted areas, but chemical analyses have revealed the presence of significant quantities of aliphatic and aromatic hydrocarbons in most soils and sediments (Bergmann, 1963; Giger and Blumer, 1974; Stevenson, 1966). The probable origin of the low concentrations of widely distributed hydrocarbons is ongoing biosynthesis by certain plants and microorganisms (Fehler and Light, 1970; Juttner, 1976; M. P. Starr et al. (eds.), The Prokaryotes © Springer-Verlag Berlin Heidelberg 1981
Kolattukudy, Buckner, and Brown, 1972; Mikkelsen and Von Wettstein-Knowles, 1978; Winters, Parker, and Van Baalen, 1969). It is therefore not surprising that hydrocarbon-oxidizing bacteria are widely distributed in nature. In fact, Jones and Edington (1968) reported that 1- 10% of bacterial isolates from noncontaminated soils were capable of growing on hydrocarbons as the sole source of carbon and energy. A sample of ecological studies on hydrocarbondegrading bacteria is shown in Table 1. It can be seen that hydrocarbon oxidizers are located in virtually all natural areas, although with large variations in cell concentration. As would be expected, the ratio of hydrocarbon-oxidizing bacteria to the total population of heterotrophic bacteria, as well as the variety of hydrocarbon-degrading microorganisms found in a particular ecosystem, may change according to the time of sampling or the extent of oil pollution. ZoBell (1969) has discussed many of the factors that limit the growth of hydrocarbonoxidizing bact
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