Prevalence of Deltaproteobacterial sequences in gene pools associated with the rhizosphere of native switchgrass from Tall Grass Prairie (Oklahoma, USA).

The potential nitrogen-fixing bacterial diversity in the rhizospheric soil of the native switchgrass ( L.) from Tall Grass Prairies of Northern Oklahoma was studied using a partial region of nitrogenase structural gene-. Eleven clone libraries constructed from amplicons gave 407 good-quality sequences. More than 70% of sequences showed similarity of with uncultured bacteria (< 98%). The dominance of sequences affiliated with Deltaproteobacterial was observed, followed by Betaproteobacterial sequences. The gene library was dominated by the genera and . Sequences affiliated with rhizobia, such as , etc., were also in the rhizosphere in small numbers. From Deltaproteobacteria, five genera, namely , , , , and contributed to 48% of the total sequences suggesting the dominance of group Deltaproteobacteria in the rhizosphere of native switchgrass. Considering the percent similarity of the sequences with cultivated bacteria, this study demonstrated the presence of novel bacterial species in switchgrass rhizospheric soil from Tall Grass Prairie.