NRDD AND NRDG GENES ARE ESSENTIAL FOR STRICT ANAEROBIC GROWTH OF ESCHERICHIA-COLI

In Escherichia coli ribonucleotide reduction is catalyzed by two separ ate enzymes during aerobic and anaerobic growth. The aerobic enzyme is coded by the nrdAB genes, the anaerobic enzyme by nrdDG. We now show that knock-out mutants of either nrdD or nrdG cannot grow during stric t anaerobiosis, achieved by inclusion of sodium sulfide in the medium. Interestingly, these mutants grow well under microaerophilic conditio ns by overproducing the aerobic enzyme. Under such conditions wild-typ e bacteria turn off nrdAB and switch on nrdDG. (C) 1996 Academic Press , Inc.