Escherichia coli

Microbiol. Res. (2002) 157, 257–265 http://www.urbanfischer.de/journals/microbiolres

Control of Escherichia coli growth rate through cell density
Xavier Carbonell3, José Luis Corchero4, Rafael Cubarsí2, Pau Vila5, Antonio Villaverde1,2
Institut de Biotecnologia i de Biomedicina and Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra 08193 Barcelona, Spain 2 Departament de Matemàtica Aplicada i Telemàtica, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain Present addresses: 3 Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA 4 Departament de Biologia Molecular. Biokit, S.A. 08186 Lliçà d’Amunt, Barcelona 5 Departament d’Enginyeria Química, Universitat Autònoma de Barcelona, Bellaterra 08193 Barcelona, Spain XC and JLC have equally contributed to this work. Accepted: August 1, 2002
1

Abstract
The transition from the exponential to the stationary phase of Escherichia coli cultures has been investigated regarding nutrient availability. This analysis strongly suggests that the declining of the cell division rate is not caused by mere nutrient limitation but also by an immediate sensing of cell concentration. In addition, both the growth rate and the final biomass achieved by a batch culture can be manipulated by altering its density during the early exponential phase. This result, which has been confirmed by using different experimental approaches, supports the hypothesis that the E. coli quorum sensing is not only determined by the release of soluble cell-to-cell communicators. Cell-associated sensing elements might also be involved in modulating the bacterial growth even in the presence of non-limiting (although declining) nutrient concentrations, thus promoting their economical utilisation in dense populations. Key words: quorum sensing – growth rate – autoinducer – cell density – Escherichia coli

Introduction
Acid production by incomplete oxidation of the carbon sources