title: Mechanism of zinc resistance in a plant growth promoting Pseudomonas fluorescens strain.
abstract: Bacterial systems have evolved a number of mechanisms, both active and passive, to manage toxic concentrations of heavy metals in their environment. The present study is aimed at describing the zinc resistance mechanism in a rhizospheric isolate, Pseudomonas fluorescens strain Psd. The strain was able to sustain an external Zn(2+) concentration of up to 5 mM in the medium. The strategy for metal management by the strain was found to be extracellular biosorption with a possible role of exopolysaccharides in metal accumulation. The attainment of equilibrium in biosorption reaction was found to be dependent on initial Zn(2+) concentration, with the reaction reaching equilibrium faster (50 min) at high initial Zn(2+) concentration. Biosorption kinetics of the process was adjusted to pseudo-first order rate equation. With the help of Langmuir and Freundlich adsorption isotherms, it was established that Zn(2+) biosorption by the bacterium is a thermodynamically favourable process.
authors.affiliation: Department of Genetics, University of Delhi South Campus, New Delhi, 110021, India.
authors.forename: Anamika
authors.initials: A
authors.lastname: Upadhyay
authors.forename: Sheela
authors.initials: S
authors.lastname: Srivastava
mesh_terms: D003470:Culture Media; D007700:Kinetics; D019216:Metals, Heavy / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D011551:Pseudomonas fluorescens / Q000302:isolation & purification* / Q000502:physiology*; D013816:Thermodynamics; D015032:Zinc / Q000378:metabolism*
chemical_list: D003470:Culture Media; D019216:Metals, Heavy; D011135:Polysaccharides, Bacterial; C064841:exopolysaccharide, Pseudomonas; D015032:Zinc