Diatoms’ animal side revealed ------------------------------------------------------------------------------------------------------------------------ Found in every aquatic environment, diatoms are a major component of phytoplankton, and play an active role in producing the chemical compounds that are essential for life. Photosynthesis by these unicellular microalgae generates as much as a fifth of the oxygen we breathe. By studying one of these species more closely, biologists have shown that diatoms use the urea cycle to efficiently metabolize the carbon and nitrogen present in their environment. Until now, it was thought that the urea biochemical pathway first appeared with the metazoans, which include all animals. This unexpected finding completely changes the position assigned to diatoms in the classification of living creatures. It suggests that the evolution of these aquatic organisms followed a fundamentally different route from that of the plants and green algae to which they are related. It would appear that before acquiring the ability to photosynthesize, the ancestors of diatoms were much closer to animals than to plants. Nature May 2011 Diatoms collected in the Patagonian Channels. The disappearance of paternal mitochondria finally explained In most organisms, the mitochondrial DNA carried by sperm cells beamline at the SOLEIL synchrotron facility, which was used to mimicThe circularly polarized ultraviolet (UV-CPL) beam on the DESIRS is not transmitted to the offspring. By using a nematode worm as the conditions encountered in some space environments. a model organism, researchers have identified the mechanism by which the egg ‘digests’ the paternal mitochondria a few minutes The asymmetry of biological molecules after fertilization. Other research carried out on mice indicates that may have come from space this mechanism operates in a similar way in mammals. In the future, this work could help to improve animal cloning techniques and Just like our hands, some molecules can exist in two symmetrical medically assisted reproduction. structural forms. However, on Earth, biological molecules are only found in one form, either left- or right-handed. By synthesizing amino Science October 2011 acids in conditions simulating interstellar space, astrophysicists have succeeded in obtaining a mixture containing a significant excess of molecules of only one form. The experiment lends weight to the hypothesis of a cosmic origin for the structural asymmetry of terrestrial biological molecules. Probing hydrothermal vents to pierce The Astrophysical Journal Letters January 2011 the secrets of life’s origins Off the Azores, at a depth of 1,700 meters, the Lucky Strike hydrothermal vent field, a genuine sea-floor laboratory, is being scrutinized by the instruments of the MoMarsat mission. The sampling and physico-chemical measurements continuously carried out during Mathematical models used to reconstruct the latest campaign will help to detect the signs of past microbial activity in the rocks of the oceanic crust. One of the main challenges past biodiversity are often contradicted by is to understand how life develops in deep-sea hydrothermal vent fossil data collected in the field. A model ecosystems deprived of any solar energy. developed by a team of biomathematicians provides an explanation for these MoMarsat Campaign 28 June- 23 july 2011 inconsistencies and makes it possible to correct them. -------------------------------------- 17 2011 A year at CNRS
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