The dsz desulfurization gene cluster from Rhodococcus erythropolis strain KA2-5-1 was transferred into R. erythropolis strain MC1109, unable to desulfurize light gas oil (LGO), using a transposon-transposase complex. As a result, two recombinant strains, named MC0203 and MC0122, were isolated. Resting cells of strain MC0203 decreased the sulfur concentration of LGO from 120 mg l(-1) to 70 mg l(-1) in 2 h. The LGO-desulfurization activity of strain MC0203 was about twice that of strain MC0122 and KA2-5-1. The 10-methyl fatty acids of strain MC0203 were about 28%-41% that of strain MC1109. It is likely that strain MC0203 had a mutation involving alkylenation or methylation of Delta9-unsaturated fatty acids caused by the transposon inserted in the chromosome, which increased the fluidity of cell membranes and enhanced the desulfurization activity.