title: Effects of cowpea (Vigna unguiculata) root mucilage on microbial community response and capacity for phenanthrene remediation.
abstract: Biodegradation of polycyclic aromatic hydrocarbons (PAHs) is normally limited by their low solubility and poor bioavailability. Prior research suggests that biosurfactants are synthesized as intermediates during the production of mucilage at the root tip. To date the effects of mucilage on PAH degradation and microbial community response have not been directly examined. To address this question, our research compared 3 cowpea breeding lines (Vigna unguiculata) that differed in mucilage production for their effects on phenanthrene (PHE) degradation in soil. The High Performance Liquid Chromatography results indicated that the highest PHE degradation rate was achieved in soils planted with mucilage producing cowpea line C1, inoculated with Bradyrhizobium, leading to 91.6% PHE disappearance in 5 weeks. In root printing tests, strings treated with mucilage and bacteria produced larger clearing zones than those produced on mucilage treated strings with no bacteria or bacteria inoculated strings. Experiments with 14C-PHE and purified mucilage in soil slurry confirmed that the root mucilage significantly enhanced PHE mineralization (82.7%), which is 12% more than the control treatment without mucilage. The profiles of the PHE degraders generated by Denaturing gradient gel electrophoresis suggested that cowpea C1, producing a high amount of root mucilage, selectively enriched the PHE degrading bacteria population in rhizosphere. These findings indicate that root mucilage may play a significant role in enhancing PHE degradation and suggests that differences in mucilage production may be an important criterion for selection of the best plant species for use in phytoremediation of PAH contaminated soils.
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail: xiaxue8005@gmail.com. Electronic address: xiaxue8005@gmail.com.
authors.forename: Ran
authors.initials: R
authors.lastname: Sun
authors.affiliation: Department of Environmental Sciences, University of California at Riverside, Riverside, CA 92521, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Belcher
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail: xiaxue8005@gmail.com.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail: xiaxue8005@gmail.com.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Environmental Sciences, University of California at Riverside, Riverside, CA 92521, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Thater
authors.affiliation: Department of Environmental Sciences, University of California at Riverside, Riverside, CA 92521, USA. Electronic address: Crowley@ucr.edu.
authors.forename: David E
authors.initials: DE
authors.lastname: Crowley
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail: xiaxue8005@gmail.com. Electronic address: weigehong@nwsuaf.edu.cn.
authors.forename: Gehong
authors.initials: G
authors.lastname: Wei
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000235:genetics; D001673:Biodegradation, Environmental; D007887:Fabaceae / Q000737:chemistry*; D010616:Phenanthrenes / Q000737:chemistry* / Q000378:metabolism; D010802:Phylogeny; D053147:Plant Exudates / Q000737:chemistry / Q000494:pharmacology*; D018517:Plant Roots / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism
chemical_list: D010616:Phenanthrenes; D053147:Plant Exudates; D012989:Soil Pollutants; C031181:phenanthrene
keywords: Bioremediation; Mucilage; PAH mineralization; Phytoremediation; Rhizosphere