Bleomycin-induced beta-lactamase overexpression in Escherichia coli carrying a bleomycin-resistance gene from Streptomyces verticillus and its application to screen bleomycin analogues.

A bleomycin-resistance gene, designated blmA, has been cloned from bleomycin-producing Streptomyces verticillus by Sugiyama et al. (Gene 151 (1994) 11-16). The present study shows that Escherichia coli harboring the blmA-carrying pUC plasmid overproduced beta-lactamase, encoded by an ampicillin-resistance gene on the plasmid, when cultured in the presence of bleomycin, which suggests that bleomycin may act as an inducer (or an activator) for the expression of the specific gene in the presence of blmA. We constructed a vector, designated pMAB50, which senses bleomycin and produces a pigment, using blmA and a Streptomyces tyrosinase gene located under the control of beta-lactamase promoter: E. coli harboring pMAB50 produced the melanin pigment in the presence of bleomycin-type antibiotics, suggesting that the transformed E. coli can be employed as a reporter organism to screen bleomycin analogues.