HISTIDINE-REQUIRING MUTANTS OF ESCHERICHIA COLI K12

Genetic analysis of the histidine operon in Escherichia coli K12.

I N Salmonella typhimurium a cluster of nine genes, behaving as a single operon (AMES and GARRY 1959) specify the enzymes which carry out the ten reactions involved in the biosynthesis of histidine; one of the nine enzymes is bifunctional (LOPER, GRABNAR, STAHL, HARTMAN and HARTMAN 1964). The histidine operon is contained in a linear segment of deoxyribonucleic acid (DNA) estimated by AMES, GOL...

Isolation and characterization of cysK mutants of Escherichia coli K12.

cysK mutants, deficient in O-acetylserine sulphydrylase A [O-acetyl-L-serine acetate-lyase (adding hydrogen-sulphide); EC 4.2.99.8], were isolated as strains resistant to selenite or giving a black colour reaction on bismuth citrate indicator medium. All were resistant to the inhibitor I,2,4-triazole. Four independent mutants were found which possessed lowered levels of O-acetylserine sulphydry...

Plasmid-instability in acrA mutants of Escherichia coli K12.

Thymineless death in recombination deficient mutants of Escherichia coli K12.

When grown in thymine-free minimal synthetic medium, thyA recA mutants of Escherichia coli K12 were comparatively more resistant and thyA recBC mutants more sensitive to thymineless death (TLD) than their respective parent strains. No excessive numbers of single-strand breaks were observed in the DNA of the recBC mutant strain starved for thymine, hence the hypersensitivity for TLD in this stra...

Intracellular thymidine triphosphate concentrations in wild type and in thymine requiring mutants of Escherichia coli 15 and K12.

The intraoellular concentration of thymidine triphosphate has been measured in thymine requiring mutants of Escherichia co&i K12 and E. coli 15, and compared with that in non-mutant strains using thymine, thymidine and a mixture of thymine and deoxyguenosine, in the growth medium. The data show (1) that the thymidine triphosphate concentration rises as the thymine concentration in the growth me...