Dr. Karim Benzerara joined the Institute of Mineralogy and Physics of Condensed Matter (IMPMC) at CNRS and University Pierre et Marie Curie in Paris, France, in 2005, where he is currently a CNRS research scientist. His interests are in the fields of geomicrobiology, mineralogy, study of interactions between life and minerals and fossilization.
After two years of general scientific training including in Life and Earth sciences, he was admitted at l’Ecole Normale Supérieure in Paris in 1995. Following a BS and MS (1996 & 1997) in Earth Sciences there, he then prepared and succeeded the Agrégation in Life and Earth sciences which is a national competition for the recruitment of teachers. Taking advantage of this dual background in Earth and Life sciences, he obtained a PhD in Geochemistry at the Institute of Physics of the Earth in Paris (IPGP), under the supervision of Professor François Guyot. This is when he started coupling microbiology and molecular biology approaches with electron microscopy to study the terrestrial bioweathering of the Tatouine meteorite and so-called nanobacteria in Tunisia. He followed his PhD with a two year postdoctoral fellowship (one year based on a Lavoisier grant from the French Ministry of Foreign Affairs) at Stanford University, working with Professor Gordon E. Brown Jr. At this time he learnt how to use several synchrotron-based techniques including scanning transmission x-ray microscopy (STXM). He particularly benefited for that from the development by Tolek Tylisczak and David Shuh of the 11.0.2 STXM beamline at the Advanced Light Source in Berkeley on which he got a significant amount of beamtime and could develop many applications in the Earth and Environmental Science field. Karim came back to France in 2005 as a CNRS research scientist and has taught several classes in Mineralogy and Biomineralogy at University Paris Diderot, University of Orsay and Museum d’Histoire Naturelle in Paris in addition to classes in international schools . He has also been a member of the Agrégation committee since 2007 and has coadvised 6 PhD students since 2005.
Karim has been actively focusing his research on interactions between microorganisms and minerals in parallel with the search of traces left by life in the geological record throughout his early career. He has combined the study of field samples and microbe cultures in the laboratory. His reputation in the geobiology community comes partly from the fact that he was a pioneer of the use of cutting-edge analytical tools such as electron and x-ray spectromicroscopies on geomicrobiological samples, providing unprecedented views at the nanoscale of microbe-mineral interfaces. Among the punch lines of his most compelling work, including that achieved with his PhD students, one can cite:
- The demonstration of the existence of different microenvironments (redox; presence/absence of organics) at a microorganism–mineral interface and provision of unique nanometer-scale views of microbially controlled silicate weathering products.
- Evidence that microorganisms impact significantly the mineralogy of some stromatolites by producing high amounts of organic molecules associated with minerals down to the nm-scale. In parallel, evidence of high mineralogical similarities with Archean stromatolites suggesting their biogenicity as well as the existence of so-far-overlooked chemical heterogeneities of organic matter in different mineral laminations.
- Evidence that so-called nanobacteria on a meteorite and in pathological calcifications are not bacteria but minerals with implications for the search of traces of life in rocks or the identification of causes for arterial and urinary calcifications.
- Evidence for the existence of diverse biomineralization mechanisms by Fe-oxidizing bacteria leading to diverse biomineralization patterns. All provide potential traces of life that can be found in sediments or rocks.
- Finding of fossils in high-grade metamorphic rocks and evidence in these rocks for exceptional preservation of sub-microscale mineralogical and organic heterogeneities related to primary biological structures.
His work has been published in over 46 peer-reviewed articles in Geochimica et Cosmochimica Acta, EPSL, Geobiology, Geomicrobiology Journal, PNAS, Nature Geoscience, Journal of Investigative Medicine and other leading journals in Geosciences and Microbiology. He has coauthored over 90 conference presentations at the AGU, the EGU, the GSA, the Goldschmidt conference and many other meetings.
Since 2010 Karim is an associate editor of the European Journal of Mineralogy and on the Advisory Editorial Board of Geobiology. He is a member of the French Scientific Committee of the CNRS/INSU INTERVIE (interactions between life and Earth) program, of the board of directors at l’Institut de Physique du Globe de Paris and in the scientific committee of the Earth science department at the Museum d’Histoire Naturelle in Paris. He received the Bronze Medal from the CNRS in 2009, the Houtermans Medal from the European Association of Geochemistry in 2010 and a scientific subsidy from the foundation Simone et Cino Del Duca (on a proposition by members of the French Academy of Science) in 2011.
