Maize lines with different nitrogen use efficiency select bacterial communities with different β-glucosidase-encoding genes and glucosidase activity in the rhizosphere

We studied the molecular diversity of beta-glucosidase-encoding genes, microbial biomass, cellulase, N-acetyl-glucosaminidase, beta-glucosidase, and beta-galactosidase activities in the rhizosphere and bulk soil of two maize lines differing in nitrogen use efficiency (NUE). The maize lines had significant differences in diversity of beta-glucosidase-encoding genes in their rhizosphere, and Actinobacteria and Proteobacteria were the dominating phyla in all samples, but representatives of Bacteroidetes, Chloroflexi, Deinococcus-Thermus, Firmicutes, and Cyanobacteria were also detected. Among the Proteobacteria, beta-glucosidase genes from alpha-, beta-, and gamma-Proteobacteria were dominant in the rhizosphere of the high NUE maize line, whereas delta-Proteobacteria beta-glucosidase genes were dominant in the rhizosphere of the low NUE maize line. The high NUE maize line also showed higher glucosidase activities in the rhizosphere than the low NUE maize line. We concluded that plants with high NUE select bacterial communities in the rhizosphere differing in the diversity of beta-glucosidase-encoding genes which likely result in higher C-hydrolyzing enzyme activities. These effects on the diversity of beta-glucosidase-encoding genes may influence the C dynamics in the agro-ecosystems.