In addition, different hydrocarbon-degraders came to power in the following turn. At the first stage, the Alcanivorax-related Gammaproteobacteria bacteria dominated in the biostimulated soil and contributed mainly to the biodegradation of easily degradable portion of the heavy crude oil. Then the bacteria belonging to Alphaproteobacteria, followed by bacteria belonging to Candidate division OD1, became the dominant oil-degraders to degrade the remaining recalcitrant constituents of the heavy crude oil.