How elevated pCO² modifies total and metabolically active bacterial communities in the rhizosphere of two perennial grasses grown under field conditions

The response of total (DNA-based analysis) and active (RNA-based analysis) bacterial communities to a pCO² increase under field conditions was assessed using two perennial grasses: the nitrophilic <i>Lolium perenne</i> and the oligonitrophilic <i>Molinia coerulea</i>. PCR- and reverse transcriptase-PCR denaturing gradient gel electrophoresis analysis of 16S rRNA genes generated contrasting profiles. The pCO² increase influenced mainly the active and root-associated component of the bacterial community. Bacterial groups responsive to the pCO² increase were identified by sequencing of corresponding denaturing gradient gel electrophoresis bands. About 50% of retrieved sequences were affiliated to <i>Proteobacteria</i>. Our data suggest that <i>Actinobacteria</i> in soil and Myxococcales (<i>Deltaproteobacteria</i>) in root are stimulated under elevated pCO².