RESPONSE OF THE MICROBIAL COMMUNITY TO THE BIOTREATMENT OF A SOIL CONTAMINATED WITH A MEDIUM CRUDE

The aim of this study was to assess the changes after 120 days in the petroleum hydrocarbon content and the activity of microbial communities in a contaminated soil (9 % w/w) with oil crude of 24.3 degrees according to the classification of the American Petroleum Institute (API). Three treatments were established: a) fertilized soil (F: contaminated soil with organic and inorganic fertilization), unfertilized soil (SF: contaminated soil without fertilization) and abiotic control (TA: contaminated soil fertilized and sterilized). The content of oils and greases, the pristane and phytane biomarkers and their relationships with hydrocarbons of 17 and 18 carbon atoms to identify biodegradation processes, basal respiration and use of specific organic substrates by microorganisms were determined. We found that the decrease in the content of oils and greases followed the order F > SF > TA. The biomarker analysis indicated that the conversion of petroleum in the fertilized treatment was higher compared to the other treatments evaluated. Differences in patterns of substrate utilization by microorganisms in treatments fertilized and unfertilized were also found with a decreased in functional diversity in treatment without fertilizer. We conclude that the functional structure of the microbial community was more stable in fertilized soil, and consequently more efficient degrading the oil crude contaminant.