In recent years, the field of molecular biology has moved away from the study of individual components and toward the study of how they interact, creating a “systemic” approach that seeks an appropriate and quantitative description of cells and organisms. Dr. Leibler’s laboratory is developing both the theoretical and experimental methods necessary for conducting studies on the collective behavior of biomolecules, cells and organisms. By selecting a number of basic questions on how simple genetic and biochemical networks function in bacteria, his lab is beginning to understand how individual components can give rise to complex, collective phenomena.

The first signaling system the laboratory chose to study is the bacterial chemotaxis network. Through both quantitative analysis of bacterial behavior and modifications of the intracellular biochemistry, they elucidated several basic properties of the network, namely the network’s robustness and sensitivity to biochemical modifications of its components. By observing the behavior of individual bacteria while measuring the concentrations of the different components of the chemotaxis network, the lab was also able to examine how nongenetic individuality, the large variations in the behavior of genetically identical bacteria, is established.

Dr. Leibler’s lab has also examined the resistance of genetic networks to noise, such as the noise connected with fluctuations in the number of the network’s different components. Using the genetic circuit underlying the circadian clock in cyanobacteria, the laboratory has examined both the physical and biochemical basis by which this noise is absorbed. The laboratory is also interested in building similar networks, such as clocks or logical gates, artificially, using natural components, in order to better understand their functioning and evolvability.

More recent research topics in the laboratory include quantitative studies of interacting microorganisms. In particular, the question of the survival of microbial populations in varying environments is being addressed both experimentally and theoretically. Dr. Leibler and his collaborators are interested in developing new technologies that will facilitate the process of moving from the component descriptions to system descriptions, and they are working on developing mathematical and physical tools that will aid in the extraction of information about different biological networks based on analyzing the interactions between their components under different conditions.

CAREER

Dr. Leibler did his undergraduate studies in physics at the University of Warsaw. In 1979, he finished his M.S. in theoretical physics from the University of Paris, going on to a Ph.D. in 1981, and a second Ph.D., also from the University of Paris, in 1984 in physics. After a year at the École Normale Supérieure, he became a tenured research fellow at the Centre d’Études de Saclay in 1984, staying until 1992. Dr. Leibler was also a visiting research associate at Cornell University from 1985 to 1987, and a visiting professor at the École Supérieure de Physique et Chimie Industrielles in Paris, France. Dr. Leibler moved to Princeton University in 1992 as a professor in the department of physics, becoming a professor in the department of molecular biology in 1993. He spent the year from 1997 to 1998 as a visiting scientist at the European Molecular Biological Laboratories, in Heidelberg, Germany. During his last year at Princeton, from 2000 to 2001, Dr. Leibler was a Howard Hughes Medical Institute investigator. He moved to Rockefeller University in 2001, becoming a Tri- Institutional professor at Weill Medical College of Cornell University and the Sloan-Kettering Institute for Cancer Research in 2003.