Résumé
The response of total and active bacterial communities to a pCO sub(2) increase under field conditions using two perennial grasses namely, the nitrophilic Lolium perenne and the oligonitrophilic Molinia coerulea, was assessed. Sampling was performed at three sampling dates on 21 June, 7 May 2002, and 15 July 2002. Sampling of L. perenne was always performed just before a cut. Two fractions were recovered namely, the non-adhering soil and the root itself. DNA extraction and purification were performed on about 0.5 g of fresh root or soil material. Bacterial groups responsive to the pCO sub(2) increase were identified by sequencing of corresponding denaturing gradient gel electrophoresis bands. It was observed that the changes induced by high pCO sub(2) were more pronounced on active than on total communities at root vicinity.