GEOMICROBIOLOGY OF EXTREME SOILS

International audienceOne third of New Caledonia is constituted of ultramafic rocks. The soils originating from these rocks are considered extreme since they are characterized by low organic matter and high heavy metal content. The open pit mines for nickel extraction have a significant impact on the environment by releasing heavy metals into the environment. A new mine, located on the Koniambo, north of New Caledonia, is about to be exploited. This is a unique occasion to study the impact of anthropogenic activity on the microbial diversity. The objectives of this work were to study the bacterial community diversity under the pristine conditions and to identify the soil characteristics driving the structure of bacterial communities down a Koniambo slope. Along this transect, 14 soils were sampled in triplicate and characterized for their geochemistry and bacterial diversity contents. To assess bacterial community structure, phylochips were used. The results showed that the 14 soils were clustered in 5 groups characterized by specific populations like Verrucomicrobia and Bacteroidetes for one of them and Gammaproteobacteria, Deinococcus and Crenarchaeota for another one. The microbial community structures vary in response to local characteristics such as the edaphic parameters and/or the vegetation. For example, correlations between Ca, Ni and Mg and specific populations were highlighted. In conclusion, this work emphasizes the effects of the environment on the microbial biodiversity and the dynamic underlying structure. Our improved knowledge will also help in the rehabilitation of the Koniambo site after the mining ends