Activation of amino acid transport during steady-state growth of Escherichia coli.
Accumulation of amino acids in exponentially increasing cultures of Escherichia coli was linear, supporting the interpretation that the biphasic response observed when cultures grew without these acids reflects a transient perturbation in accumulation. Rates of accumulation of glutamine, histidine and glycine were compared in steady-state and non-steady-state cultures. Their uptake rates were markedly enhanced in steady-state cultures at low exogenous concentrations, 10 microM or less. The results support the activation of amino acid transport systems by low concentrations of the particular amino acid present during growth. This activation was decreased when exogenous concentrations of the amino acid were markedly increased or when cells were washed free of the amino acid. Upon readdition of the amino acid after washing, recovery of enhanced transport required several generations, supporting a process of recovery other than enzymatic induction. The observation of amino acid enhancement of transport for eight other amino acids examined in steady-state culture suggests that this enhancement is a common process.
Kubitschek
H E
HE
Biological, Environmental and Medical Research Division, Argonne National Laboratory, IL 60439.
Pai
S R
SR
D000596:Amino Acids / Q000493:pharmacokinetics*; D001693:Biological Transport, Active / Q000502:physiology; D004926:Escherichia coli / Q000254:growth & development*; D005973:Glutamine / Q000493:pharmacokinetics*; D005998:Glycine / Q000493:pharmacokinetics*; D006639:Histidine / Q000493:pharmacokinetics*; D066298:In Vitro Techniques
D000596:Amino Acids; D005973:Glutamine; D006639:Histidine; D005998:Glycine