Summary. Cellular metabolism consists of a complex network of chemical reactions, which transform hundreds of small molecules into each other in order to secure a reliable supply of energy and building blocks. Understanding how these networks emerged and evolved throughout the 3.8 billion years of the history of life is a fascinating and challenging endeavor, which can benefit from mathematical models and computer simulations. Relatively detailed cell-level models can help search for signatures of evolutionary adaptation in present-day organisms. Conversely, much less detailed biosphere-level approaches can help understand the adaptation of life during major evolutionary transitions, such as the oxygenation of the Earth's atmosphere, which took place about 2.2. billion years ago, or the very early stages of the emergence of life.

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(*) Dr. Daniel Segre' is Assistant Professor in the Bioinformatics Graduate Program, at the Department of Biology, and Department of Biomedical Engineering, Boston University.

He began his education at the University of Trieste, where he obtained a Physics degree in 1994. He went on to his M.Sc. at the at the Department of Molecular Genetics of the Weizmann Institute of Science, in Israel. His Life-Science Ph.D. was granted in the year 2002. His postdoctoral work during the years 2001-2004 was at the Harvard Medical School, in the Department of Genetics and Computational Biology. His present position has been held since the year 2005.

Dr. Segre has been a Visiting Scholar at the Lawrence Livermore National Laboratory, Bioscience Division. He is also Associate Editor of The Public Library of Science Computational Biology, a publication that features works of exceptional significance for our further understanding of living systems at all scales-from molecules and cells to ecosystems-through the application of computational methods.

His remarkable early research in astrobiology, namely on the Lipid World, was done at Weizmann in collaboration with Professor Doron Lancet. Some of this work has already been presented at the Trieste Conferences of Astrobiology that were held at the ICTP.

His more recent publications about which we shall learn at the seminar include "The effect of oxygen on biochemical networks and the evolution of complex life" that was published in Science a year ago, together with related material published in Nature Genetics, a year earlier.