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SUMMARY:Contributed Talk 2: Less is more: Selective advantages can explain
  the loss of biosynthetic functions in bacteria - D'Souza\, G (Max-Planck-
 Institut fr Chemische kologie)
DTSTART:20141027T150000Z
DTEND:20141027T151500Z
UID:TALK55704@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Co-authors: Silvio Waschina (Experimental Ecology and Evolutio
 n Research Group\, Department of Bioorganic Chemistry\, Max Planck Institu
 te for Chemical Ecology\, 07745 Jena\, Germany\; Research Group Theoretica
 l Systems Biology\, Friedrich Schiller University of Jena\, 07743 Jena\, G
 ermany)\, Christoph Kaleta (Research Group Theoretical Systems Biology\, F
 riedrich Schiller University of Jena\, 07743 Jena\, Germany)\, Christian K
 ost (Experimental Ecology and Evolution Research Group\, Department of Bio
 organic Chemistry\, Max Planck Institute for Chemical Ecology\, 07745 Jena
 \, Germany) \n\nBacteria that have adapted to nutrient-rich\, stable envir
 onments are typically characterized by reduced genomes. The loss of biosyn
 thetic genes frequently renders these lineages auxotroph\, hinging their s
 urvival on an environmental uptake of certain metabolites. However\, the f
 actors that govern this genome streamlining remain poorly understood. Our 
 analysis of 1532 metabolic networks revealed that auxotrophies are likely 
 to be highly prevalent in both symbiotic and free-living bacteria. To unra
 vel whether selective advantages can account for the rampant loss of anabo
 lic genes\, we systematically determined the fitness consequences that res
 ult from deleting conditionally essential biosynthetic genes from the geno
 me of Escherichia coli in the presence of the focal nutrient. Pairwise com
 petition experiments with each of 16 mutants auxotrophic for different ami
 no acids\, vitamins\, and nucleobases against the prototrophic wild type u
 nveiled a pronounced\, concentration-dependent growth advantage of around 
 13% for virtually all mutants tested. Our in silico analysis also suggests
  that bacteria are frequently auxotrophic for multiple metabolites. Also b
 acteria are frequently subjected to changes in resource environments. Henc
 e we also determined the effect of different carbon environments and epist
 asis on the fitness of Escherichia coli genotypes from whose genome one\, 
 two\, or three different amino acid biosynthesis genes have been deleted. 
 Competition experiments between auxotrophic mutants and prototrophic wild 
 type cells in one of two carbon environments revealed that plasticity and 
 epistasis strongly affected the mutants fitness individually and interacti
 vely. Taken together\, our findings suggest adaptive benefits could drive 
 the loss of conditionally essential biosynthetic genes and that both the g
 enetic background and environmental conditions determine the adaptive valu
 e of the loss of these biosynthetic functions. \n
LOCATION:Seminar Room 1\, Newton Institute
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