title: Bacterial Unculturability and the Formation of Intercellular Metabolic Networks.
abstract: The majority of known bacterial species cannot be cultivated under laboratory conditions. Here we argue that the adaptive emergence of obligate metabolic interactions in natural bacterial communities can explain this pattern. Bacteria commonly release metabolites into the external environment. Accumulating pools of extracellular metabolites create an ecological niche that benefits auxotrophic mutants, which have lost the ability to autonomously produce the corresponding metabolites. In addition to a diffusion-based metabolite transfer, auxotrophic cells can use contact-dependent means to obtain nutrients from other co-occurring cells. Spatial colocalisation and a continuous coevolution further increase the nutritional dependency and optimise fluxes through combined metabolic networks. Thus, bacteria likely function as networks of interacting cells that reciprocally exchange nutrients and biochemical functions rather than as physiologically autonomous units.
authors.affiliation: Experimental Ecology and Evolution Group, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany; Current address: Evolutionary Biology Group, Institute for Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland. Electronic address: samayrp@gmail.com.
authors.forename: Samay
authors.initials: S
authors.lastname: Pande
authors.affiliation: Experimental Ecology and Evolution Group, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany; Current address: Department of Ecology, School of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany. Electronic address: christiankost@gmail.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Kost
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism*; D001431:Bacteriological Techniques; D001692:Biological Transport; D004926:Escherichia coli / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D059013:Microbial Consortia / Q000502:physiology*; D043942:Nanotubes; D064210:Secondary Metabolism
keywords: adaptive gene loss; metabolic cross-feeding; metabolic trade-off; positive assortment; privatization; unculturability