ISOLATION, CHARACTERIZATION AND EXPRESSION OF A PLASMID ENCODING CHROMATE RESISTANCE IN PSEUDOMONAS-PUTIDA KT2441

The chromium resistance properties encoded by a natural plasmid recove red from the environment were investigated. A 200 kb plasmid was isola ted by the exogenous plasmid isolation method. The plasmid conferred a chromate resistance phenotype (MIC 8 mmol l(-1)) to a chromate suscep tible strain of Pseudomonas putida KT 2441 (MIC 0.5 mmol l(-1)). The r esistant strain took up 50% less Cr-51 than the isogenic susceptible s train of Ps. putida KT2441. In addition, the resistant strain expresse d two new membrane proteins encoded by the plasmid, an outer membrane protein (molecular weight 60 000) and an inner membrane protein (molec ular weight 35 000). The physiological significance of these proteins is under current investigation.