Mutants of Escherichia coli specifically deficient in respiratory formate dehydrogenase activity.

Escherichia coli K12 mutants lacking phenazine-methosulphate-linked formate dehydrogenase (FDH-PMS) activity, but still capable of producing normal levels of benzyl-viologen-linked formate dehydrogenase (FDH-BV) and nitrate reductase activities, have been isolated following P1 localized mutagenesis. The relevant mutations mapped with the same cotransduction frequency close to the rhaD gene, at 88 min on the E. coli chromosome.

Plasmids with the uidA reporter gene for the detection of promoters and transcription signals.

We have constructed promoter-probe plasmids, pNB4 and pNB5, based on the promoterless gene for beta-glucuronidase (uidA) of Escherichia coli. Unique restriction sites for EcoRI, SacI, KpnI, SmaI, XmaI, XbaI, SalI, SphI and HindIII in pNB4 and for HindIII, PstI and BglII in pNB5 were included upstream of the uidA structural gene. The usefulness of these plasmids was demonstrated by cloning the promoter-operator region of the E.