title: In silico evolution of diauxic growth.
abstract: BACKGROUND
  The glucose effect is a well known phenomenon whereby cells, when presented with two different nutrients, show a diauxic growth pattern, i.e. an episode of exponential growth followed by a lag phase of reduced growth followed by a second phase of exponential growth. Diauxic growth is usually thought of as a an adaptation to maximise biomass production in an environment offering two or more carbon sources. While diauxic growth has been studied widely both experimentally and theoretically, the hypothesis that diauxic growth is a strategy to increase overall growth has remained an unconfirmed conjecture.
  
  
  METHODS
  Here, we present a minimal mathematical model of a bacterial nutrient uptake system and metabolism. We subject this model to artificial evolution to test under which conditions diauxic growth evolves.
  
  
  RESULTS
  As a result, we find that, indeed, sequential uptake of nutrients emerges if there is competition for nutrients and the metabolism/uptake system is capacity limited.
  
  
  CONCLUSIONS
  However, we also find that diauxic growth is a secondary effect of this system and that the speed-up of nutrient uptake is a much larger effect. Notably, this speed-up of nutrient uptake coincides with an overall reduction of efficiency.
  
  
  CONCLUSIONS
  Our two main conclusions are: (i) Cells competing for the same nutrients evolve rapid but inefficient growth dynamics. (ii) In the deterministic models we use here no substantial lag-phase evolves. This suggests that the lag-phase is a consequence of stochastic gene expression.
authors.affiliation: School of Computing, University of Kent, Canterbury, CT2 7NF, UK. D.F.Chu@kent.ac.uk.
authors.forename: Dominique F
authors.initials: DF
authors.lastname: Chu
mesh_terms: D019020:Directed Molecular Evolution; D004926:Escherichia coli / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D056084:Genetic Fitness; D005947:Glucose / Q000378:metabolism; D008954:Models, Biological
chemical_list: D005947:Glucose