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A strain able to grow up m-toluate minimal medium has been isolated after selective enrichment and given the name T81X, which was later identified as pseudomonase putida according to its morphological and biochemical characteristics. After treatment with plasmied specific curing agent, mitomycin C, followed by replica plating on m-toluate and xylene minimal agar plate, T81Xstrain has been shown to harbour a curable plasmid relating to the m-toluate and xylene metabolism. Spontaneous curing frequency of this plasmid was also greatly enhanced by growing on benzoate minimal medium. After then, it was also xylene metabogrowing on benzoate minimal medium. After then, it was found to be conjugally nontransmissible. From the comparative investigation of catechol 1,2-oxygenase and catechol 2,3-oxygenase activities in wild type and cured strain on various growth substrate, it appeared that T81X strain has both of these two enzymes while cured strain has catechol 1,2-oxygenase only. Growing on m-toluate minimal medium T81X strain should carry the genetic information necessary for coding the catechol 1,2-oxygense induced by m-toluate or benzoate, on that curable plasmid.
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