title: Organic acid exudation and pH changes by Gordonia sp. and Pseudomonas fluorescens grown with P adsorbed to goethite.
abstract: The actinomycete Gordonia sp. and the bacterium Pseudomonas fluorescens Pf-5 were grown in liquid media (pH 6.5) with phosphate adsorbed to the Fe-oxide/hydroxide goethite (Goe-P) and with soluble phosphate (0.1 mM or 1.0 mM P as KH2PO4). The two isolates showed distinct differences in their physiology. The pH of the medium was increased by Gordonia sp. by 1.1-1.7 units while it was decreased by P. fluorescens by 1.4-2.4 units. In all treatments the concentration of organic acids in the media with Gordonia sp. was up to 10 times lower (0.4-10.9 micromol L(-1)) than in media with P. fluorescens (33.4-84.4 micromol L(-1)). Gordonia sp. produced five different organic acids in varying amounts depending on P source and time. In contrast, P. fluorescens exuded mainly citrate and only small amounts of two to three other organic acids irrespective of P source or time.
authors.affiliation: Institute for Applied Botany, University of Hamburg, Ohnhorststrasse 18, 22609 Hamburg, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Hoberg
authors.forename: Petra
authors.initials: P
authors.lastname: Marschner
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lieberei
mesh_terms: D000327:Adsorption; D002264:Carboxylic Acids / Q000378:metabolism*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry*; D033601:Gordonia Bacterium / Q000254:growth & development* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry; D008903:Minerals; D010710:Phosphates / Q000737:chemistry; D011551:Pseudomonas fluorescens / Q000254:growth & development* / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D003470:Culture Media; D058085:Iron Compounds; D008903:Minerals; D010710:Phosphates; C094886:goethite