L' Annee biologique最新文献

The actual technological revolution is largely sustained by developments in biotechnology. The rapid acquisition of knowledge in biological sciences, coupled with the advancement in robotics and computer sciences and with the multiplication of bio-industries, have caused a worldwide disruption of socio-economical conditions. Some remarks on these consequences are emphasized here, with respect to agribusiness, health and the environment. Agriculture now depends on upstream related industries and food producers are under increasing pressure from food transformers and distributors. In this situation, genetically modified organisms are introduced on the market. Both their advantages (e.g., extensive production, enlargement of the distribution areas of species, lowering the use of pesticides, synthesis of micronutrients and pharmaceutical essences, materials for interspecies transplant) and risks (e.g., deepening of the N-S rupture, settlement of farming, health and environment hazards) are stressed. In the health field biotechnologies are involved in the research for the improvement of fitness and lifetime primarily for those living in rich countries, in the increasing cost of public health care, in the situation of senior citizens. Biotechnologies are also at the basis of health problems (listeriose, diseases due to animal feeding diet). In the environmental field, challenges are the increasing shortage of water resources, pollutions of different nature, and the global warming of the earth. At the entry of the xxi century, will biotechnologies allow the development of small farms, with the agricultural practice based on science of “functional food”? Does the knowledge of genome expressions and the development of proteomic analyses allow the prediction and the prevention of genetic diseases and certain forms of cancer? Does the discovery of new vaccines allow the eradication of parasitoses such as flu, AIDS, malaria and various incoming viral diseases? In the genome therapy will conclusive recovery be achieved? All these results could be obtained in the context of the need for an universal health right and an appropriate control of health cost? Will biotechnologies help discover the sources of pollutions and facilitate their eradication and decontamination? Will their applications in energetic industries (biofuels, biogases) become profitable? Will the necessary regulation of the conditions of the new markets meet success? The granting of patents is one of the difficulties to deal with. Will the oligarchic powers of the economical actors be able to keep in balance with the political powers? In democracy, all citizens have to participate in the decisions concerning their way of life. Are they interested? Is it possible to democratically regulate the controlable effects of biotechnologies? These are the questions which are to be dealt with in this paper.

Tcslate amoeba are a heterogeneous and most likely polyphyletic group of free-living protists. Their common characteristic is the presence of a test. Testate amoebae have been observed in almost every aqualic habitat, mainly in the periphytic zone of fresh and salt water bodies, soils and mosses. These protozoa are of great interest in the study of ecosystems. Indeed, the presence of a rigid test makes their identification relatively easy and they are good biological indicators. Furthermore, these micro-organisms play a key role in the structure and the functioning of microbial communities at the surface of Sphagnum peatlands. Nevertheless, testate amoebae remain globally little studied. More precisely, only limited data exist on their feeding habits although this is a necessary preliminary key aspect to understand their role in microbiai trophic networks. The aim of this review therefore is to allow a synthesis of the observations at hand in the literature on the feeding behaviour of testate amoebae. An important part of this review is devoted to our own observations on the species living in Sphagnum. Although testate amoebae arc generally believed to be heterotrophic. several species arc mixotrophic. Strict heterotrophy however remains the dominant trophic mode of testate amoebae. In the literature, several authors consider testate amoebae as largely bacterivorous. It seems however that many species ingest other kinds of prey: paniculate organic matter, microalgae, plant cells, prolists, fungi and small metazoa. Furthermore, some species are polyphagous while others seem to have more specialised feeding habits. Little is known on prey identification by testate amoebae. In particular, it is difficult to tell if mechanisms of distant detection (e.g. chimiotactism) exist or if a physical contact is necessary. Our observations on living and on fixed individuals suggest that both mechanisms exist. Furthermore, it seems that the food selectivity by testate amoebae is influenced by the physiological state of prey organisms at the moment of their ingestion. As for naked amoebae, the ingestion of prey is done by invagination of the cytoplasmic membrane. However, the particularity of testate amoebae is that the ingestion and egestion lake place at the level of the pseudostome. but no clearly defined cytostome or cytoprocte exist. The ability of some testate amoebae species to ingest a wide range of prey sizes (0,2 to 1 000 μm) and of very different kinds likely represents an competitive advantage in some environments. In these conditions, it seems important to improve our knowledge on the biology and the ecology of these protozoa.