title: Functional characterization of a soybean growth stimulator Bradyrhizobium sp. strain SR-6 showing acylhomoserine lactone production.
abstract: A soybean nodule endophytic bacterium Bradyrhizobium sp. strain SR-6 was characterized for production of acyl homoserine lactones (AHLs) as quorum sensing molecules. Mass spectrometry analysis of AHLs revealed the presence of C6-HSL, 3OH-C6-HSL, C8-HSL, C10-HSL, 3oxoC10-HSL, 3oxo-C12-HSL and 3OH-C12-HSL which are significantly different from those reported earlier in soybean symbionts. Purified AHL extracts significantly improved wheat and soybean seedling growth and root hair development along with increased soybean nodulation under axenic conditions. A positive correlation was observed among in vivo nitrogenase and catalase enzyme activities of the strain SR-6. Transmission electron microscopic analysis showed the cytochemical localization of catalase activity within the bacteroids, specifically attached to the peribacteroidal membrane. Root and nodule colonization proved rhizosphere competence of SR-6. The inoculation of SR-6 resulted in increased shoot length (13%), plant dry matter (50%), grain weight (16%), seed yield (20%) and N-uptake (14%) as compared to non-inoculated soybean plants. The symbiotic bacterium SR-6 has potential to improve soybean growth and yield in sub-humid climate of Azad Jammu and Kashmir region of Pakistan. The production and mass spectrometric profiling of AHLs as well as in vivo cytochemical localization of catalase enzyme activity in soybean Bradyrhizobium sp. have never been reported earlier elsewhere before our these investigations.
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan.
authors.forename: Amanat
authors.initials: A
authors.lastname: Ali
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan.
authors.lastname: Ayesha
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan shameed58@hotmail.com.
authors.forename: Sohail
authors.initials: S
authors.lastname: Hameed
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan.
authors.forename: Asma
authors.initials: A
authors.lastname: Imran
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan.
authors.forename: Mazhar
authors.initials: M
authors.lastname: Iqbal
authors.affiliation: Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Jhang Road, PO Box no. 577, Faisalabad 38000, Pakistan.
authors.forename: Javed
authors.initials: J
authors.lastname: Iqbal
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canada.
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Oresnik
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism* / Q000494:pharmacology; D020369:Bradyrhizobium / Q000201:enzymology / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology; D002374:Catalase / Q000032:analysis; D013025:Glycine max / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D013559:Symbiosis
chemical_list: D054742:Acyl-Butyrolactones; D002374:Catalase
keywords: Bradyrhizobium; acyl homoserine lactones; catalase enzyme; nitrogenase activity; soybean