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Laboratory of Living Matter

Stanislas Leibler
Gladys T. Perkin Professor

Analysis of Biological Networks

In recent years molecular biology has moved away from the study of individual components towards the study of many interacting components. The "systemic" approach seeks an appropriate, and if possible, quantitative description of cells and organisms. Both the theoretical and experimental methods necessary for such studies still need to be developed. We are far from understanding even the simplest collective behavior of biomolecules, cells or organisms.

We try to tackle some basic questions connected with the functioning and evolution of simple genetic and biochemical networks. Some problems studied recently both experimentally and theoretically in our laboratory are:

  • Robustness and sensitivity of networks with respect to biochemical modifications of their components. This problem was addressed for the chemotaxis network in Escherichia coli, where robustness of adaptation and "non-genetic individuality" in cellular responses coexist.
  • Resistance of genetic networks to molecular noise, such as the noise connected with fluctuations in the number of different components. For this we studied genetic networks such as the circadian clock in cyanobacteria. The problem of stochastic behavior on the cellular level was approached in the study of the switching of flagellar bacterial motors.
  • Precision and establishment of proportions (scaling) in spatial pattern formation. This problem was addressed in a quantitative experimental study of the early Drosophila development, where for the anterior-posterior axis both precision and scaling seem to appear in the very first steps of the genetic pattern formation cascade.
  • Design and construction of simple artificial networks with a desired functionality. We constructed and studied simple genetic networks in bacteria, which function as clocks, logical gates, etc.

We hope to continue similar studies in different model organisms, with a much heavier emphasis on connected evolutionary aspects.