Adaptation to nickel spiking of bacterial communities in neocaledonian soils.

Adaptation to nickel of bacterial communities of two extreme neocaledonian soils (an ultramafic soil and an acidic soil) was investigated by nickel spiking and compared with adaptation in a non-neocaledonian soil used as reference. Soil microcosms were amended with nickel chloride (NiCl2), and bacterial community structure was analysed with the ribosomal intergenic spacer analysis (RISA) technique. Then, bacterial populations that respond to nickel stress were identified by cloning and sequencing. In the ultramafic soil, a shift occurred on day zero on the assay profiles and consisted of the emergence of a bacterial group closely related to the Ralstonia/Oxalobacter/Burkholderia group. It is hypothesized that NiCl2 had a physico-chemical impact on soil structure. Fourteen days after nickel spiking, another shift occurred in the two soils that concerned a bacterial group belonging to the Actinomycete group. Only a few changes occurred in the bacterial community structure of the neocaledonian soils compared with those of the reference soil, which is more affected by nickel spiking. These results suggest that neocaledonian soil bacteria are particularly well adapted to nickel.