Francois Jacob studied in bacteria and bacteriophages at the Institut Pasteur in Paris, France, in the second half of the twentieth century. In 1965, Jacob won the Nobel Prize in Physiology or Medicine with Andre M. Lwoff and Jacques L. Monod for their work on the genetic control of enzyme synthesis. Jacob studied how genes control and regulate metabolic enzymes in the bacterium Escherichia coli (E. coli) and in lysogenic bacterial systems. He contributed to theories of transcriptional gene regulation, the operon model, and the distinction between structural and regulatory genes. Jacob also introduced the concept of bricolage (tinkering) in evolutionary biology.
In his essay Evolution and Tinkering, published in Science in 1977, Francois Jacob argued that a common analogy between the process of evolution by natural selection and the methods of engineering is problematic. Instead, he proposed to describe the process of evolution with the concept of bricolage (tinkering). In this essay, Jacob did not deny the importance of the mechanism of natural selection in shaping complex adaptations. Instead, he maintained that the cumulative effects of history on the evolution of life, made evident by molecular data, provides an alternative account of the patterns depicting the history of life on earth. Jacob's essay contributed to genetic research in the late twentieth century that emphasized certain types of topics in evolutionary and developmental biology, such as genetic regulation, gene duplication events, and the genetic program of embryonic development. It also proposed why, in future research, biologists should expect to discover an underlying similarity in the molecular structure of genomes, and that they should expect to find many imperfections in evolutionary history despite the influence of natural selection.
Lysogenic bacteria, or virus-infected bacteria, were the primary experimental models used by scientists working in the laboratories of the Pasteur Institute in Paris, France, during the 1950s and 1960s. Historians of science have noted that the use of lysogenic bacteria as a model in microbiological research influenced the scientific achievements of the Pasteur Institute's scientists. Francois Jacob and Jacques Monod used lysogenic bacteria to develop their operon model of gene regulation, to investigate the cellular regulatory mechanisms of the lysogenic life cycle, and to infer the process of cellular differentiation in the development of more complex eukaryotes.