Co-Inoculation Am Fungi And Rhizobia Stimulate Atrazine Dissipation Via Profiling Atrazine-Degrading Bacteria Community at the Aggregate Scale

Abstract

As a potential low-cost and environmentally friendly approach, bioremediation of herbicide contaminated soil has attracted increasing attention. It is well known that arbuscular mycorrhizal (AM) fungus Glomus mosseae increases atrazine dissipation in soil, and rhizobia Rhizobium trifolii TA-1 is considered as an excellent solubility enhancer for atrazine. However, there was a lack of the knowledge about underlying mechanism of co-inoculation AM fungi and rhizobia on atrazine dissipation, particularly the responses of atrazine-degrading bacteria community at the aggregate scale. In this study, a pot experiment in greenhouse was conducted respectively with G. mosseae (AM), R. trifolii TA-1 (R) and their co-inoculation (AMR) with atrazine addition. In each treatment, soil samples were collected and divided into four soil size aggregates, including large macroaggregates (>2mm, LMa), small macroaggregates (0.25-2 mm, SMa), microaggregates (0.053-025 mm, Mia) and primary particles (<0.053 mm, P) to investigate atrazine-degrading bacteria community. The results showed that atrazine residue was lowest in AMR, and that in LMa was also significantly lower than other smaller aggregate sizes. Totally inoculation, aggregate fraction and their interaction had significant effect on soil TN, SOC, AP and pH. For atrazine-degrading bacteria community, Chao1 index of increased with decreasing particle size, yet the Shannon index decreased. Meanwhile, abundances of dominant atrazine-degrading bacteria genera Arthrobacter, Bacillus, Marmoricola and Nocardioides in the Mia and P particle size were both higher than that in the LMa and SMa of each treatment. The bacterial community in the Mia and P particle sizes was more complex of each treatment. Therefore, co-inoculation AM fungi and rhizobia stimulated atrazine dissipation by changing atrazine-degrading bacteria community, and the response of atrazine-degrading bacteria community in each aggregate size is various depending on its distinct soil physicochemical property and aggregate pore characteristics.

Keywords: Glomus mosseae, Rhizobium trifolii TA-1, Herbicide dissipation, Soil aggregates, Atrazine-degrading bacteria