Summary
Bacteria 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 cost
Highlights Mutants with only 3 ribosomal operons grow faster than wild-type in minimal medium
Δ4 rrn and rpoB mutants share phenotypic traits
Faster growth of mutants is achieved by increased ribosome content
Fast-growing mutants display reduced hedging expression and adaptation trade-offs
Despite similar ribosomal content in rich medium the mutants present growth defects
Competing Interest Statement
B.P. is inventor in a US patent filed by UCSD concerning the rpoB mutant strains
Footnotes
We have incorporated suggested revisions: Title, figures, few new results and discusion.
https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE180830