Zinc Solubilizing Plant Growth Promoting Microbes Produce Zinc Nanoparticles

Abstract

Strains of Pseudomonas, Bacillus and Azospirillum with plant growth promoting ability were checked for their zinc solubilizing ability. Efficient zinc solubilizers were checked for their ability to produce nano-scale zinc particles. The nanoparticles from the cell-free culture filtrates obtained from these strains were characterized for particle size, Zeta potential and functional groups. Presence of Zn nanoparticles in the bacterial culture filtrate was confirmed by particle distribution and Scanning electron microscope (SEM) analysis. Most properties of nanoparticles are size dependent. Zinc nanoparticles were observed to be spherical in shape and size ranged from 52.0 to 106.0 nm. Zeta potential of the Zn nanoparticles was estimated to understand the stability of the particles. The measured zeta potentials varied from -14.5mV to +179.10 mV indicating high stability and dispersion of the zinc nanoparticles. FTIR peaks at different wave numbers depicted the role of functional groups of proteins in the biosynthesis of Zn nanoparticles. This finding opens a new area of research focusing on microbe-microbe interactions in rhizosphere and plant-microbe interactions at rhizosphere apart from biosynthesis of nanoparticles, which has major applications. To our knowledge, this is the first report of production of nanoparticles as part of nutrient mobilization by plant growth promoting rhizobacteria.