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.

PGPR mediated Zinc biofertilization of soil and its impact on growth and productivity of wheat

“…We have also characterized zinc biosorption by this strain (Upadhyay and Srivastava 2014) In the present communication, we demonstrate the zinc biofertilization potential of this strain and its impact on the growth and development of wheat crop.…”

Players over the Surface: Unraveling the Role of Exopolysaccharides in Zinc Biosorption by Fluorescent Pseudomonas Strain Psd

“…The shake cultures were raised on Controlled Environment Shaker Incubator (Kühner, Switzerland) at 200 rpm at 30°C for the required period of time. Growth was determined turbidometrically at 600 nm, as per the protocol described earlier (Upadhyay and Srivastava, 2014 ). All chemicals used in the study were of analytical grade and purchased from Sigma Aldrich (St. Louis, MO, USA).…”

“…Fluorescent Pseudomonas strain Psd is a rhizosphere isolate, possessing multiple PGP properties and biocontrol potential (Upadhyay and Srivastava, 2008 , 2010 ; Kochar et al, 2011 ). Besides, we have earlier demonstrated that this strain possesses high resistance toward Zn 2+ , which emanates from extracellular biosorption (Upadhyay and Srivastava, 2014 ). We have also established that Zn 2+ biosorption is coupled with an increase in the total EPS production.…”

“…Microbial communities, like all other organisms, have adapted themselves to the metal concentrations encountered by two major strategies, namely avoidance and sequestration. Based on these strategies, the major mechanisms operating in the prokaryotes that maintain cellular Zn 2+ concentration can be classified into: (i) physico-chemical interactions (adsorption or biosorption to cell wall and other constituents); (ii) regulated import; (iii) efflux; and (iv) sequestration (Ledin, 2000 ; Choudhury and Srivastava, 2001 ; Blencowe and Morby, 2003 ; Upadhyay and Srivastava, 2014 ).…”

Phosphorus Efficiency in Wheat as Affected by Foliar Spray with Zinc, Humic Acid and Biofertilizer (Bacillus megatherium sp.) Addition Under Calcareous Soil Conditions

“…Plant growth promoting rhizobacteria (PGPR) have been known for long time to be involved in plant growth promotion via mechanisms such as phytohormone production, suppression of plant diseases and improved nutrient acquisition by nitrogen fixation, phosphate solubilization and metal accumulation (Martínez Viveros et al 2010, Upadhyay andSrivastava 2014). Apart from this, PGPR are also known to be key players in bioremediation of contaminated soils due to their ability to accumulate metals (Zhuang et al 2007).…”