ULTRAVIOLET ACTION SPECTRUM (238-405 NM) FOR INHIBITION OF GLYCINE UPTAKE IN ESCHERICHIA-COLI

Abstract— Initial rate of uptake of 3H‐glycine by Escherichia coli B/r was measured immediately after irradiation with monochromatic light. Uptake was proportional to time for at least 2 min in both control and irradiated samples. Inhibition of uptake is an exponential function of fluence to about 20% remaining activity, beyond which it is much more resistant to irradiation, suggesting two different uptake systems. The principal (sensitive) system shows an F37 of 2.2 kJ/m2 at 280 nm and 110 kJ/m2 at 334 nm. The response is independent of cell killing and of presence of the rel gene. The chromophore remains unidentified, although an action spectrum suggests a protein chromophore in the far‐UV (below 300 nm) region and a menaquinone chromophore in the near‐ultraviolet (above 300 nm). A 10–20%, stimulation of uptake rate, which we cannot account for, is observed at low fluences (generally below 100 kJ/m2) at 313, 366 and 405 nm, but not at 334 nm. Copyright © 1979, Wiley Blackwell. All rights reserved