Growth of hydrocarbon-utilizing isolates in chemically defined media

Five different bacterial strains isolated from oil-contaminated soil adhered to suspended droplets of Jet A fuel, but the adhesion did not correlate with the observed growth rates on this fuel. Growth rates were monitored by observing optical density (OD546) and total protein in liquid cultures as well as reduction of 2,3,5-triphenyl tetrazolium chloride (TTC) to formazan in liquid and agar cultures. Either preconditioning to hydrocarbons or direct aeration of the culture medium, significantly increased the extent of growth of each isolate over several days. Jet-A fuel and motor oil were found to serve as a source of carbon and energy for each of these strains. Conversely, brake fluid did not support growth of any of these strains. The growth of one strain (SBI-5) on hydrocarbons predominated over the other four. Growth of SBI-5 on Jet-A fuel or motor oil was accompanied by production of emulsification activity.