Editors' Introduction to Special Issue Ute Deichmann, Michel Morange, and Anthony S. Travis In this second decade of the 21st century, we find the pervasive influence of synthetic biology everywhere, not only in research laboratories, but also in the discourses of politicians and ethicists. Despite its ubiquity, the precise meaning of the notions of "synthetic biology" and "synthetic life," as well as their history, potential, and risks, remain obscure not only to the layperson, but also to most biologists. The aim of this special issue is twofold. First, it is intended to help the reader better appreciate what synthetic biology is all about and what are its roots. Second, once the overall picture has been expounded and made clearer, the questions of whether research in synthetic biology raises new and specific ethical issues, and how to control the experiments in this field, can be based on a firmer ground. François Jacob argued that the best way to know what molecular biology really is, is to look at what molecular biologists do in their laboratories. We have adopted the same strategy here. Therefore, the first three contributions describe different and complementary aspects of research pursued in synthetic biology. It is naturally proper to commence this overview with the experiment that has had the most obvious media impact: the production by CraigVenter's group of a bacterial cell with a chemically synthesized genome. John Glass, who was closely associated with the project from its beginnings, describes not only the obstacles that had to be overcome to reach this outcome, but also underlines the fact that the experiment consists of two different steps, each endowed with its own difficulties: the chemical synthesis of a full-length genome, and its transplantation into a recipient bacterium. This successful experiment is as much a beginning as it is an achievement: it opens the possibility of constructing the minimal genome compatible with life, and through this of casting new light on the nature of life. This top-down approach to a definition of life is complemented by other bottom-up work done in synthetic biology, aiming at progressively introducing in simple physicochemical systems what is required to generate "living systems." [End Page 470] Wilfried Weber and his colleagues describe another dimension of synthetic biology, its ambition to engineer (program) cells for biological and biomedical applications. The latter can be highly diverse, from mimicking host-parasite interactions to efficiently screening new drugs against tuberculosis. Gregory Linshiz and his colleagues go a step further and suggest that the development of synthetic biology is nothing less than a scientific revolution. It requires the fusion of biology with computer science and engineering, a new breed of scientists, the construction of a new language of communication, and a new division of labor. Linshiz's contribution also points to the second strategy that we have used to determine what synthetic biology is: we positioned it in the historical development of biological knowledge, in order to appreciate its true novelty. This approach shows that reflections and research on the synthesis of life in the laboratory are much older and broader in scope than the extant synthetic biology. Ute Deichmann reminds us that the refutation at the end of the 19th century of the spontaneous generation of life, and of crystallizing cells from inanimate matter, by Pasteur, Remak, and Virchow, to mention only the most prominent researchers, was a prerequisite for the start of numerous projects targeted at synthesizing life. These projects were guided by very different central conceptions, such as growth and form on the one hand, and specificity of organisms' molecules and reactions on the other. However, Deichmann does not support relativistic views, showing that though morphological-mathematical approaches succeeded to mimic certain properties of life, the underlying conceptions turned out not to be fruitful. All extant projects are based on the specificity of macromolecules as the basis of life. To understand what exactly synthetic biology is also requires an exposition of what, clearly, it is not. Michel Morange shows that the recurrent discourse among some synthetic biologists who claim that they will improve the functions of organisms and do what evolution was unable to accomplish does not correspond to reality. Further...
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