Effect of Glyphosate on Enzymatic Activities, Rhizobiaceae and Total Bacterial Communities in an Agricultural Tunisian Soil

The effect of glyphosate on richness and structure of the Rhizobiaceae and total bacterial communities in an agricultural soil after different treatments was studied. The herbicide was applied on the soil in the presence or the absence of Medicago sativa plants with or without inoculation with the Sinorhizobium meliloti reference strain RCR2011. Terminal-restriction fragment length polymorphism (T-RFLP) profiling showed that this agricultural soil has a high total microbial and rhizobial genetic diversity. To investigate the impact of the herbicide on microbial activity, fluorescein diacetate (FDA) and a panel of three enzymes (phosphatase, catalase, and protease BAA) were assessed. Depending on the type of enzyme tested, the enzymatic activities responded differently to the action of glyphosate, the presence of M. sativa, and the inoculation with RCR2011. The present work gives original insights into the effect of the herbicide on the rhizospheric area of M. sativa with or without rhizobial inoculation by the fact that glyphosate changes microbial diversity and affects soil enzymatic activities.