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.

CuO and ZnO Nanoparticles Modify Interkingdom Cell Signaling Processes Relevant to Crop Production

“…Microbial populations are greater in the rhizosphere, the region around the root influenced by exudation of plant metabolites, than in the surrounding soil . These plant exudates provide nutrients to support microbial growth. − However, the complex microbial community structure in soils is disturbed by NP amendments, with both increases and decreases for certain taxa occurring dependent on NP, plant, and soil properties. , The soil microbes involved in the nitrogen cycle are among those with documented sensitivity. − Changes in function of a population, such as a loss in function of nitrogen-fixing rhizobium isolates, would in turn affect plant performance. ,, Clearly, any formulation for agricultural use should not have deleterious effects on the organisms involved in essential element cycling …”

Impact of nanoparticles on transcriptional regulation of catabolic genes of petroleum hydrocarbon‐degrading bacteria in contaminated soil microcosms

“…ZnO‐NPs are amongst NPs with high production volume and therefore a high environmental release risk . In soil, it may have a selective deteriorating effect on certain beneficial microorganisms . In this study, it has been found that ZnO‐NPs treatment in low concentration (1 μg ml −1 ) neither had a severe effect on the OTUs in soil samples, specially, Bacillus sp.…”

“…With the dramatic increase in the use of NPs, a new approach for the environmental risk assessment of NPs is urgently needed . Treatment of soil with NPs usually results in antimicrobial effect on certain valuable soil microorganisms in particular or overall microbial community . We are much concerned with the impact of NPs and their serious effects on microbial community structure and natural biodegradation process provided by endogenous bacterial populations in contaminated soils.…”

“…The use of NPs in water treatment facilities increased the concern that it might jeopardize ecosystems. NPs showed significant efficacy to remove microbial contaminants like bacteria, fungi, virus, molds, etc., owing to large surface to volume ratios offered by nanostructures . However, the difficulty of removing nanoparticles after the treatment is the biggest limitation in its use for practical applications.…”

Mechanism, of Biophysicochemical Interactions and Cellular Uptake at the Nano-Bio Interface: A Review

“…Insertion of hydrophobic nanoparticles into lipid membranes poses a great challenge since the membranes are destroyed during the loading process [46,47]. Macroscopically visible effects include curving of the lipid membrane, budding or fission effects [48,49]. Negatively charged nanoparticles often result in clustering effects thus reducing charge movement/transfer and increasing the gel phase of the involved lipids [50].…”