The effect of cowpea (Vigna unguiculata) with root mucilage on phenanthrene (PHE) dissipation and microbial community composition using phospholipid fatty acid (PLFA) analysis and artificial neural network (ANN) modeling

The objective of this study was to evaluate the effects of cowpea with root mucilage on phenanthrene (PHE) dissipation and microbial community composition. The experiment was conducted using three cowpea breeding lines (Vigna unguiculata) that differed in mucilage production. The highest PHE dissipation rate was achieved in soils planted with high root mucilage producing cowpea C1 inoculated with Bradyrhizobium, leading to 91.6% PHE disappearance in 5 weeks. Relative changes in microbial populations of different treatments were investigated by monitoring PLFA signatures. Data was analyzed by principle component analysis (PCA) and by construction of artificial neural network (ANN). Based on the PCA profiles, the ten treatments were separated into four groups. The ANN results demonstrated that fungal biomass were significantly influenced by root mucilage produced by cowpea (C1), and gram positive to gram negative bacteria ratios were shown to have a positive correlation with the presence of Phenanthrene (PHE) via a Kohonen self-organizing map (KSOM). Total PLFA biomass was significantly higher in the soil planted with cowpea line C1 inoculated with Bradyrhizobium than other treatments. Results suggest that root mucilage may contribute to the changes of the microbial biomass and composition in the rhizosphere, which in turn may positively impact PAH bioremediation. (C) 2015 Elsevier Ltd. All rights reserved.