In memoriam Piotr Slonimski (1922-2009) the unconventional yeast geneticist.

PIOTR Slonimski, one of the forebears of yeast molecular genetics, died in Paris, France April 25, 2009. He was 86 years old. His exceptional personality and scientific contributions made him so well known among the international genetic community that his first name, Piotr, was usually sufficient to identify him in conversation. During the early 1970s, Slonimski was one of the principal founders of mitochondrial genetics, and for many years had a considerable impact on this field of research. In the last two decades, he became a prominent advocate for genomics and published original work in this field until just two months before his death. To those who believe that efficiency in science necessitates carefully planned projects, a hierarchical organization, and clear, short-term objectives, the successful career of Slonimski illustrates the opposite. His continuous scientific activity over 62 years demonstrates that intellectual curiosity, imagination, intuition, and a unconventional touch combine to form recipes for discoveries, if applied with scientific rigor and tenacity. His major legacy to the many students he has trained is to concentrate on unexpected results and, when faced with the choice between a plausible hypothesis and a more original one, to always favor the latter. Slonimski was born in Warsaw, Poland on November 9, 1922. He studied medicine in clandestinity during the Second World War and, according to his own accounts, discovered genetics by accident when, engaged in an act of sabotage of the Polish inner army, he found a German book among the ruins of a police station. The book briefly mentioned the recent transplantation experiments performed on Drosophila larvae by the American scientist George Beadle and the Russian-born French scientist Boris Ephrussi. Their results indicated how genes, whose molecular nature was unknown at the time, determine the phenotype of the transplanted eyes through a combination of intermediate substances, yet also of unknown nature. In 1947, having obtained his medical doctorate from the University Jagellone in Krakow, Poland, Slonimski arrived in Paris and knocked at the door of the laboratory of Boris Ephrussi at the Institut de Biologie Physico-Chimique. Soon afterward, he embarked on the study of the nature and the role of genes. This laboratory had just discovered the petite mutants of the yeast Saccharomyces cerevisiae. Those mutants were unconventional in many aspects. They did not follow the Mendelian rules of inheritance of nuclear genes that were, by then, solidly established. Instead, the petite mutants suggested the existence of a novel source of inheritance, located in the cytoplasm. With the help of a fellowship from Centre National de la Recherche Scientifique (CNRS), Piotr Slonimski demonstrated that this novel source of inheritance was necessary for the formation of respiratory enzymes and obtained his Ph.D. in 1952. ‘‘Cytoplasmic inheritance,’’ as it was then called in genetics textbooks, was in fact a conglomerate of very different phenomena, as we now know. But at the time, as Boris Ephrussi once joked, there were two kinds of inheritance: nuclear inheritance and unclear inheritance. Piotr Slonimski naturally opted to study the second one. And so, a few years later, mitochondrial genetics was born. By that time, DNA was identified as the genetic material, and in the 1950s CNRS decided to group the French laboratories of genetics in modern buildings constructed on the woody slopes of the Vallée de Chevreuse in Gif-sur-Yvette, southwest of Paris. The discovery by Slonimski and his collaborators’ discovery that petite mutants resulted from extensive alteration of their mitochondrial DNA opened the route to the study of this novel genome. A few years later, as research accelerated, CNRS built the Centre de Génétique Moléculaire in Gif-sur-Yvette, a larger and more modern research facility that Piotr Slonimski directed from 1971 to 1991. With