Abstract: In order to study the genetic basis and mechanism of chromate resistance in chromate resistant bacteria, conjugal transfer as well as curing of plasmids in these bacteria and its effect on chromium uptake are being investigated. From the effluent of Shafiq Tannery, Kasur, Pakistan, four bacterial strains STCr-1, STCr-2, STCr-3 and STCr-4 which could endure 40 mg mL-1 of potassium chromate in nutrient agar medium were isolated. All of them were gram negative, aerobic and motile rods. One strain STCr-1 was identified as Ochrobactrum species by 16S rRNA gene sequence homology. Each strain harboured a single conjugative plasmid, which conferred resistance to chromate. Maximum plasmid transfer was recorded after 24 h of mating except for plasmid residing in STCr-3 (pSH1322), which transferred maximally after 16 h of mating. The plasmids harboring STCr-1 (pSH1320), STCr-3 (pSH1322) and STCr-4 (pSH1323) manifested highest transfer frequency at donor:recipient ratio 1, while plasmid resident of STCr-2 (pSH1321) preferred donor:recipient ratio 5. Transfer frequency of plasmids pSH1320 and pSH1322 was maximal at 28°C and that of pSH1321 and pSH1323 at 37°C. Optimum pH for plasmid transfer was 8 for these plasmids except pSH1320, which opted for pH 6 or 7. Curing of chromate resistant plasmids from these strains was achieved with SDS at high temperature and curing of plasmid was associated with the loss of chromate resistance phenotype. A comparison of Cr uptake by the parental strains and their cured derivatives revealed that plasmids in these strains express high level resistance to chromate by exerting stringent control on the accumulation/uptake of Cr.