Altered regulation of macromolecular synthesis in methionine-inhibited cultures of Pseudomonas fluorescens UK1

Abstract

Effects of high methionine concentrations on growth of Pseudomonas fluorescens UK1 are reported. The following phenomena were observed: ( i) Immediate inhibition of growth for a period corresponding to approximately half a generation. Steady-state conditions of growth were no more attained. ( ii) In spite of stringency of the macromolecular synthesis in this organism, simultaneously with the growth inhibition, the rate of labelled leucine incorporation into trichloroacetic acid (TCA)-insoluble material was reduced 60% while the rate of labelled uracil incorporation remained constant. ( iii) The organism began to liberate methanethiol half a generation after the methionine supplement. Demethiolating activity increased linearly with the cell mass. It is concluded that the inhibition of growth is not due to the liberation of methanethiol from methionine but the amino acid is able to uncouple the mechanism coordinating protein and RNA synthesis in P. fluorescens UK1.