Detlev W. Bronk Professor
Our research centers on questions concerning the origin of life.
With Dieter Braun we focused on physics questions, i.e., the effect of temperature gradient present in thermal vents along tectonic plates. We showed that thermophoresis and thermal convection can help to sustain very high concentrations of DNA or proteins so that we don't have the nagging question of reaching a critical concentration for the early soup chemical reactions. We also showed that DNA sequences can be replicated very fast by a natural polymerase chain reaction. The conclusion is that non-equilibrium processes must have played an important role in early life forms.
Reference: Thermal Force Approach to Molecular Evolution, by Dieter Braun and Albert Libchaber. Phys. Biol. 1, P1-P8 (2004).
In a more mechanical approach to early life, Vincent Noireaux is approaching the minimal conditions to produce an artificial cell. To start, a cell free extract is encapsulated into a phospholipid vesicle which includes also the necessary genes and their simple regulation (phage regulation). A pore is expressed inside the vesicle, transforming the membrane in a dialysis compartment, where ATP, nucleotides and amino-acids can easily exchange between the extract inside and a feeding solution outside, all the proteins staying inside the vesicle. From thereon, Vincent is trying to produce an active membrane, using relevant genes.
In a more chemical approach, Jean Lehmann is trying to study possible elementary life forms when mainly four amino-acids were present, a model given for early life. The 4 amino-acids Valine, Alanine, Glycine, Aspartate correspond to the 4 codons, GUC, GCC, GGC, GAC. They represent more than 95% of the amino-acids produced in the classical experiment of Miller and Urey. One of Jean's hypotheses is that non-enzymatic processes are possible in this simplified molecular world to produce polypeptides.
In a different context, Hanna Salman studies how a bacteria colony responds to an abrupt change in the environment. In his case, he changes the nourishing carbon source from glucose to lactose. The study is done following many generations to reach a steady state. The bacteria are thus growing in a chemostat and studied for up to 50 generations. On this time scale the adaptive dynamics seem to differ from the short time scale where the Lactose operon is turned on.