Fifty different soil samples (contaminated and uncontaminated with hydrocarbons compounds) were collected from different places in Iraq.Twenty five isolates showed the ability to utilize methanol as a sole source of carbon and energy. These isolates were repeatedly tested in the defined medium supplemented with methanol to ensure methanol utilizing ability, then only 12 isolates that appeared, really have the ability to utilize methanol and were named as (HK1,HK2,……,HK12), it was found that these isolates were varied in their growth density in utilizing methanol. Three isolates (HK8, HK9, and HK11) were selected as the efficient isolates.The efficient isolates were identified by morphological cultural characterization and biochemical tests, the results showed that two isolates belong to Pseudomonas aeruginosa (HK8, HK9) while the other one belongs to Micrococcus (HK11).Ability of bacterial isolates to utilize high concentration of methanol was done by growing these isolates on serial concentration of methanol to choose the most efficient isolate which is able to survive at the highest concentration, results indicated that P. aeruginosa HK8 was the most efficient isolate in utilizing 0.8% (v/v) methanol.Agarose gel electrophoresis of whole DNA of the three efficient isolates showed that these isolates harbored two plasmid bands.Curing experiments by SDS for the chosen isolate (P. aeruginosa HK8) showed that some colonies have lost their ability to utilize methanol as a sole carbon source .Plasmid DNA extraction from these colonies indicated the loss of plasmids.Transformation experiments for this isolate indicated that the gene(s) responsible for methanol utilization were located on plasmids after their expression in E. coli DH5? ,these results were confirmed by data obtained from curing experiments as mentioned above.