A role for a conserved kinase in the transcriptional control of methionine biosynthesis in Escherichia coli experiencing sustained nitrogen starvation

Abstract

The initial adaptive transcriptional response to nitrogen (N) starvation in Escherichia coli involves large-scale alterations to the transcriptome mediated by the transcription activator, NtrC. One of the NtrC-activated genes is yeaG, which encodes a conserved bacterial kinase. Although it is known that YeaG is required for optimal survival under sustained N starvation, the molecular basis by which YeaG benefits N starved E. coli remains elusive. By combining transcriptomics with targeted metabolomics analyses, we demonstrate that the methionine biosynthesis pathway becomes transcriptionally dysregulated in{Delta} yeaG bacteria experiencing sustained N starvation. This results in the aberrant and energetically costly biosynthesis of methionine and associated metabolites under sustained N starvation with detrimental consequences to cell viability. It appears the activity of the master transcriptional repressor of methionine biosynthesis genes, MetJ, is compromised in{Delta} yeaG bacteria under sustained N starvation, resulting in transcriptional derepression of MetJ-regulated genes. The results suggest that YeaG is a novel regulatory factor and functions as a molecular brake in the transcriptional control of both the NtrC-regulon and methionine biosynthesis genes in E. coli experiencing sustained N starvation.