Ecotoxicological implications of residual pesticides to beneficial soil bacteria: A review

From growth inhibition to ultrastructural changes: Toxicological assessment of lambda cyhalothrin and fosetyl aluminium against Bacillus subtilis and Pseudomonas aeruginosa

In modern agricultural practices, agrochemicals and pesticides play an important role in protecting the crops from pests and elevating agricultural productivity. This strategic utilization is essential to meet global food demand due to the relentless growth of the world's population. However, the indiscriminate application of these substances may result in environmental hazards and directly affect the soil microorganisms and crop production. Considering this, an in vitro study was carried out to evaluate the pesticides' effects i.e. lambda cyhalothrin (insecticide) and fosetyl aluminum (fungicide) at lower, recommended, and higher doses on growth behavior, enzymatic profile, total soluble protein production, and lipid peroxidation of bacterial specimens (Pseudomonas aeruginosa and Bacillus subtilis). The experimental findings demonstrated a concentration-dependent decrease in growth of both tested bacteria, when exposed to fosetyl aluminium concentrations exceeding the recommended dose. This decline was statistically significant (p < 0.000). However, lambda cyhalothrin at three times of recommended dose induces 10% increase in growth of Pseudomonas aeruginosa (P. aeruginosa) and 76.8% decrease in growth of Bacillus subtilis (B. subtilis) respectively as compared to control. These results showed the stimulatory effect of lambda cyhalothrin on P. aeruginosa and inhibitory effect on B. subtilis. Pesticides induced notable alterations in biomarker enzymatic assays and other parameters related to oxidative stress among bacterial strains, resulting in increased oxidative stress and membrane permeability. Generally, the maximum toxicity of both (P. aeruginosa and B. subtilis) was shown by fosetyl aluminium, at three times of recommended dose. Fosetyl aluminium induced morphological changes like cellular cracking, reduced viability, aberrant margins and more damage in both bacterial strains as compared to lambda cyhalothrin when observed under scanning electron microscope (SEM). Conclusively the, present study provide an insights into a mechanistic approach of pyrethroid insecticide and phosphonite fungicide induced cellular toxicity towards bacteria.

PGPR-Enabled bioremediation of pesticide and heavy metal-contaminated soil: A review of recent advances and emerging challenges

The excessive usage of agrochemicals, including pesticides, along with various reckless human actions, has ensued discriminating prevalence of pesticides and heavy metals (HMs) in crop plants and the environment. The enhanced exposure to these chemicals is a menace to living organisms. The pesticides may get bioaccumulated in the food chain, thereby leading to several deteriorative changes in the ecosystem health and a rise in the cases of some serious human ailments including cancer. Further, both HMs and pesticides cause some major metabolic disturbances in plants, which include oxidative burst, osmotic alterations and reduced levels of photosynthesis, leading to a decline in plant productivity. Moreover, the synergistic interaction between pesticides and HMs has a more serious impact on human and ecosystem health. Various attempts have been made to explore eco-friendly and environmentally sustainable methods of improving plant health under HMs and/or pesticide stress. Among these methods, the employment of PGPR can be a suitable and effective strategy for managing these contaminants and providing a long-term remedy. Although, the application of PGPR alone can alleviate HM-induced phytotoxicities; however, several recent reports advocate using PGPR with other micro- and macro-organisms, biochar, chelating agents, organic acids, plant growth regulators, etc., to further improve their stress ameliorative potential. Further, some PGPR are also capable of assisting in the degradation of pesticides or their sequestration, reducing their harmful effects on plants and the environment. This present review attempts to present the current status of our understanding of PGPR's potential in the remediation of pesticides and HMs-contaminated soil for the researchers working in the area.

Unlocking the interaction of organophosphorus pesticide residues with ecosystem: Toxicity and bioremediation

Organophosphorus adulteration in the environment creates terrestrial and aquatic pollution. It causes acute and subacute toxicity in plants, humans, insects, and animals. Due to the excessive use of organophosphorus pesticides, there is a need to develop environmentally friendly, economical, and bio-based strategies. The microbiomes, that exist in the soil, can reduce the devastating effects of organophosphates. The use of cell-free enzymes and yeast is also an advanced method for the degradation of organophosphates. Plant-friendly bacterial strains, that exist in the soil, can help to degrade these contaminants by oxidation-reduction reactions, enzymatic breakdown, and adsorption. The bacterial strains mostly from the genus Bacillus, Pseudomonas, Acinetobacter, Agrobacterium, and Rhizobium have the ability to hydrolyze the bonds of organophosphate compounds like profenofos, quinalphos, malathion, methyl-parathion, and chlorpyrifos. The native bacterial strains also promote the growth abilities of plants and help in detoxification of organophosphate residues. This bioremediation technique is easy to use, relatively cost-effective, very efficient, and ensures the safety of the environment. This review covers the literature gap by describing the major effects of organophosphates on the ecosystem and their bioremediation by using native bacterial strains.

A review of the impact of herbicides and insecticides on the microbial communities

Enhancing crop yield to accommodate the ever-increasing world population has become critical, and diminishing arable land has pressured current agricultural practices. Intensive farming methods have been using more pesticides and insecticides (biocides), culminating in soil deposition, negatively impacting the microbiome. Hence, a deeper understanding of the interaction and impact of pesticides and insecticides on microbial communities is required for the scientific community. This review highlights the recent findings concerning the possible impacts of biocides on various soil microorganisms and their diversity. This review's bibliometric analysis emphasised the recent developments' statistics based on the Scopus document search. Pesticides and insecticides are reported to degrade microbes' structure, cellular processes, and distinct biochemical reactions at cellular and biochemical levels. Several biocides disrupt the relationship between plants and their microbial symbionts, hindering beneficial biological activities that are widely discussed. Most microbial target sites of or receptors are biomolecules, and biocides bind with the receptor through a ligand-based mechanism. The biomarker action mechanism in response to biocides relies on activating the receptor site by specific biochemical interactions. The production of electrophilic or nucleophilic species, free radicals, and redox-reactive agents are the significant factors of biocide's metabolic reaction. Most studies considered for the review reported the negative impact of biocides on the soil microbial community; hence, technological development is required regarding eco-friendly pesticide and insecticide, which has less or no impact on the soil microbial community.

Nontarget impacts of neonicotinoids on nectar-inhabiting microbes

Plant-systemic neonicotinoid (NN) insecticides can exert non-target impacts on organisms like beneficial insects and soil microbes. NNs can affect plant microbiomes, but we know little about their effects on microbial communities that mediate plant-insect interactions, including nectar-inhabiting microbes (NIMs). Here we employed two approaches to assess the impacts of NN exposure on several NIM taxa. First, we assayed the in vitro effects of six NN compounds on NIM growth using plate assays. Second, we inoculated a standardised NIM community into the nectar of NN-treated canola (Brassica napus) and assessed microbial survival and growth after 24 h. With few exceptions, in vitro NN exposure tended to decrease bacterial growth metrics. However, the magnitude of the decrease and the NN concentrations at which effects were observed varied substantially across bacteria. Yeasts showed no consistent in vitro response to NNs. In nectar, we saw no effects of NN treatment on NIM community metrics. Rather, NIM abundance and diversity responded to inherent plant qualities like nectar volume. In conclusion, we found no evidence that NIMs respond to field-relevant NN levels in nectar within 24 h, but our study suggests that context, specifically assay methods, time and plant traits, is important in assaying the effects of NNs on microbial communities.

The looming threat of profenofos organophosphate and microbes in action for their sustainable degradation

Organophosphates are the most extensively used class of pesticides to deal with increasing pest diversity and produce more on limited terrestrial areas to feed the ever-expanding global population. Profenofos, an organophosphate group of non-systematic insecticides and acaricides, is used to combat aphids, cotton bollworms, tobacco budworms, beet armyworms, spider mites, and lygus bugs. Profenofos was inducted into the system as a replacement for chlorpyrifos due to its lower toxicity and half-life. It has become a significant environmental concern due to its widespread presence. It accumulates in various environmental components, contaminating food, water, and air. As a neurotoxic poison, it inhibits acetylcholinesterase receptor activity, leading to dizziness, paralysis, and pest death. It also affects other eukaryotes, such as pollinators, birds, mammals, and invertebrates, affecting ecosystem functioning. Microbes directly expose themselves to profenofos and adapt to these toxic compounds over time. Microbes use these toxic compounds as carbon and energy sources and it is a sustainable and economical method to eliminate profenofos from the environment. This article explores the studies and developments in the bioremediation of profenofos, its impact on plants, pollinators, and humans, and the policies and laws related to pesticide regulation. The goal is to raise awareness about the global threat of profenofos and the role of policymakers in managing pesticide mismanagement.

Efficacy of rhizobacteria Paenibacillus polymyxa SY42 for the biological control of Atractylodes chinensis root rot

Atractylodes chinensis is one of the most commonly used bulk herbs in East Asia; however, root rot can seriously affect its quality and yields. In contrast to chemical pesticides, biological control strategies are environmentally compatible and safe. For this study, 68 antagonistic bacterial strains were isolated from the rhizospheres of healthy Atractylodes chinensis. Strain SY42 exhibited the most potent fungicidal activities, with inhibition rates against F. oxysporum, F. solani, and F. redolens of 67.07 %, 63.40 % and 68.45 %, respectively. Through morphological observation and molecular characterization, strain SY42 was identified as Paenibacillus polymyxa. The volatile organic components (VOCs) produced by SY42 effectively inhibited the mycelial growth of pathogenic fungi through diffusion. SY42 significantly inhibited the germination of pathogenic fungal spores. Following co-culturing with SY42, the mycelium of the pathogenic fungus was deformed, folded, and even ruptured. SY42 could produce cellulases and proteases to degrade fungal cell walls. Pot experiments demonstrated the excellent biocontrol efficacy of SY42. This study revealed that P. polymyxa SY42 inhibited pathogenic fungi through multiple mechanisms, which verified its utility as a biocontrol agent for the control of A. chinensis root rot.

Disturbance mitigation of thiencarbazone-methyl·isoxaflutole on bacterial communities through nitrification inhibitor and attapulgite

There is a knowledge gap in the interaction between the effects of herbicide thiencarbazone-methyl·isoxaflutole on soil microflora and environmental parameters, which leads to a lack of measures in mitigating damage to bacterial communities from the herbicide use. The impacts of thiencarbazone-methyl·isoxaflutole and soil parameters on the diversity, structure and functions of soil bacterial communities were clarified, and the effects and potential mitigation mechanisms of nitrapyrin and modified attapulgite with bacterial function intervention on bacterial communities were explored through incubation and field experiments. The results showed that as thiencarbazone-methyl·isoxaflutole application increased, the stress on soil bacterial community structure and diversity also increased. The relative abundance of bacteria including Aridibacter and GP7 and functional annotations including "nitrate_reduction" were significantly negatively correlated with thiencarbazone-methyl·isoxaflutole residues in soils. The remarkable toxic effects on the Adhaeribacter bacteria were detected at the recommended dose of thiencarbazone-methyl·isoxaflutole application. The residue of isoxaflutole (one of the effective ingredients of thiencarbazone-methyl·isoxaflutole) directly and more strongly affected the diversity of soil bacterial communities than thiencarbazone-methyl. Increasing soil pH was recognised as an important factor in improving the diversity and structure of soil microflora based on the results of the Mantel test and canonical correspondence analysis. Supplemental use of nitrapyrin or modified attapulgite was found to increase soil pH, and further improve the expression of "manganese oxidation" function annotation. This contributed to the increased bacterial diversity (Shannon index). Therefore, the disturbance of soil microflora caused by thiencarbazone-methyl·isoxaflutole application can be mitigated by the use of nitrapyrin and modified attapulgite through raising soil pH.

Present status of insecticide impacts and eco-friendly approaches for remediation-a review

Insecticides are indispensable for modern agriculture to ensuring crop protection and optimal yields. However, their excessive use raises concerns regarding their adverse effects on agriculture and the environment. This study examines the impacts of insecticides on agriculture and proposes remediation strategies. Excessive insecticide application can lead to the development of resistance in target insects, necessitating higher concentrations or stronger chemicals, resulting in increased production costs and disruption of natural pest control mechanisms. In addition, non-target organisms, such as beneficial insects and aquatic life, suffer from the unintended consequences of insecticide use, leading to ecosystem imbalances and potential food chain contamination. To address these issues, integrated pest management (IPM) techniques that combine judicious insecticide use with biological control and cultural practices can reduce reliance on chemicals. Developing and implementing selective insecticides with reduced environmental persistence is crucial. Promoting farmer awareness of responsible insecticide use, offering training and resources, and adopting precision farming technologies can minimize overall insecticide usage.

Pesticide-tolerant microbial consortia: Potential candidates for remediation/clean-up of pesticide-contaminated agricultural soil

Reclamation of pesticide-polluted lands has long been a difficult endeavour. The use of synthetic pesticides could not be restricted due to rising agricultural demand. Pesticide toxicity has become a pressing agronomic problem due to its adverse impact on agroecosystems, agricultural output, and consequently food security and safety. Among different techniques used for the reclamation of pesticide-polluted sites, microbial bioremediation is an eco-friendly approach, which focuses on the application of resilient plant growth promoting rhizobacteria (PGPR) that may transform or degrade chemical pesticides to innocuous forms. Such pesticide-resilient PGPR has demonstrated favourable effects on soil-plant systems, even in pesticide-contaminated environments, by degrading pesticides, providing macro-and micronutrients, and secreting active but variable secondary metabolites like-phytohormones, siderophores, ACC deaminase, etc. This review critically aims to advance mechanistic understanding related to the reduction of phytotoxicity of pesticides via the use of microbe-mediated remediation techniques leading to crop optimization in pesticide-stressed soils. The literature surveyed and data presented herein are extremely useful, offering agronomists-and crop protectionists microbes-assisted remedial strategies for affordably enhancing crop productivity in pesticide-stressed soils.

Exogenous nanoselenium alleviates imidacloprid-induced oxidative stress toxicity by improving phenylpropanoid metabolism and antioxidant defense system in Perilla frutescens (L.) Britt

Few studies have been conducted to investigate the impact of pesticides on the secondary metabolism of traditional Chinese medicine and strategies to mitigate the toxicity of pesticide-induced oxidative stress. The current study focuses on evaluating the potential impacts of nano selenium (NSe) and imidacloprid (IMI) on the quality, physiological biochemistry, and secondary metabolites in Perilla frutescens (L.) Britt. (P. frutescens). The study utilized metabolome analysis to explore the toxicity mechanism of IMI. The study noted that IMI-induced stress could emerge with detrimental effects by targeting the destruction of the phenylpropanoid biosynthesis pathway. IMI-induced phenylpropanoid metabolism disorder resulted in an 8%, 17%, 25%, 10%, 65%, and 29% reduction in phenylalanine, coniferyl aldehyde, ferulic acid, cafestol, p-coumaraldehyde, and p-coumaric acid levels, respectively. Under the treatment of exogenous NSe, the levels of these metabolites were increased by 16%, 32%, 22%, 22%, 92%, and 29%, respectively. The application of exogenous NSe increased the levels of these metabolites and improved the biochemical disorder and quality of P. frutescens leaves by optimizing the phenylpropanoid metabolic pathway and enhancing the antioxidant system. Overall, the results suggest that foliar application of NSe could alleviate the oxidative stress toxicity induced by IMI and improve the quality of P. frutescens.

Tefluthrin induced toxicities in zebrafish: Focusing on enantioselectivity

Tefluthrin is one of widely used chiral pyrethroid pesticides. The potential enantioselective risk posed by tefluthrin to the aquatic ecosystem is still unclear. In this study, the toxicity differences and corresponding mechanism of tefluthrin on zebrafish were investigated at the enantiomeric level. The results indicated that two tefluthrin enantiomers showed different acute toxicity, developmental toxicity and oxidative stress to zebrafish. The acute toxicity of (1R,3R)-tefluthrin was 130-176 fold as that of (1S,3S)-tefluthrin on zebrafish embryos, larvae and adults. (1R,3R)-Tefluthrin presented approximately 10, 3 and 2 times inhibition effect on the deformity rate, hatching rate and spontaneous movements on embryos as that of (1S,3S)-tefluthrin. Meanwhile, (1R,3R)-tefluthrin caused stronger oxidative stress on zebrafish embryo than (1S,3S)-tefluthrin. The molecular docking results revealed that there were stereospecific binding affinities between tefluthrin enantimers and sodium channel protein (Nav1.6), which may lead to acute toxicity differences. Transcriptome analysis showed that the two tefluthrin enantiomers markedly disturbed differential embryonic genes expression, thereby potentially causing the chronic enantioselective toxicity. The findings of the study reveal the toxicity differences and potential mechanism of tefluthrin enantiomers on zebrafish. These results also provides a foundation for a systematic evaluation of tefluthrin at enantiomer level.

Entomopathogen-based biopesticides: insights into unraveling their potential in insect pest management

Global food security is a critical challenge to fulfill the demands of an exponentially growing population. To date, growers rely on chemicals; the broad-spectrum application of synthetic molecules leads to environmental contamination, resistance development, residual toxicity, pest resurgence, and a detrimental effect on human health and cattle. Crop production needs to be improved considering environmental and human health concerns to ensure food security. Furthermore, economically important crops are prone to attack by insect pests, causing considerable yield losses. Microbes are an eco-friendly, versatile alternative, and a potential candidate for combatting destructive pests below the economic injury level and improving the plant's health and productivity. Several microbial pathogens, including parasites, predators, parasitoids, pollinators, and many beneficial microorganisms, possess toxic properties against target organisms but do not cause harm to the non-target organisms. Entomopathogens (ENMs) have great potential for pest suppression due to their remarkable properties. Bacteria are host-specific, but fungi have a broader host range and can be significantly affected by both soil-dwelling and terrestrial insect pests. Virulent pathogens cause mortality in target insect pests known as ENMs and can penetrate through natural openings, ingestions, and integuments to cause a possible effect on target insect pests. The objective of using ENMs is to sustain productivity, improve environmental health, reduce pesticides, and conserve natural resources. Moreover, research is ongoing to discover other possible aspects, especially exploring potential ENMs. Therefore, there is a need for identification, isolation, and bioformulation to overcome the existing issues. This study is mainly focused on the status of bio-formulations, pathogenicity, their mode of action, and the potential application of different types of microbial formulations for sustainable pest management.

Microbial Diversity and Enzyme Activity as Indicators of Permethrin-Exposed Soil Health

Owing to their wide range of applications in the control of ticks and insects in horticulture, forestry, agriculture and food production, pyrethroids pose a significant threat to the environment, including a risk to human health. Hence, it is extremely important to gain a sound understanding of the response of plants and changes in the soil microbiome induced by permethrin. The purpose of this study has been to show the diversity of microorganisms, activity of soil enzymes and growth of Zea mays following the application of permethrin. This article presents the results of the identification of microorganisms with the NGS sequencing method, and of isolated colonies of microorganisms on selective microbiological substrates. Furthermore, the activity of several soil enzymes, such as dehydrogenases (Deh), urease (Ure), catalase (Cat), acid phosphatase (Pac), alkaline phosphatase (Pal), β-glucosidase (Glu) and arylsulfatase (Aryl), as well as the growth of Zea mays and its greenness indicators (SPAD), after 60 days of growth following the application of permethrin, were presented. The research results indicate that permethrin does not have a negative effect on the growth of plants. The metagenomic studies showed that the application of permethrin increases the abundance of Proteobacteria, but decreases the counts of Actinobacteria and Ascomycota. The application of permethrin raised to the highest degree the abundance of bacteria of the genera Cellulomonas, Kaistobacter, Pseudomonas, Rhodanobacter and fungi of the genera Penicillium, Humicola, Iodophanus, Meyerozyma. It has been determined that permethrin stimulates the multiplication of organotrophic bacteria and actinomycetes, decreases the counts of fungi and depresses the activity of all soil enzymes in unseeded soil. Zea mays is able to mitigate the effect of permethrin and can therefore be used as an effective phytoremediation plant.

Impact of historical legacy pesticides on achieving legislative goals in Europe

Pesticides are widely used in agriculture to optimise food production. However, the movement of pesticides into water bodies negatively impacts aquatic environments. The European Union (EU) aims to make food systems fair, healthy and environmentally friendly through its current Farm to Fork strategy. As part of this strategy, the EU plans to reduce the overall use and risk of chemical pesticides by 50 % by 2030. The attainment of this target may be compromised by the prevalence of legacy pesticides arising from historical applications to land, which can persist in the environment for several decades. The current EU Farm to Fork policy overlooks the potential challenges of legacy pesticides and requirements for their remediation. In this review, the current knowledge regarding pesticide use in Europe, as well as pathways of pesticide movement to waterways, are investigated. The issues of legacy pesticides, including exceedances, are examined, and existing and emerging methods of pesticide remediation, particularly of legacy pesticides, are discussed. The fact that some legacy pesticides can be detected in water samples, more than twenty-five years after they were prohibited, highlights the need for improved EU strategies and policies aimed at targeting legacy pesticides in order to meet future targets.

Spatial Distribution and Risk Assessment of Heavy Metal(oid)s Contamination in Topsoil around a Lead and Zinc Smelter in Henan Province, Central China

A total of 137 farmland soil samples were collected around a lead/zinc smelter within 64 km². The concentration, spatial distribution, and potential source of nine heavy metal(oid)s (As, Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) in soils and their potential ecological risk were investigated in detail. The results showed that the average concentrations of Cd, Pb, Cr and Zn in these soils were higher than their background value in Henan Province, and the average content of Cd was 2.83 times of the risk screening values in the national standard of China (GB 15618-2018). According to the distribution of different heavy metal(oid)s in soils, Cd and Pb in soil decrease gradually with the increase of distance from the smelter to the surrounding area. This indicates that the Pb and Cd originate from smelters via airborne practices according to the typical air pollution diffusion model. The distribution of Zn, Cu, and As were similar to Cd and Pb. However, Ni, V, Cr, and Co were mainly affected by soil parent materials. The potential ecological risk of Cd was higher than those of other elements, and the risk grade of the other eight elements was mainly low. The polluted soils with significantly high and high potential ecological risk covered 93.84% of all the studied regions. This should be of serious concern to government. The results of a principal component analysis (PCA) and cluster analysis (CA) show that Pb, Cd, Zn, Cu, and As were the elements mainly stemmed from smelter and other types of plants, with a contribution rate of 60.08%, while Co, Cr, Ni, and V are mainly caused by nature, with a contribution rate of 26.26%.

Metabolomics-Based Mechanistic Insights into Revealing the Adverse Effects of Pesticides on Plants: An Interactive Review

In plant biology, metabolomics is often used to quantitatively assess small molecules, metabolites, and their intermediates in plants. Metabolomics has frequently been applied to detect metabolic alterations in plants exposed to various biotic and abiotic stresses, including pesticides. The widespread use of pesticides and agrochemicals in intensive crop production systems is a serious threat to the functionality and sustainability of agroecosystems. Pesticide accumulation in soil may disrupt soil-plant relationships, thereby posing a pollution risk to agricultural output. Application of metabolomic techniques in the assessment of the biological consequences of pesticides at the molecular level has emerged as a crucial technique in exposome investigations. State-of-the-art metabolomic approaches such as GC-MS, LC-MS/MS UHPLC, UPLC-IMS-QToF, GC/EI/MS, MALDI-TOF MS, and ¹H-HR-MAS NMR, etc., investigating the harmful effects of agricultural pesticides have been reviewed. This updated review seeks to outline the key uses of metabolomics related to the evaluation of the toxicological impacts of pesticides on agronomically important crops in exposome assays as well as bench-scale studies. Overall, this review describes the potential uses of metabolomics as a method for evaluating the safety of agricultural chemicals for regulatory applications. Additionally, the most recent developments in metabolomic tools applied to pesticide toxicology and also the difficulties in utilizing this approach are discussed.

The Impact of Permethrin and Cypermethrin on Plants, Soil Enzyme Activity, and Microbial Communities

Pyrethroids are insecticides most commonly used for insect control to boost agricultural production. The aim of the present research was to determine the effect of permethrin and cypermethrin on cultured and non-cultivated bacteria and fungi and on the activity of soil enzymes, as well as to determine the usefulness of Zea mays in mitigating the adverse effects of the tested pyrethroids on the soil microbiome. The analyses were carried out in the samples of both soil not sown with any plant and soil sown with Zea mays. Permethrin and cypermethrin were found to stimulate the multiplication of cultured organotrophic bacteria (on average by 38.3%) and actinomycetes (on average by 80.2%), and to inhibit fungi growth (on average by 31.7%) and the enzymatic activity of the soil, reducing the soil biochemical fertility index (BA) by 27.7%. They also modified the number of operational taxonomic units (OTUs) of the Actinobacteria and Proteobacteria phyla and the Ascomycota and Basidiomycota phyla. The pressure of permethrin and cypermethrin was tolerated well by the bacteria Sphingomonas (clone 3214512, 1052559, 237613, 1048605) and Bacillus (clone New.ReferenceOTU111, 593219, 578257), and by the fungi Penicillium (SH1533734.08FU, SH1692798.08FU) and Trichocladium (SH1615601.08FU). Both insecticides disturbed the growth and yielding of Zea mays, as a result of which its yield and leaf greenness index decreased. The cultivation of Zea mays had a positive effect on both soil enzymes and soil microorganisms and mitigated the anomalies caused by the tested insecticides in the microbiome and activity of soil enzymes. Permethrin decreased the yield of its aerial parts by 37.9% and its roots by 33.9%, whereas respective decreases caused by cypermethrin reached 16.8% and 4.3%.

Bacterial ACC deaminase: Insights into enzymology, biochemistry, genetics, and potential role in amelioration of environmental stress in crop plants

Growth and productivity of crop plants worldwide are often adversely affected by anthropogenic and natural stresses. Both biotic and abiotic stresses may impact future food security and sustainability; global climate change will only exacerbate the threat. Nearly all stresses induce ethylene production in plants, which is detrimental to their growth and survival when present at higher concentrations. Consequently, management of ethylene production in plants is becoming an attractive option for countering the stress hormone and its effect on crop yield and productivity. In plants, ACC (1-aminocyclopropane-1-carboxylate) serves as a precursor for ethylene production. Soil microorganisms and root-associated plant growth promoting rhizobacteria (PGPR) that possess ACC deaminase activity regulate growth and development of plants under harsh environmental conditions by limiting ethylene levels in plants; this enzyme is, therefore, often designated as a "stress modulator." TheACC deaminase enzyme, encoded by the AcdS gene, is tightly controlled and regulated depending upon environmental conditions. Gene regulatory components of AcdS are made up of the LRP protein-coding regulatory gene and other regulatory components that are activated via distinct mechanisms under aerobic and anaerobic conditions. ACC deaminase-positive PGPR strains can intensively promote growth and development of crops being cultivated under abiotic stresses including salt stress, water deficit, waterlogging, temperature extremes, and presence of heavy metals, pesticides and other organic contaminants. Strategies for combating environmental stresses in plants, and improving growth by introducing the acdS gene into crop plants via bacteria, have been investigated. In the recent past, some rapid methods and cutting-edge technologies based on molecular biotechnology and omics approaches involving proteomics, transcriptomics, metagenomics, and next generation sequencing (NGS) have been proposed to reveal the variety and potential of ACC deaminase-producing PGPR that thrive under external stresses. Multiple stress-tolerant ACC deaminase-producing PGPR strains have demonstrated great promise in providing plant resistance/tolerance to various stressors and, therefore, it could be advantageous over other soil/plant microbiome that can flourish under stressed environments.