title: The role of gluconate production by Pseudomonas spp. in the mineralization and bioavailability of calcium-phytate to Nicotiana tabacum.
abstract: Organic phosphorus (P) is abundant in most soils but is largely unavailable to plants. Pseudomonas spp. can improve the availability of P to plants through the production of phytases and organic anions. Gluconate is a major component of Pseudomonas organic anion production and may therefore play an important role in the mineralization of insoluble organic P forms such as calcium-phytate (CaIHP). Organic anion and phytase production was characterized in 2 Pseudomonas spp. soil isolates (CCAR59, Ha200) and an isogenic mutant of strain Ha200, which lacked a functional glucose dehydrogenase (Gcd) gene (strain Ha200 gcd::Tn5B8). Wild-type and mutant strains of Pseudomonas spp. were evaluated for their ability to solubilize and hydrolyze CaIHP and to promote the growth and assimilation of P by tobacco plants. Gluconate, 2-keto-gluconate, pyruvate, ascorbate, acetate, and formate were detected in Pseudomonas spp. supernatants. Wild-type pseudomonads containing a functional gcd could produce gluconate and mineralize CaIHP, whereas the isogenic mutant could not. Inoculation with Pseudomonas improved the bioavailability of CaIHP to tobacco plants, but there was no difference in plant growth response due to Gcd function. Gcd function is required for the mineralization of CaIHP in vitro; however, further studies will be needed to quantify the relative contribution of specific organic anions such as gluconate to plant growth promotion by soil pseudomonads.
authors.affiliation: a The James Hutton Institute, Invergowrie, Dundee, Scotland, DD2 5DA, UK.
authors.forename: Courtney D
authors.initials: CD
authors.lastname: Giles
authors.affiliation: b AgResearch Lincoln, Innovative Farm Systems, Christchurch 8140, New Zealand.
authors.forename: Pei-Chun Lisa
authors.initials: PC
authors.lastname: Hsu
authors.affiliation: c CSIRO Agriculture, GPO Box 1600, Canberra, ACT 2601, Australia.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Richardson
authors.affiliation: b AgResearch Lincoln, Innovative Farm Systems, Christchurch 8140, New Zealand.
authors.forename: Mark R H
authors.initials: MR
authors.lastname: Hurst
authors.affiliation: d Dartmouth College, Thayer School of Engineering, Hanover, NH 037553, USA.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Hill
mesh_terms: D010832:6-Phytase / Q000235:genetics; D001682:Biological Availability; D002118:Calcium / Q000378:metabolism*; D005942:Gluconates / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism*; D011549:Pseudomonas / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012988:Soil Microbiology; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology
chemical_list: D005942:Gluconates; D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase; C030691:gluconic acid; D002118:Calcium
keywords: gluconate; phosphore; phosphorus; phytase; pseudomonades; pseudomonads; rhizosphere; rhizosphère