Aureomycin-resistant cell-free nitro reductase from aureomycin-resistant Escherichia coli.

It has previously been reported from this laboratory (Saz and Slie, 1954a) that chlortetracycline ("aureomycin") in concentrations of 1 to 100 ,ug per ml inhibited an enzyme complex from Escherichia coli strain E-26 mediating the reduction of chloramphenicol and other aromatic nitro compounds to the corresponding arylamines. The cofactor requirements for this organic nitro reductase were found to be diphosphopyridine nucleotide (DPN) and i-malic acid (replaceable by reduced DPN), -cysteine and a divalent cation (Saz and Slie, 1954b). In addition, by analogy with non-bacterial systems (Bueding and Jolliffe, 1946; Nason and Evans, 1953; Nicholas and Nason, 1955) a flavin was postulated as an intermediate carrier of electrons between the pyridine nucleotides and the nitro-amino system. In the present paper, the nitro reductase of aureomycm-resistant variants of sensitive E. coli proved resistant to aureomycin both in intact cells and cell-free extracts.