Escherichia coli mutant strain with altered expression of the tryptophan operon: isolation and preliminary characterization.

AUTOR(ES)

Pouwels, P H

RESUMO

From a strain of Escherichia coli with two copies of the tryptophan (trp) operon and one copy of the lactose (lac) operon, under control of one of the trp regulatory elements, we have isolated a mutant which does not grow in a medium containing 19 amino acids, unless tryptophan is added, and which cannot ferment lactose. The apparent pleiotropic nature of the mutation(s) is indicated by the very slow growth of mutant bacteria on minimal-medium agar supplemented with glucose and tryptophan. The amount of the trp enzymes (anthranilate synthetase and tryptophan synthetase) and trp messenger ribonucleic acid is reduced several-fold in the mutant compared to the isogenic wild-type strain, whereas the enzymes tryptophanyl-transfer ribonucleic acid synthetase and glucose 6-phosphate dehydrogenase remain the same. The incorporation of radioactive label into pulse-labeled but not into stable ribonucleic acid is significantly lower. Our results suggest that in the mutant organism the control of transcription of some operons, including the trp operon, is modified. An alternative explanation is that mutant bacteria contain a ribonuclease with increased activity for some messenger ribonucleic acid species.

Documentos Relacionados

• Escherichia coli mutant strain with altered expression of the tryptophan operon: ribonucleic acid synthesis in vitro.
• Attenuation in the Escherichia coli tryptophan operon: role of RNA secondary structure involving the tryptophan codon region.
• Escherichia coli mutant with altered respiratory control of the frd operon.
• Isolation and characterization of mutant strains of Escherichia coli altered in H2 metabolism.
• Detection and Isolation of the Repressor Protein for the Tryptophan Operon of Escherichia coli