Exploring microbial diversity responses in agricultural fields: a comparative analysis under pesticide stress and non-stress conditions.

Exposure to pesticides changes the microbial community structure in contaminated agricultural fields. To analyze the changes in the native microbial composition qRT-PCR, a metagenomic study was conducted. The qRT-PCR results exhibited that the uncontaminated soil has a higher copy number of 16S rDNA relative to the soil contaminated with pesticide. Metagenome analysis interprets that uncontaminated soil is enriched with proteobacteria in comparison with pesticide-contaminated soil. However, the presence of Actinobacteria, Firmicutes, and Bacteroides was found to be dominant in the pesticide-spiked soil. Additionally, the presence of new phyla such as Chloroflexi, Planctomycetes, and Verrucomicrobia was noted in the pesticide-spiked soil, while Acidobacteria and Crenarchaeota were observed to be extinct. These findings highlight that exposure to pesticides on soil significantly impacts the biological composition of the soil. The abundance of microbial composition under pesticide stress could be of better use for the treatment of biodegradation and bioremediation of pesticides in contaminated environments.

Rhizospheric bacteria: the key to sustainable heavy metal detoxification strategies.

The increasing rate of industrialization, anthropogenic, and geological activities have expedited the release of heavy metals (HMs) at higher concentration in environment. HM contamination resulting due to its persistent nature, injudicious use poses a potential threat by causing metal toxicities in humans and animals as well as severe damage to aquatic organisms. Bioremediation is an emerging and reliable solution for mitigation of these contaminants using rhizospheric microorganisms in an environmentally safe manner. The strategies are based on exploiting microbial metabolism and various approaches developed by plant growth promoting bacteria (PGPB) to minimize the toxicity concentration of HM at optimum levels for the environmental clean-up. Rhizospheric bacteria are employed for significant growth of plants in soil contaminated with HM. Exploitation of bacteria possessing plant-beneficial traits as well as metal detoxifying property is an economical and promising approach for bioremediation of HM. Microbial cells exhibit different mechanisms of HM resistance such as active transport, extra cellular barrier, extracellular and intracellular sequestration, and reduction of HM. Tolerance of HM in microorganisms may be chromosomal or plasmid originated. Proteins such as MerT and MerA of mer operon and czcCBA, ArsR, ArsA, ArsD, ArsB, and ArsC genes are responsible for metal detoxification in bacterial cell. This review gives insights about the potential of rhizospheric bacteria in HM removal from various polluted areas. In addition, it also gives deep insights about different mechanism of action expressed by microorganisms for HM detoxification. The dual-purpose use of biological agent as plant growth enhancement and remediation of HM contaminated site is the most significant future prospect of this article.

Esterase and ALDH dehydrogenase-based pesticide degradation by Bacillus brevis 1B from a contaminated environment.

The isolated bacterial strain (Bacillus brevis strain 1 B) showed a maximum tolerated level of 450 mg L-1 of the selected pesticides namely: imidacloprid, fipronil, cypermethrin, and sulfosulfuron. Within 15 days of the experiment, strain 1 B was able to reduce up to 95% of a pesticide mixture (20 mg L-1) in a carbon-deficient medium (minimal medium). The optimal conditions obtained using Response Surface Methodology (RSM) were: inoculums; 2.0 × 107 CFU mL-1, shaking speed; 120 rpm, and pesticide concentration; 80 mg L-1. After 15 days of soil-based bioremediation using strain 1 B, the degradation pattern for imidacloprid, fipronil, cypermethrin, sulfosulfuron, and control was 99, 98.5, 94, 91.67, and 7%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis was used to determine the intermediate metabolites of cypermethrin with bacterial 1 B as 2-cyclopenten-1-one, 2-methylpyrrolidine, 2-oxonanone, 2-pentenoic acid, 2-penten-1-ol, hexadecanoic acid or palmitic acid, pentadecanoic acid, 3-cyclopentylpropionic acid, and 2-dimethyl. Furthermore, genes encoding aldehyde dehydrogenase (ALDH) and esterase were expressed under stress conditions and connected to pesticide bioremediation. Hence the efficacy of Bacillus brevis (1 B) could be employed for the bioremediation of pesticide mixtures and other toxic substances (dye, polyaromatic hydrocarbon, etc.) from contaminated sites.

Functional characterization and molecular fingerprinting of potential phosphate solubilizing bacterial candidates from Shisham rhizosphere.

Phosphate solubilizing bacteria (PSB) are important role players in plant growth promotion. In the present study, we aimed to screen the functionally active phosphate solubilizing bacteria (PSB) associated with Dalbergia sissoo Roxb. (Shisham) from different provenances. Screening for phosphate solubilization was done on Pikovskaya's agar, and 18 bacteria positive for the tri-calcium phosphate (Ca3(PO4)2 solubilization showing visible dissolution halo zones were identified. All 18 isolates showed zinc solubilization, indole acetic acid (IAA), siderophore, and hydrogen cyanide (HCN) production. The morphological and biochemical characterization with 16S rDNA gene-based phylogenetic analysis identified bacterial strains as belonging to the genus Pseudomonas, Klebsiella, Streptomyces, Pantoea, Kitasatospora, Micrococcus, and Staphylococcus. Among all the isolates, one of the isolates named L4, from Lacchiwala region was the most efficient P solubilizer with a high P solubilization index (4.75 ± 0.06) and quantitative P solubilization activity (891.38 ± 18.55 µg mL-1). The validation of phosphate solubilization activity of PSB isolates was done by amplification of the Pyrroloquinoline quinone (PQQ) genes, pqqA and pqqC. Based on this study, we have selected the bacterial strains which are efficient phosphate solubilizers and could be economical and eco-friendly in plant growth promotion, disease suppression, as an antioxidant, and for subsequent enhancement of yield.

Developments and application of chitosan-based adsorbents for wastewater treatments.

Water quality is deteriorating continuously as increasing levels of toxic inorganic and organic contaminants mostly discharging into the aquatic environment. Removal of such pollutants from the water system is an emerging research area. During the past few years use of biodegradable and biocompatible natural additives has attracted considerable attention to alleviate pollutants from wastewater. The chitosan and its composites emerged as a promising adsorbents due to their low price, abundance, amino, and hydroxyl groups, as well as their potential to remove various toxins from wastewater. However, a few challenges associated with its practical use include lack of selectivity, low mechanical strength, and solubility in acidic medium. Therefore, several approaches for modification have been explored to improve the physicochemical properties of chitosan for wastewater treatment. Chitosan nanocomposites found effective for the removal of metals, pharmaceuticals, pesticides, microplastics from the wastewaters. Nanoparticle doped with chitosan in the form of nano-biocomposites has recently gained much attention and proven a successful tool for water purification. Hence, applying chitosan-based adsorbents with numerous modifications is a cutting-edge approach to eliminating toxic pollutants from aquatic systems with the global aim of making potable water available worldwide. This review presents an overview of distinct materials and methods for developing novel chitosan-based nanocomposites for wastewater treatment.

Biotechnological tools to elucidate the mechanism of pesticide degradation in the environment.

Pesticides are widely used in agriculture, households, and industries; however, they have caused severe negative effects on the environment and human health. To clean up pesticide contaminated sites, various technological strategies, i.e. physicochemical and biological, are currently being used throughout the world. Biological approaches have proven to be a viable method for decontaminating pesticide-contaminated soils and water environments. The biological process eliminates contaminants by utilizing microorganisms' catabolic ability. Pesticide degradation rates are influenced by a variety of factors, including the pesticide's structure, concentration, solubility in water, soil type, land use pattern, and microbial activity in the soil. There is currently a knowledge gap in this field of study because researchers are unable to gather collective information on the factors affecting microbial growth, metabolic pathways, optimal conditions for degradation, and genomic, transcriptomic, and proteomic changes caused by pesticide stress on the microbial communities. The use of advanced tools and omics technology in research can bridge the existing gap in our knowledge regarding the bioremediation of pesticides. This review provides new insights on the research gaps and offers potential solutions for pesticide removal from the environment through the use of various microbe-mediated technologies.

Novel mechanism and degradation kinetics of pesticides mixture using Bacillus sp. strain 3C in contaminated sites.

The present study has investigated the potential of Bacillus sp. strain 3C able to degrade mixture of pesticides from the environment. It showed maximum tolerance up to 450 mg·L-1 for cypermethrin, fipronil, imidacloprid and sulfosulfuron. The strain 3C was able to degrade up to the 94% of mixture of pesticides (20 mg·L-1) within 15 days of experiment. The Box-Behnken design of Response Surface Methodology (RSM) determined the optimized conditions as; inoculum size 3.0 × 107 CFU·mL-1, shaking speed 120 rpm, and pesticides concentration 80 mg·L-1. In soil-based bioremediation with strain 3C after 15 days degradation pattern was; 99, 94, 92, 92 and 7% for the imidacloprid, sulfosulfuron, fipronil, cypermethrin and control respectively. The novel intermediate metabolites for cypermethrin degradation were investigated as decyl isobutyl ester, phthalic acid, cyclopropane carboxylic acid tri dec-2-ynyl ester, 9- octadecanal, tridecane, propanoic acid, cyclohexene, bicyclo[2.2.1] heptan-2-ol, and acetic acid were identified using Gas chromatography Mass Spectrometry (GC-MS) with strain 3C. Moreover, the results of the laccase based enzymatic kinetics suggested that the rate of production was maximum in pesticides stress (94 µg·µL-1) whereas, in normal condition 51 µg·µL-1. The Km value found to be decreased in pesticides stress condition 12.25 and increment in Km 13.58 mM was observed without stress. Furthermore, aldehyde dehydrogenase (ALDH) and laccase encoding genes were amplified and linked with mixture of pesticides bioremediation. The efficiency of bacterial strain 3C, could be used for bioremediation of mixture of pesticides, and other xenobiotic compounds from the contaminated environments.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment.

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

Differential proteomic analysis under pesticides stress and normal conditions in Bacillus cereus 2D.

A potential pesticide degrading bacterial isolate (2D), showing maximum tolerance (450 mg∙L-1) for cypermethrin, fipronil, imidacloprid and sulfosulfuron was recovered from a pesticide contaminated agricultural field. The isolate degraded cypermethrin, imidacloprid, fipronil and sulfosulfuron in minimal salt medium with 94, 91, 89 and 86% respectively as revealed by high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis after 15 days of incubation. Presence of cyclobutane, pyrrolidine, chloroacetic acid, formic acid and decyl ester as major intermediate metabolites of cypermethrin biodegradation was observed in gas chromatography mass spectrometry (GC-MS) analysis. Results based on 16S rDNA sequencing, and phylogenetic analysis showed maximum similarity of 2D with Bacillus cereus (Accession ID: MH341691). Stress responsive and catabolic/pesticide degrading proteins were over expressed in the presence of cypermethrin in bacteria. Enzymatic kinetics of laccase was deduced in the test isolate under normal and pesticide stress conditions which suggested that the production of enzyme was induced significantly in pesticide stress (163 µg.µL-1) as compare to normal conditions(29 µg.µL-1) while the Km value was decreased in pesticides stress condition (Km = 10.57 mM) and increases in normal condition (Km = 14.33 mM).Amplification of laccase gene showed a major band of 1200bp. The present study highlights on the potential of 2D bacterial strain i.e., high tolerance level of pesticide, effective biodegradation rate, and presence of laccase gene in bacterial strain 2D, could become a potential biological agent for large-scale treatment of mixture of pesticide (cypermethrin, fipronil, imidacloprid and sulfosulfuron) in natural environment (soil and water).

Contribution of zinc solubilizing bacterial isolates on enhanced zinc uptake and growth promotion of maize (Zea mays L.).

Zinc-solubilizing bacteria, namely Burkholderia cepacia and Acinetobacter baumannii (H1 and H3, respectively), able to grow in liquid basal medium supplemented with ZnO, Zn3 (PO4)2, and ZnSO4·7H2O (0.1%), showed plant growth promoting properties. The treatment of Acinetobacter baumannii (H3) solubilizes the ZnO (1.42 ppm), Zn3 (PO4)2 (1.15 ppm), and ZnSO4·7H2O (1.44 ppm).The maximum solubilization of ZnSO4·7H2O (1.42 ppm) was observed in Burkholderia cepacia (H1) after 15 days. Organic acids produced by the bacteria decreased the pH of the medium and helped in Zn solubilization. In pot experiment on maize, Burkholderia cepacia (H1) treatment significantly enhanced plant height and root length in the presence of ZnO (2%) added in 10 mL of inoculum in each pot. High-performance liquid chromatography (HPLC) analysis of maize root extract showed the presence of oxalic, maleic, tartaric, and fumaric acid after 60 days of the experiment. Bacterial treatments enhanced sugar and protein level in maize plants and were 55.2 and 42.55 µg/mL plant extract, respectively, under mixture of bacterial treatment. Hence, isolates H1 and H3 expressed highest potential throughout the experiments, as zinc solubilizers and plant growth-promoting strains. This study demonstrated that meticulous use of Zn-solubilizing bacterial strains could aid in enhanced plant growth and can be the potential bio-inoculants for biofortification of maize to overcome the problems of malnutrition.