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PLoS Comput Biol. 2009 Oct;5(10):e1000545. doi: 10.1371/journal.pcbi.1000545. Epub 2009 Oct 23.

Invariant distribution of promoter activities in Escherichia coli.

Author information

1
Division of Biology, California Institute of Technology, Pasadena, California, United States of America. alonzo@caltech.edu

Abstract

Cells need to allocate their limited resources to express a wide range of genes. To understand how Escherichia coli partitions its transcriptional resources between its different promoters, we employ a robotic assay using a comprehensive reporter strain library for E. coli to measure promoter activity on a genomic scale at high-temporal resolution and accuracy. This allows continuous tracking of promoter activity as cells change their growth rate from exponential to stationary phase in different media. We find a heavy-tailed distribution of promoter activities, with promoter activities spanning several orders of magnitude. While the shape of the distribution is almost completely independent of the growth conditions, the identity of the promoters expressed at different levels does depend on them. Translation machinery genes, however, keep the same relative expression levels in the distribution across conditions, and their fractional promoter activity tracks growth rate tightly. We present a simple optimization model for resource allocation which suggests that the observed invariant distributions might maximize growth rate. These invariant features of the distribution of promoter activities may suggest design constraints that shape the allocation of transcriptional resources.

PMID:
19851443
PMCID:
PMC2758578
DOI:
10.1371/journal.pcbi.1000545
[Indexed for MEDLINE]
Free PMC Article

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