title: Elucidating the interactions and phytotoxicity of zinc oxide nanoparticles with agriculturally beneficial bacteria and selected crop plants.
abstract: There is a growing interest in the use of bioinoculants to assist mineral fertilizers in improving crop production and yield. Azotobacter and Pseudomonas are two agriculturally relevant strains of bacteria which have been established as efficient bioinoculants. An experiment involving addition of graded concentrations of zinc oxide (ZnO) nanoparticles was undertaken using log phase cultures of Azotobacter and Pseudomonas. Growth kinetics revealed a clear trend of gradual decrease with Pseudomonas; however, Azotobacter exhibited a twofold enhancement in growth with increase in the concentration of ZnO concentration. Scanning electron microscopy (SEM), supported by energy-dispersive X-ray (EDX) analyses, illustrated the significant effect of ZnO nanoparticles on Azotobacter by the enhancement in the abundance of globular biofilm-like structures and the intracellular presence of ZnO, with the increase in its concentration. It can be surmised that extracellular mucilage production in Azotobacter may be providing a barrier to the nanoparticles. Further experiments with Azotobacter by inoculation of wheat and tomato seeds with ZnO nanoparticles alone or bacteria grown on ZnO-infused growth medium revealed interesting results. Vigour index of wheat seeds reduced by 40-50% in the presence of different concentrations of ZnO nanoparticles alone, which was alleviated by 15-20%, when ZnO and Azotobacter were present together. However, a drastic 50-60% decrease in vigour indices of tomato seeds was recorded, irrespective of Azotobacter inoculation.
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.|Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA.
authors.forename: Anuraag
authors.initials: A
authors.lastname: Boddupalli
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Rameshwar
authors.initials: R
authors.lastname: Tiwari
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Anamika
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Surender
authors.initials: S
authors.lastname: Singh
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. radhapr@gmail.com.
authors.forename: Radha
authors.identifier: http://orcid.org/0000-0002-1622-9817
authors.initials: R
authors.lastname: Prasanna
authors.affiliation: Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Lata
authors.initials: L
authors.lastname: Nain
mesh_terms: D001395:Azotobacter / Q000187:drug effects* / Q000254:growth & development; D058491:Bacterial Load; D018441:Biofilms / Q000187:drug effects; D018556:Crops, Agricultural / Q000187:drug effects*; D018551:Solanum lycopersicum / Q000187:drug effects*; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000378:metabolism / Q000633:toxicity; D011549:Pseudomonas / Q000187:drug effects* / Q000254:growth & development; D013052:Spectrometry, X-Ray Emission; D014908:Triticum / Q000187:drug effects*; D015034:Zinc Oxide / Q000378:metabolism* / Q000633:toxicity*
chemical_list: D015034:Zinc Oxide
keywords: Azotobacter; Nanoparticles; Phyotoxicity; Vigour index; Zinc oxide