A wide variety of metabolic and physiological factors are required for the degradation of different compounds in diesel oil (Frielo et al., 2001). All of such properties are not found in one organism.Monocultures can be adversely affected by negative interactions. The best approach would be the use of a consortium of microorganisms. By selecting a consortium from a contaminated environment,the negative interactions could be minimal. Moreover,the microorganisms will readily adjust to the contaminated environment. In our work, the best effect on lowering the surface tension was observed
when bacterial isolates were mixed. One consortium of isolates from a Long Beach soil sample decreased the surface tension to 41.4mMm1 and increased the emulsion index by 64% after 24 h.