Classification and Identification of Petroleum Microorganisms by MALDI-TOF Mass Spectrometry

Indigenous bacteria isolated from a crude oil sample from a deep water reservoir in the Pampo Sul Oilfield (Campos Basin-RJ, Brazil) were previously classified as strains of B. pumilus. However, their enzymatic activities with fluorogenic probes and rates of petroleum biodegradation were completely different. Some of the bacteria depleted n-alkanes, whereas others did not. Aromatic compounds reported to be recalcitrant were also biodegraded by some of these Bacillus strains, revealing their outstanding ability to deplete petroleum. Further classification using matrixassisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) followed by statistical analysis revealed that these strains could be clustered into three different groups, consistent with their enzymatic activity evaluation. A more accurate phylogenetic analysis using gyrB gene sequences confirmed the MALDI-TOF MS classification of three groups of strains and identified them as Bacillus safensis, B. cereus and B. thuringiensis.