Environmental Control of Cell Composition in Escherichia coli

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Abstract
Escherichia coli was grown in continuous culture at various rates in a defined medium with either the carbon or the nitrogen source as rate-limiting substrate. Average cell size and the cellular content of ribonucleic-acid, protein and free amino-acids varied both with growth rate and with the identity of the limiting nutrient, being greatest at high growth rates, and greater for nitrogen-limited than for carbon-limited populations. Immuno-electrophoresis of cell extracts revealed antigenic components associated uniquely with growth rate, and others associated with the identity of the limiting nutrient on which cells had been grown. Cell composition thus appears to reflect the physiological adjustment of a microbial population to its total environment.