Mineralization of [14C]hexadecane and [14C]phenanthrene in crude oil: specificity among bacterial isolates

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Abstract
Bacteria isolated from freshwater, marine, and estuarine samples were tested for the ability to produce 14CO2 from n-[1-14C]hexadecane or [9-14C]phenanthrene added to Prudhoe Bay crude oil. Of 138 isolates tested, 54 (39%) mineralized the model aliphatic compound hexadecane and 6 (4%) mineralized the model aromatic compound phenanthrene. None mineralized both compounds. There was no apparent correlation between degradative ability and genus or source. Additional hydrocarbon-degrading bacteria from diverse sources were tested and found to mineralize either hexadecane or phenanthrene. Of 61 hexadecane- and 21 phenanthrene-mineralizing bacteria tested, none mineralized both model compounds. Selected isolates and commercially available cultures were tested for mineralization of specific 14C-labelled mono-, di-, and tri-cyclic aromatics. An apparent hierarchy of degradation was observed: strains mineralizing the mono- and di-cyclic aromatics toluene and naphthalene did not mineralize biphenyl or the tricyclic aromatics anthracene and phenanthrene, whereas those strains that mineralized the tricyclic aromatics also mineralized the smaller substrates. Similarly, not all n-alkane-mineralizing isolates tested mineralized the isoprenoid pristane. A combined culture consisting of one aliphatic- and one aromatic-degrading isolate was tested for mineralization of the model compounds and for degradation of other crude oil components by gas chromatography. No synergism or antagonism was observed compared with degradation by the individual isolates. Key words: aromatic, aliphatic, bioegradation, petroleum.