Bleomycin-induced gene expression in E.coli carrying blmA gene

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A bleomycin (Bm)-producing microorganism, Streptomyces verticillus ATCC15003 possesses two Bm resistance genes designated blmA and blmB.When one of these genes, designatedblmA,was inserted into pUC18 (or pUC19) plasmid and introduced into Escherichia coli TG1, the transformed cells expressed high level-resistance to Bm. In the present study we show that E.coli harboring the blmA-encoding pUC vector overproduced a 30-kDa protein when cultured in the presence of Bm. The Bm-induced protein was identified as the beta-lactamase encoded by the ampicillin resistance gene on the plasmid. In addition, we found that although the Bm family such as pepleomycin, phleomycin, cleomycin and liblomycin gave rise to beta-lactamase induction, bleomycininc acid which lacks terminal amine moiety in Bm molecule, did scarcely. We propose a hypothesis that Bm, an antibiotic inhibitor of DNA synthesis, acts as a an inducer (or an activator) for the expression of a specific gene in the presence of blmA.On the other hand, we constructed a chimeric plasmid designatd as intelligent vector pMAB70, which carried blmA and a tyrosinase structual gene put under the control of beta-lactamase promoter. E.coli harboring pMAB70 produced the melanine pigment, when cultured in the presence of Bm.