title: Characterization of plant growth promoting rhizobacteria isolated from polluted soils and containing 1-aminocyclopropane-1-carboxylate deaminase.
abstract: Fifteen bacterial strains containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase were isolated from the rhizoplane of pea (Pisum sativum L.) and Indian mustard (Brassica juncea L.) grown in different soils and a long-standing sewage sludge contaminated with heavy metals. The isolated strains were characterized and assigned to various genera and species, such as Pseudomonas brassicacearum, Pseudomonas marginalis, Pseudomonas oryzihabitans, Pseudomonas putida, Pseudomonas sp., Alcaligenes xylosoxidans, Alcaligenes sp., Variovorax paradoxus, Bacillus pumilus, and Rhodococcus sp. by determination of 16S rRNA gene sequences. The root elongation of Indian mustard and rape (Brassica napus var. oleifera L.) germinating seedlings was stimulated by inoculation with 8 and 13 isolated strains, respectively. The bacteria were tolerant to cadmium toxicity and stimulated root elongation of rape seedlings in the presence of 300 microM CdCl2 in the nutrient solution. The effect of ACC-utilising bacteria on root elongation correlated with the impact of aminoethoxyvinylglycine and silver ions, chemical inhibitors of ethylene biosynthesis. A significant improvement in the growth of rape caused by inoculation with certain selected strains was also observed in pot experiments, when the plants were cultivated in cadmium-supplemented soil. The biomass of pea cv. Sparkle and its ethylene sensitive mutant E2 (sym5), in particular, was increased through inoculation with certain strains of ACC-utilising bacteria in pot experiments in quartz sand culture. The beneficial effect of the bacteria on plant growth varied significantly depending on individual bacterial strains, plant genotype, and growth conditions. The results suggest that plant growth promoting rhizobacteria containing ACC deaminase are present in various soils and offer promise as a bacterial inoculum for improvement of plant growth, particularly under unfavourable environmental conditions.
authors.affiliation: Laboratory of Biological Nitrogen, All-Russia Research Institute for Agricultural Microbiology, Saint Petersburg, Russian Federation. belimov@rambler.ra
authors.forename: A A
authors.initials: AA
authors.lastname: Belimov
authors.forename: V I
authors.initials: VI
authors.lastname: Safronova
authors.forename: T A
authors.initials: TA
authors.lastname: Sergeyeva
authors.forename: T N
authors.initials: TN
authors.lastname: Egorova
authors.forename: V A
authors.initials: VA
authors.lastname: Matveyeva
authors.forename: V E
authors.initials: VE
authors.lastname: Tsyganov
authors.forename: A Y
authors.initials: AY
authors.lastname: Borisov
authors.forename: I A
authors.initials: IA
authors.lastname: Tikhonovich
authors.forename: C
authors.initials: C
authors.lastname: Kluge
authors.forename: A
authors.initials: A
authors.lastname: Preisfeld
authors.forename: K J
authors.initials: KJ
authors.lastname: Dietz
authors.forename: V V
authors.initials: VV
authors.lastname: Stepanok
mesh_terms: D001419:Bacteria / Q000145:classification / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification; D001937:Brassica / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D002104:Cadmium / Q000494:pharmacology; D019755:Carbon-Carbon Lyases / Q000378:metabolism*; D005030:Ethylenes / Q000494:pharmacology; D018532:Pisum sativum / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D012722:Sewage / Q000382:microbiology; D012988:Soil Microbiology; D012989:Soil Pollutants
chemical_list: D005030:Ethylenes; D012722:Sewage; D012989:Soil Pollutants; D002104:Cadmium; C036216:ethylene; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases