Regulatory perturbations of ribosome allocation reshape the growth proteome with a trade-off in adaptation capacity

Abstract

SummaryBacteria regulate their cellular resource allocation to enable fast growth-adaptation to a variety of environmental niches. We studied the ribosomal allocation, growth and expression profiles of two sets of fast-growing mutants of Escherichia coli K-12 MG1655 in glucose minimal medium. Mutants with only 3 of the seven copies of ribosomal RNA operons grew faster than the wild-type strain in minimal media and show similar phenotype to previously studied rpoB mutants. Higher growth rates due to increased ribosome content affected resource allocation. Expression profiles of fast-growing mutants shared downregulation of hedging functions and upregulated growth functions. Mutants showed longer diauxic shifts and reduced activity of gluconeogenic promoters during glucose-acetate shifts, suggesting reduced availability of the RNA Polymerase for expressing hedging proteome. These results show that the regulation of ribosomal allocation underlies the growth/hedging phenotypes obtained from laboratory evolution experiments. We show how two different regulatory perturbations (rRNA promoters or rpoB mutations) reshape the proteome for growth with a concomitant fitness costHighlightsMutants with only 3 ribosomal operons grow faster than wild-type in minimal mediumΔ4 rrn and rpoB mutants share phenotypic traitsFaster growth of mutants is achieved by increased ribosome contentFast-growing mutants display reduced hedging expression and adaptation trade-offsDespite similar ribosomal content in rich medium the mutants present growth defects