Comptes Rendus Biologies最新文献

Cell division is fundamental for living organisms, sustaining their growth and development. During cell division a single mother cell will duplicate its genome and organelles, and give rise to two independent entities that will eventually split apart in a tightly regulated process called abscission or the final-cut. In multicellular organisms, newly born daughter cells split apart while they simultaneously need to maintain contact for intercellular communication. In this mini-review, I discuss this fascinating paradox of how cells across kingdoms combine the need to divide with the need to connect.

Microalgae are prominent aquatic organisms, responsible for about half of the photosynthetic activity on Earth. Over the past two decades, breakthroughs in genomics and ecosystem biology, as well as the development of genetic resources in model species, have redrawn the boundaries of our knowledge on the relevance of these microbes in global ecosystems. However, considering their vast biodiversity and complex evolutionary history, our comprehension of algal biology remains limited. As algae rely on light, both as their main source of energy and for information about their environment, we focus here on photosynthesis, photoperception, and chloroplast biogenesis in the green alga Chlamydomonas reinhardtii and marine diatoms. We describe how the studies of light-driven processes are key to assessing functional biodiversity in evolutionary distant microalgae. We also emphasize that integration of laboratory and environmental studies, and dialogues between different scientific communities are both timely and essential to understand the life of phototrophs in complex ecosystems and to properly assess the consequences of environmental changes on aquatic environments globally.

I attempt in this essay to shed new light on the origins of Louis Pasteur's uniquely progressive mind and spirit and the various factors in his background and upbringing that shaped them. There is, however, very limited documentation on the early period of Pasteur's life, apart from his son-in-law's (René Vallery-Radot) biographical account, and this is considered by many as more akin to a work of hagiography. We do have, on the other hand, Pasteur's correspondence with his parents and sisters as compiled and annotated by his grandson, Louis Pasteur Vallery-Radot. Using these limited sources, combined with what we know about Pasteur's home environment and early education, his cultural influences (like the books he read), and his drawings and etchings, I have attempted in this essay to hypothesize regarding the influences during Pasteur's childhood, adolescence, and very early adult years as a scientist and how they contributed to the formation of Pasteur's mind and spirit, while fully acknowledging the extent to which this is based on indirect evidence and, occasionally, outright speculation.

In the 19th century, the applications of the scientific discoveries of Louis Pasteur to medicine had difficulty in imposing themselves within the French medical community and its National Academy. Among those concerning infectious diseases, their prevention by hygiene and their etiology by microbes are described here. Louis Pasteur found it difficult to convince and had to fight, to show through the surgical practice of asepsis and examples of infections induced in animal models (anthrax), the modes of transmission of germs and their pathogenicity.

Pasteur's originality in the way he developed pure research is to have understood the importance, for society, of the underlying motivation. Curiosity, of course, is a strong motivation, which explains why we seek to understand the origin of life. But, in front of the immensity of the possible choices, why not, also, choose to start from questions of economic interest (diseases of beer and wine, diseases affecting the silk industry ...) Finally, of course, health is a constant preoccupation, but the diseases, which have no borders, often come from tropical countries and Asia especially. It is therefore necessary to settle there, but not to come and impose one's point of view, but on the contrary to use the knowledge coming from the local culture in order to open new ways of understanding the reality of the world.

Louis Pasteur is celebrated as the founding father of microbiology. But he was a chemist by training and discovered molecular dissymmetry experimentally. All his life, his constant preoccupation will be to apply the method and strategies of the fundamental sciences to living processes, "from the molecule to the brain". His fundamental aim will be, beyond the biology of microbes, the chemistry of life, a disposition which signs the originality of his work. More unexpectedly, Pasteur was at the origin of therapeutic chemistry-which his successors, and especially Daniel Bovet, brilliantly illustrated at the Pasteur Institute and which they would pursue with the pharmacology of the nervous system or "neuropharmacology".

Pasteur's work on fermentations has variously influenced the conception that veterinarians had of the origin of virulent diseases. Jean-Baptiste Chauveau asserted as early as 1866 the specificity of contagious diseases and their exogenous origin. Henri Bouley was initially a supporter of the spontaneity of these diseases. He became an advocate of the germ theory when Pasteur unambiguously demonstrated the causal role of anthrax bacteridia in 1877. Pasteur then had a fruitful collaboration with veterinarians during his work on chicken cholera, swine erysipelas, contagious pleuropneumonia and rabies. After Pasteur's experience at Pouilly-le-Fort, Henri Bouley and Edmond Nocard, a disciple of Pasteur, were strong advocates for the adoption of vaccinations by veterinarians and farmers. Nocard's work on various contagious animal diseases greatly contributed to the foundation of veterinary microbiology.

From 1865 to 1869, on a "government order", Louis Pasteur tackled a silkworm disease, the pebrine, which was ruining the economy of southern France. Well beyond the scientific results-he was going to highlight a second disease, the flacherie-and the operational results-he installed techniques to limit the progression of one disease and protected the farms from the other-, this sequence opened the door to what would become Pasteur's working method: a science involved in practice, a great importance given to the team of collaborators and to innovations of all kinds, in this case, microphotography. It also establishes the characteristics of the socialization of the Pasteurian approach: diffusion of methods among all the social actors concerned, networking of scientists and internationalization of research.