10-11th December 2015
ENS 29 and 45, rue d’Ulm
Salles Jaurès et Dussane
Workshop under the hospices of the CNRS-PSL Interdisciplinary Action “Domestication et fabrication du vivant”
credit photo NOAA
Speakers: Dieter Braun (LMU, Munich), Pietro Corsi (University of Oxford), René Doursat (CNRS Gif), Roland Lehoucq (CEA Saclay), Dominique Lestel (ENS, Paris), Uwe Meierhenrich (Université de Nice), Istvan Praet (Roehampton University), Yannick Rondelez (ESPCI ParisTech), Jean-Sébastien Steyer (CNRS/MNHN), John Sutherland (MRC Cambridge).
Organizing Committee: André Estevez-Torres (CNRS and Université Pierre et Marie Curie, Paris), François Guyot (Museum National d’Histoire Naturelle and Université Pierre et Marie Curie, Paris); Ludovic Jullien (Université Pierre et Marie Curie and Ecole Normale Supérieure, Paris), and Raphaël Plasson (Université d’Avignon et des Pays de Vaucluse and INRA, Avignon)
The emergence of life on Earth has long been a major field of questioning for humans. Indeed living matter has always appeared highly singular against the background of “inert” matter so as (i) to interrogate its emergence and (ii) to attempt to convey its original features to inanimate objects.
In the course of the XXth century, both latter perspectives have started to be interrogated at the cellular level with a continuously increasing content of information about the molecular components of living cells as well as about their interactions and reactivity. Two different perspectives have been adopted, focusing either on the formation of cell components, or on the onset of cell dynamic organization.
Most attempts have considered that addressing the issue of the emergence of life could reduce to reproducing the composition and organization of a living cell as we currently know them. In the corresponding picture, a living cell is mostly the assembly of its components. This perspective has generated much experimental work in the field of prebiotic chemistry, which has attempted the synthesis of (possibly homochiral) molecular modules (amino-acids, nucleotides, sugars, lipids….) integrated in the present biomolecules (proteins, nucleic acids,…) within the postulated astrophysical and planetary context of the emergence of life. In particular, these works have demonstrated that such molecular modules could be obtained and could react after appropriate activation to produce macromolecules and supramolecular assemblies exhibiting similarities with the ones presently encountered in living cells.
Another trend has considered life as an historical process, which has acted by dissipating available energy. In the corresponding picture, a living cell is an evolving network of interactions and chemical reactions. In this alternative perspective, the final goal is not anymore the present structure and composition of a living cell but the mechanism, leading from the initial state of non-living matter to the present level of biological organization. Up to the present time, most works along this perspective have been theoretical. In particular, they have emphasized on the significance of thermodynamic and kinetic considerations, bringing forward the concepts of energy dissipation, autocatalysis, replication, symbiosis, fitness, or Darwinian molecular evolution. Despite those theoretical developments, one has to admit that we still currently lack a principled, quantitative, chemically explicit theory of the requirements needed to stabilize a metabolic network and a self-generated control system far from thermodynamic equilibrium. However, emerging experimental works have benefited from the developments of analysis, imaging, high-throughput screening, microfluidics,… to bring promising results while challenging the relevance of the theoretical models.
Beyond the preceding considerations, there is a lack of fossils unambiguously expressing the activity of the very first living organisms. Moreover, claims that several core metabolic processes (e.g. reductive tricarboxylic acid cycle) would witness from the emergence of life will ever remain speculative. Hence one is also forced to recognize that the actual nature of the first organisms and the exact circumstances of the emergence of life on Earth are, at least in a large part, forever lost to science. However, this evident limitation does not prevent to recognize that life has been a successful experiment, which demonstrates what is chemically possible. Hence, more than unraveling the emergence of life, the ultimate challenge may be to construct an artificial “living” organism that could reproduce and evolve. Creating life anew should certainly help us understand how life can start as a general process, how likely it is that it exists, how diverse it might be on other worlds and, ultimately, what life is.
This colloquium will explore several aspects evoked in the preceding paragraphs:
– It will first introduce a historical perspective on questioning the emergence of life and attempting to convey life to inanimate matter. In particular, it will be shown that the corresponding challenges have considerably evolved both in their activities as well as in their motivations;
– It will then illustrate the state-of-the art of the works in communities identified as relevant to address the emergence of living systems. Beyond introducing results, particular emphasis will be put on the pictures and motivations of the researchers engaged in the field. In particular, it will be tentatively evaluated whether the existence of living biological organisms in all their present complexity should be ultimately considered as helpful to design and fabricate living systems;
– To illustrate the latter aspect, several definitions on what life is will be confronted in the light of designing and fabricating living systems. In particular, such definitions should be challenged in relation to potential applications associated to designing and constructing artificial “living” organisms that could reproduce and evolve under well-defined safety conditions, which need to be defined and will be discussed.