Natural soil was collected in the Marseille area.No specific permissions were required for these
activities; field studies did not involve endangered or protected
species. The soil sample was analysed for granulometry, mineral and
biological composition (LCA Laboratories). The results were repeated
and validated according to the accreditation of the laboratory (Table
1). Soil was then steam-sterilized and further humidified by adding
2 ml sterile distilled water per 50 g sterilized soil.