Biodegradation of the Pesticide Fenamiphos by Ten Different Species of Green Algae and Cyanobacteria

Role of Lactic Acid Bacteria in Insecticide Residue Degradation

Lactic acid bacteria are gaining global attention, especially due to their role as a probiotic. They are increasingly being used as a flavoring agent and food preservative. Besides their role in food processing, lactic acid bacteria also have a significant role in degrading insecticide residues in the environment. This review paper highlights the importance of lactic acid bacteria in degrading insecticide residues of various types, such as organochlorines, organophosphorus, synthetic pyrethroids, neonicotinoids, and diamides. The paper discusses the mechanisms employed by lactic acid bacteria to degrade these insecticides, as well as their potential applications in bioremediation. The key enzymes produced by lactic acid bacteria, such as phosphatase and esterase, play a vital role in breaking down insecticide molecules. Furthermore, the paper discusses the challenges and future directions in this field. However, more research is needed to optimize the utilization of lactic acid bacteria in insecticide residue degradation and to develop practical strategies for their implementation in real-world scenarios.

Microplastics derived from plastic mulch films and their carrier function effect on the environmental risk of pesticides

Plastic film mulching can maintain soil water and heat conditions, promote plant growth and thus generate considerable economic benefits in agriculture. However, as they age, these plastics degrade and form microplastics (MPs). Additionally, pesticides are widely utilized to control organisms that harm plants, and they can ultimately enter and remain in the environment after use. Pesticides can also be sorbed by MPs, and the sorption kinetics and isotherms explain the three stages of pesticide sorption: rapid sorption, slow sorption and sorption equilibrium. In this process, hydrophobic and partition interactions, electrostatic interactions and valence bond interactions are the main sorption mechanisms. Additionally, small MPs, biodegradable MPs and aged conventional MPs often exhibit stronger pesticide sorption capacity. As environmental conditions change, especially in simulated biological media, pesticides can desorb from MPs. The utilization of pesticides by environmental microorganisms is the main factor controlling the degradation rate of pesticides in the presence of MPs. Pesticide sorption by MPs and size effects of MPs on pesticides are related to the internal exposure level of biological pesticides and changes in pesticide toxicity in the presence of MPs. Most studies have suggested that MPs exacerbate the toxicological effects of pesticides on sentinel species. Hence, the environmental risks of pesticides are altered by MPs and the carrier function of MPs. Based on this, research on the affinity between MPs and various pesticides should be systematically conducted. During agricultural production, pesticides should be cautiously selected and used plastic film to ensure human health and ecological security.

Diversity and Functionality of Bacteria Associated with Different Tissues of Spider Heteropoda venatoria Revealed through Integration of High-Throughput Sequencing and Culturomics Approaches

Spiders host a diverse range of bacteria in their guts and other tissues, which have been found to play a significant role in their fitness. This study aimed to investigate the community diversity and functional characteristics of spider-associated bacteria in four tissues of Heteropoda venatoria using HTS of the 16S rRNA gene and culturomics technologies, as well as the functional verification of the isolated strains. The results of HTS showed that the spider-associated bacteria in different tissues belonged to 34 phyla, 72 classes, 170 orders, 277 families, and 458 genera. Bacillus was found to be the most abundant bacteria in the venom gland, silk gland, and ovary, while Stenotrophomonas, Acinetobacter, and Sphingomonas were dominant in the gut microbiota. Based on the amplicon sequencing results, 21 distinct cultivation conditions were developed using culturomics to isolate bacteria from the ovary, gut, venom gland, and silk gland. A total of 119 bacterial strains, representing 4 phyla and 25 genera, with Bacillus and Serratia as the dominant genera, were isolated. Five strains exhibited high efficiency in degrading pesticides in the in vitro experiments. Out of the 119 isolates, 28 exhibited antibacterial activity against at least one of the tested bacterial strains, including the pathogenic bacteria Staphylococcus aureus, Acinetobacter baumanii, and Enterococcus faecalis. The study also identified three strains, GL312, PL211, and PL316, which exhibited significant cytotoxicity against MGC-803. The crude extract from the fermentation broth of strain PL316 was found to effectively induce apoptosis in MGC-803 cells. Overall, this study offers a comprehensive understanding of the bacterial community structure associated with H. venatoria. It also provides valuable insights into discovering novel antitumor natural products for gastric cancer and xenobiotic-degrading bacteria of spiders.

Removal of organic and inorganic contaminants from the air, soil, and water by algae

Rapid increases in human populations and development has led to a significant exploitation of natural resources around the world. On the other hand, humans have come to terms with the consequences of their past mistakes and started to address current and future resource utilization challenges. Today's primary challenge is figuring out and implementing eco-friendly, inexpensive, and innovative solutions for conservation issues such as environmental pollution, carbon neutrality, and manufacturing effluent/wastewater treatment, along with xenobiotic contamination of the natural ecosystem. One of the most promising approaches to reduce the environmental contamination load is the utilization of algae for bioremediation. Owing to their significant biosorption capacity to deactivate hazardous chemicals, macro-/microalgae are among the primary microorganisms that can be utilized for phytoremediation as a safe method for curtailing environmental pollution. In recent years, the use of algae to overcome environmental problems has advanced technologically, such as through synthetic biology and high-throughput phenomics, which is increasing the likelihood of attaining sustainability. As the research progresses, there is a promise for a greener future and the preservation of healthy ecosystems by using algae. They might act as a valuable tool in creating new products.

Oxidative stress in Arthrospira platensis by two organophosphate pesticides

Although it is known that organophosphate insecticides are harmfull to aquatic ecosystems, oxidative damages caused by Dimethoate and Chlorpyrifos are not studied on Arthrospira platensis Gomont. In this study, various Chlorpyrifos (0-150 µg mL-1) and Dimethoate (0-250 µg mL-1) concentrations were added to the culture medium in laboratory to evaulate growth rate, chlorophyll-a content and antioxidant parameters of A. platensis. Optical Density (OD560) and chlorophyll-a decreased compared to the control for seven days in both pesticide applications. Superoxide dismutase (SOD) activity increased at 50 µg mL-1 Chlorpyrifos concentration but it decreased at all concentrations. Although Ascorbate peroxidase (APX) and glutathione reductase (GR) activities increased with Chlorpyrifos application, they did not change with Dimethoate application. Malondialdehyde (MDA) amount decreased at 150 µg mL-1 Chlorpyrifos concentration but it increased in Dimethoate application. The H2O2 content were increased in both applications. Proline decreased in 50 and 75 µg mL-1 Chlorpyrifos concentrations and increased at 150 µg mL-1 concentration, while it increased at 25 µg mL-1 Dimethoate concentration. The results were tested at 0.05 significance level. These pesticides inhibit A. platensis growth and chlorophyll-a production and cause oxidative stress. The excessive use may affect the phytoplankton and have negative consequences in the aquatic ecosystem.

Pesticide Use and Degradation Strategies: Food Safety, Challenges and Perspectives

While recognizing the gaps in pesticide regulations that impact consumer safety, public health concerns associated with pesticide contamination of foods are pointed out. The strategies and research directions proposed to prevent and/or reduce pesticide adverse effects on human health and the environment are discussed. Special attention is paid to organophosphate pesticides, as widely applied insecticides in agriculture, veterinary practices, and urban areas. Biotic and abiotic strategies for organophosphate pesticide degradation are discussed from a food safety perspective, indicating associated challenges and potential for further improvements. As food systems are endangered globally by unprecedented challenges, there is an urgent need to globally harmonize pesticide regulations and improve methodologies in the area of food safety to protect human health.

Current insights into the microbial degradation of nicosulfuron: Strains, metabolic pathways, and molecular mechanisms

Nicosulfuron is among the sulfonylurea herbicides that are widely used to control annual and perennial grass weeds in cornfields. However, nicosulfuron residues in the environment are likely to cause long-lasting harmful environmental and biological effects. Nicosulfuron degrades via photo-degradation, chemical hydrolysis, and microbial degradation. The latter is crucial for pesticide degradation and has become an essential strategy to remove nicosulfuron residues from the environment. Most previous studies have focused on the screening, degradation characteristics, and degradation pathways of biodegrader microorganisms. The isolated nicosulfuron-degrading strains include Bacillus, Pseudomonas, Klebsiella, Alcaligenes, Rhodopseudomonas, Ochrobactrum, Micrococcus, Serratia, Penicillium, Aspergillus, among others, all of which have good degradation efficiency. Two main intermediates, 2-amino-4,6-dimethoxypyrimidine (ADMP) and 2-aminosulfonyl-N,N-dimethylnicotinamide (ASDM), are produced during microbial degradation and are derived from the C-N, C-S, and S-N bond breaks on the sulfonylurea bridge, covering almost every bacterial degradation pathway. In addition, enzymes related to the degradation of nicosulfuron have been identified successively, including the manganese ABC transporter (hydrolase), Flavin-containing monooxygenase (oxidase), and E3 (esterase). Further in-depth studies based on molecular biology and genetics are needed to elaborate on their role in the evolution of novel catabolic pathways and the microbial degradation of nicosulfuron. To date, few reviews have focused on the microbial degradation and degradation mechanisms of nicosulfuron. This review summarizes recent advances in nicosulfuron degradation and comprehensively discusses the potential of nicosulfuron-degrading microorganisms for bioremediating contaminated environments, providing a reference for further research development on nicosulfuron biodegradation in the future.

The Potential of Microalgae-Bacteria Consortia to Restore Degraded Soils

Soil restoration is one of the biggest challenges of this century. Besides the negative impacts of climate change, the current increase in food demands has put severe pressure on soil resources, resulting in a significant area of degraded land worldwide. However, beneficial microorganisms, such as microalgae and plant growth-promoting bacteria, have an outstanding ability to restore soil health and fertility. In this mini-review, we summarize state-of-the-art knowledge on these microorganisms as amendments that are used to restore degraded and contaminated soils. Furthermore, the potential of microbial consortia to maximize beneficial effects on soil health and boost the production of plant-growth-promoting compounds within a mutualistic interaction is discussed.

Pesticide contamination in agro-ecosystems: toxicity, impacts, and bio-based management strategies

Continuous rise in application of pesticides in the agro-ecosystems in order to ensure food supply to the ever-growing population is of greater concern to the human health and the environment. Once entered into the agro-ecosystem, the fate and transport of pesticides is determined largely by the nature of pesticides and the soil attributes, in addition to the soil-inhabiting microbes, fauna, and flora. Changes in the soil microbiological actions, soil properties, and enzymatic activities resulting from pesticide applications are the important factors substantially affecting the soil productivity. Disturbances in the microbial community composition may lead to the considerable perturbations in cycling of major nutrients, metals, and subsequent uptake by plants. Indiscriminate applications are linked with the accumulation of pesticides in plant-based foods, feeds, and animal products. Furthermore, rapid increase in the application of pesticides having long half-life has also been reported to contaminate the nearby aquatic environments and accumulation in the plants, animals, and microbes surviving there. To circumvent the negative consequences of pesticide application, multitude of techniques falling in physical, chemical, and biological categories are presented by different investigators. In the present study, important findings pertaining to the pesticide contamination in cultivated agricultural soils; toxicity on soil microbes, plants, invertebrates, and vertebrates; effects on soil characteristics; and alleviation of toxicity by bio-based management approaches have been thoroughly reviewed. With the help of bibliometric analysis, thematic evolution and research trends on the bioremediation of pesticides in the agro-ecosystems have also been highlighted.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

Microbial Remediation: A Promising Tool for Reclamation of Contaminated Sites with Special Emphasis on Heavy Metal and Pesticide Pollution: A Review

Heavy metal and pesticide pollution have become an inevitable part of the modern industrialized environment that find their way into all ecosystems. Because of their persistent nature, recalcitrance, high toxicity and biological enrichment, metal and pesticide pollution has threatened the stability of the environment as well as the health of living beings. Due to the environmental persistence of heavy metals and pesticides, they get accumulated in the environs and consequently lead to food chain contamination. Therefore, remediation of heavy metals and pesticide contaminations needs to be addressed as a high priority. Various physico-chemical approaches have been employed for this purpose, but they have significant drawbacks such as high expenses, high labor, alteration in soil properties, disruption of native soil microflora and generation of toxic by-products. Researchers worldwide are focusing on bioremediation strategies to overcome this multifaceted problem, i.e., the removal, immobilization and detoxification of pesticides and heavy metals, in the most efficient and cost-effective ways. For a period of millions of evolutionary years, microorganisms have become resistant to intoxicants and have developed the capability to remediate heavy metal ions and pesticides, and as a result, they have helped in the restoration of the natural state of degraded environs with long term environmental benefits. Keeping in view the environmental and health concerns imposed by heavy metals and pesticides in our society, we aimed to present a generalized picture of the bioremediation capacity of microorganisms. We explore the use of bacteria, fungi, algae and genetically engineered microbes for the remediation of both metals and pesticides. This review summarizes the major detoxification pathways and bioremediation technologies; in addition to that, a brief account is given of molecular approaches such as systemic biology, gene editing and omics that have enhanced the bioremediation process and widened its microbiological techniques toward the remediation of heavy metals and pesticides.

A Review of Microalgae- and Cyanobacteria-Based Biodegradation of Organic Pollutants

This review proposes a new bioremediation method based on the diverse functionalities of algae. A greenway for cleansing wastewater is more ecologically friendly and environmentally sustainable than prior methods with other bacteria. New bioremediation technology employing algae and cyanobacteria for the removal of a wide range of organic contaminants is reasonable and has great potential. The prevalence of organic contaminants in aquatic habitats may endanger the health and well-being of several marine creatures. Agriculture, industry, and household trash are just a few of the human-caused sources of organic pollutants that contaminate waterways around the world. Before wastewater can be released into waterways, it must be cleaned. Algae-based wastewater treatment systems are becoming increasingly popular because of their environmental sustainability and lack of secondary pollutants. According to the kind of pollutant, the physicochemical properties of wastewater, and the algal species, algae and cyanobacteria can absorb and accumulate a wide spectrum of organic pollutants at different rates. In addition, phytoremediation is a cost-effective alternative to conventional treatments for degrading organic contaminants. Phycoremediationally produced algal biomass may also be an important part of the bioenergy value chain. This article focuses on microalgae and cyanobacteria species, which may remove many organic contaminants from water systems.

Recent advances in microalgae-based remediation of industrial and non-industrial wastewaters with simultaneous recovery of value-added products

The ability of microalgae to grow in a broad spectrum of wastewaters manifests great potentials for removing contaminants from effluents of industries and urban areas. Since the post-treatment microalgae biomass is also a significant source of high-value products, microalgae-based wastewater treatment is an economical and sustainable solution to wastewater management. Adding more value, the integration of microalgae with living/non-living materials looks more promising. Microalgae-based treatment technology has certain limitations like high operational costs, problematic harvesting, large land requirements, and hindrance in photosynthesis due to turbid wastewater. These challenges need to be essentially addressed to achieve enhanced wastewater remediation. This review has highlighted the potential applications of microalgae in contaminant removal from wastewaters, simultaneous resource recovery, efficient microalgae-based hybrid systems along with bottlenecks and prospects. This state-of-the-art article will edify the role of microalgae in wastewater remediation, biomass valorization for bio-based products, and present numerous possibilities in strengthening the circular bioeconomy.

Halosulfuron methyl did not have a significant effect on diversity and community of sugarcane rhizosphere microflora

Halosulfuron methyl (HM) is a new, highly active sulfonylurea herbicide that has been widely used for weed control in agricultural production. However, its potential ecological risks remain unknown. In this study, we investigated the impact of different concentrations of HM on bacterial communities in sugarcane rhizospheric soil by using 16S rRNA gene high-throughput sequencing. The half-life of HM for 130 mg/kg, 600 mg/kg, and 1300 mg/kg spraying concentrations were 6.64, 9.19, and 9.87 d, respectively. HM application did not alter the alpha or beta diversity of the soil bacterial community, whereas some microbial populations and the main microbial functional groups were significantly altered by HM exposure. The phylum Cyanobacteria and genus unclassified Chloroflexi group KD4-96 were found to be positively correlated with HM concentration in soils, indicating that they are highly involved in the biodegradation of HM in soils. Relationship analysis between soil properties and microbial communities showed that total nitrogen and total phosphorus concentration were two key factors that significantly influenced microbial community structure. To our best knowledge, this is the first microbial ecotoxicological assessment of HM in agricultural soil.

Bioremediation of water containing pesticides by microalgae: Mechanisms, methods, and prospects for future research

The application of pesticides reduces the loss of crops while simultaneously increasing crop productivity. However, the frequent use of pesticides can cause serious environmental problems due to their high accumulative and persistent nature. Recently, microalgae technology has received considerable success in the efficient treatment of pesticides pollution. In this review, the metabolic mechanisms responsible for the removal of pesticides are summarized based on previous studies. Different methods used to enhance the ability of microalgae to remove pesticides are critically evaluated. The recycling of microalgae biomass after wastewater treatment for biochar preparation and biodiesel production using the biorefinery approach is also introduced. Furthermore, we present potential future research directions to highlight the prospects of microalgae research in the removal of pesticides along with the production of value-added products.

Toxicity and Metabolic Fate of the Fungicide Carbendazim in the Typical Freshwater Diatom Navicula Species

Fungicides are frequently detected in natural water and have gained increasing attention as a result of their potential toxicity to non-target aquatic organisms. Carbendazim (CAR), a commonly used fungicide, was selected to explore its toxicity and biodegradation in a typical freshwater diatom Navicula sp. Results showed that the growth of Navicula sp. was inhibited by CAR, with a 24 h EC₅₀ value of 2.18 mg L^-1. Although the algal growth rate was recovered after 72 h of exposure, the chlorophyll a content remained significantly decreased when the concentration of CAR was above 0.5 mg L^-1. Moreover, Navicula sp. had a negative effect on the removal of CAR, and the acute toxicity by CAR was likely due to its rapid accumulation in algal cells. Mass spectrometric data revealed the transformation products of CAR from hydroxylation, methylation, decarboxylation, demethylation, and deamination in algal cultures. These results provide a better understanding of the environmental risks of CAR in water and point to the need for additional studies on the potential adverse biological effects of its intermediates.

Metabolic relation of cyanobacteria to aromatic compounds

Cyanobacteria, also known as blue-green (micro)algae, are able to sustain many types of chemical stress because of metabolic adaptations that allow them to survive and successfully compete in a variety of ecosystems, including polluted ones. As photoautotrophic bacteria, these microorganisms synthesize aromatic amino acids, which are precursors for a large variety of substances that contain aromatic ring(s) and that are naturally formed in the cells of these organisms. Hence, the transformation of aromatic secondary metabolites by cyanobacteria is the result of the possession of a suitable "enzymatic apparatus" to carry out the biosynthesis of these compounds according to cellular requirements. Another crucial aspect that should be evaluated using varied criteria is the response of cyanobacteria to the presence of extracellular aromatic compounds. Some aspects of the relationship between aromatic compounds and cyanobacteria such as the biosynthesis of aromatic compounds, the influence of aromatic compounds on these organisms and the fate of aromatic substances inside microalgal cells are presented in this paper. The search for this information has suggested that there is a lack of knowledge about the regulation of the biosynthesis of aromatic substances and about the transport of these compounds into cyanobacterial cells. These aspects are of pivotal importance with regard to the biotransformation of aromatic compounds and understanding them may be the goals of future research.

Metabolic relation of cyanobacteria to aromatic compounds

Cyanobacteria, also known as blue-green (micro)algae, are able to sustain many types of chemical stress because of metabolic adaptations that allow them to survive and successfully compete in a variety of ecosystems, including polluted ones. As photoautotrophic bacteria, these microorganisms synthesize aromatic amino acids, which are precursors for a large variety of substances that contain aromatic ring(s) and that are naturally formed in the cells of these organisms. Hence, the transformation of aromatic secondary metabolites by cyanobacteria is the result of the possession of a suitable "enzymatic apparatus" to carry out the biosynthesis of these compounds according to cellular requirements. Another crucial aspect that should be evaluated using varied criteria is the response of cyanobacteria to the presence of extracellular aromatic compounds. Some aspects of the relationship between aromatic compounds and cyanobacteria such as the biosynthesis of aromatic compounds, the influence of aromatic compounds on these organisms and the fate of aromatic substances inside microalgal cells are presented in this paper. The search for this information has suggested that there is a lack of knowledge about the regulation of the biosynthesis of aromatic substances and about the transport of these compounds into cyanobacterial cells. These aspects are of pivotal importance with regard to the biotransformation of aromatic compounds and understanding them may be the goals of future research.

Growth, photosynthesis and removal responses of the cyanobacteria Chroococcus sp. to malathion and malaoxon

Malathion is an organophosphorus pesticide widely used in agricultural crops, despite its toxicity. In addition, malaoxon occurs by oxidation of malathion being more toxic. The toxic effects of malathion and malaoxon in humans include hepatoxicity, breast cancer, genetic damage and endocrine disruption. The aim of this study involved assessing the effect of malathion commercial grade on Chroococcus sp., and its potential as an alternative to the removal of this pesticide and its transformation product such as malaoxon. We evaluated the effect of malathion at different concentrations (1, 25, 50, 75 and 100 ppm) on the biomass of the cyanobacteria Chroococcus sp. grown in medium BG-11; also, we analyse its ability to degrade both malathion and malaoxon into a temperature of 28 ± 2 °C and at pH 6. The results showed that 50 ppm of malathion the cyanobacteria Chroococcus sp. reached the highest removal efficiency of malathion and malaoxon (69 and 65%, respectively); also, the growth rate of Chroococcus sp. increased without inhibiting the production of chlorophyll "a", this can be explained by the hormesis phenomenon. Therefore, we consider that the cyanobacteria Chroococcus sp. may be a good candidate for bioremediation of aquatic systems contaminated with organophosphorus pesticides such as malathion and its transformation product such as malaoxon.

Reductive transformation of profenofos with nanoscale Fe/Ni particles

Profenofos is an abundantly used organophosphate pesticide in agriculture but its excessive use may lead to hazardous effects on environment. Thus, the present study focused on the reductive transformation of this pesticide in the presence of Fe/Ni bimetallic nanoparticles by optimizing the process parameters such as stirring time, nanoparticles dose, pH, and initial pesticide concentration. The results of reductive transformation were compared with photodegradation studies. It was found that with the increase in UV irradiation time, the percent degradation was increased. After 660 min, a 78% photodegradation of 100 μM solution of pesticide was observed. On increasing the initial pesticide concentration to 200 μM, the maximum degradation was achieved in 570 min, but here, only 73% degradation was observed. The rates of photodegradation observed with 100 to 400 μM solutions were 1.4 × 10^-3, 1.5 × 10^-3, 1.5 × 10^-3, and 5 × 10^-4 min^-1 respectively.In case of reductive transformation carried out in the presence of Fe/Ni bimetallic nanoparticles, the degradation was observed to be increased from 78 to 93.9% in only 180 min. A further increase in pesticide concentration led to a decrease in degradation. Under these conditions, the rate of reaction was found to be 1.09 × 10^-2 min^-1. A 93% degradation of profenofos was further increased to 98% when the quantity of nanoparticles was increased twice; hence, a significant reduction in time of irradiation was observed. Reductive transformation of pesticide thus provided an efficient and cheaper method for reducing the burden of profenofos from the environment.

Sorption and mobility of 14C-fenamiphos in Brazilian soils

Although fenamiphos is widely used as an insecticide and nematicide in bowling greens and agriculture, information on its sorption in tropical soils is limited. In this study, mobility, sorption, and desorption dynamics of ¹⁴C-fenamiphos in three contrasting Brazilian soils were examined both in batch and column experiments. Fenamiphos sorption coefficients (K _d ) were 2.33, 3.86, and 3.9 L kg^-1 for the three soils tested. The insecticide exhibited linear adsorption isotherms in all the three soils, and desorption was in a range of 30-40% during a 72-h period. With its low mobility, fenamiphos did not percolate through the soil profile even after 48 h. However, there is a risk of leaching to water bodies due to runoff because of its high solubility in water. In view of the fact that fenamiphos and its oxidation products are highly toxic to aquatic invertebrates and could affect the soil microbial activities even at low concentrations, the present information is of great importance in risk assessment of fenamiphos in the environment.

Degradation of tricyclazole: Effect of moisture, soil type, elevated carbon dioxide and Blue Green Algae (BGA)

Pesticide persistence and degradation in soil are influenced by factors like soil characteristics, light, moisture etc. Persistence of tricyclazole was studied under different soil moisture regimes viz., dry, field capacity and submerged in two different soil types viz., Inceptisol and Ultisol from Delhi and Karnataka, respectively. Tricyclazole dissipated faster in submerged (t1/2 160.22-177.05d) followed by field capacity (t1/2 167.17-188.07d) and dry (t1/2 300.91-334.35d) in both the soil types. Half-life of tricyclazole in Delhi field capacity soil amended with Blue Green Algae (BGA), was 150.5d as compared to 167.1d in unamended soil. In Karnataka soil amended with BGA the half-lives were 177.0d compared to 188.0d in unamended soil, indicating that BGA amendment enhanced the rate of dissipation of in both the selected soils. Tricyclazole was found to be stable in water over a pH range of 3-9, the half life in paddy field was 60.20d and 5.47d in paddy soil and paddy water, respectively. Statistical analysis and Duncan's Multiple Range Test (DMRT) revealed significant effect of moisture regime, organic matter and atmospheric CO2 level on dissipation of tricyclazole from soil and pH of water (at 95% confidence level p<0.0001).

Potential of Biological Agents in Decontamination of Agricultural Soil

Pesticides are widely used for the control of weeds, diseases, and pests of cultivated plants all over the world, mainly since the period after the Second World War. The use of pesticides is very extensive to control harm of pests all over the globe. Persistent nature of most of the synthetic pesticides causes serious environmental concerns. Decontamination of these hazardous chemicals is very essential. This review paper elaborates the potential of various biological agents in decontamination of agricultural soils. The agricultural crop fields are contaminated by the periodic applications of pesticides. Biodegradation is an ecofriendly, cost-effective, highly efficient approach compared to the physical and chemical methods which are expensive as well as unfriendly towards environment. Biodegradation is sensitive to the concentration levels of hydrogen peroxide and nitrogen along with microbial community, temperature, and pH changes. Experimental work for optimum conditions at lab scale can provide very fruitful results about specific bacterial, fungal strains. This study revealed an upper hand of bioremediation over physicochemical approaches. Further studies should be carried out to understand mechanisms of biotransformation.

In-Situ Remediation Approaches for the Management of Contaminated Sites: A Comprehensive Overview

Though several in-situ treatment methods exist to remediate polluted sites, selecting an appropriate site-specific remediation technology is challenging and is critical for successful clean up of polluted sites. Hence, a comprehensive overview of all the available remediation technologies to date is necessary to choose the right technology for an anticipated pollutant. This review has critically evaluated the (i) technological profile of existing in-situ remediation approaches for priority and emerging pollutants, (ii) recent innovative technologies for on-site pollutant remediation, and (iii) current challenges as well as future prospects for developing innovative approaches to enhance the efficacy of remediation at contaminated sites.

Ecotoxicity of two organophosphate pesticides chlorpyrifos and dichlorvos on non-targeting cyanobacteria Microcystis wesenbergii

Organophosphate pesticides (OPs), as a replacement for the organochlorine pesticides, are generally considered non-toxic to plants and algae. Chlorpyrifos and dichlorvos are two OPs used for pest control all over the world. In this study, the dose-response of cyanobacteria Microcystis wesenbergii on OPs exposure and the stimulating effect of OPs with and without phosphorus source were investigated. The results showed that high concentrations of chlorpyrifos and dichlorvos caused significant decrease of chlorophyll a content. The median inhibitory concentrations (EC50) of chlorpyrifos and dichlorvos at 96 h were 15.40 and 261.16 μmol L(-1), respectively. Growth of M. wesenbergii under low concentration of OPs (ranged from 1/10,000 to 1/20 EC50), was increased by 35.85 % (chlorpyrifos) and 41.83 % (dichlorvos) at 120 h, respectively. Correspondingly, the highest enhancement on the maximum quantum yield (F v/F m) was 4.20 % (24 h) and 9.70 % (48 h), respectively. Chlorophyll fluorescence kinetics, known as O-J-I-P transients, showed significant enhancements in the O-J, J-I, and I-P transients under low concentrations of dichlorvos at 144 h, while enhancements of chlorophyll fluorescence kinetics induced by low concentrations of chlorpyrifos were only observed in the J-I transient at 144 h. Significant decreases of chlorophyll content, F v/F m and O-J-I-P transients with OPs as sole phosphorus source were found when they were compared with inorganic phosphate treatments. The results demonstrated an evidently hormetic dose-response of M. wesenbergii to both chlorpyrifos and dichlorvos, where high dose (far beyond environmental concentrations) exposure caused growth inhibition and low dose exposure induced enhancement on physiological processes. The stimulating effect of two OPs on growth of M. wesenbergii was negligible under phosphate limitation.

Soil surface colonization by phototrophic indigenous organisms, in two contrasted soils treated by formulated maize herbicide mixtures

Soil phototrophic microorganisms, contributors to soil health and food webs, share their particular metabolism with plants. Current agricultural practices employ mixtures of pesticides to ensure the crops yields and can potentially impair these non-target organisms. However despite this environmental reality, studies dealing the susceptibility of phototrophic microorganisms to pesticide mixtures are scarce. We designed a 3 months microcosm study to assess the ecotoxicity of realistic herbicide mixtures of formulated S-metolachlor (Dual Gold Safeneur(®)), mesotrione (Callisto(®)) and nicosulfuron (Milagro(®)) on phototrophic communities of two soils (Limagne vertisol and Versailles luvisol). The soils presented different colonizing communities, with diatoms and chlorophyceae dominating communities in Limagne soil and cyanobacteria and bryophyta communities in Versailles soil. The results highlighted the strong impairment of Dual Gold Safeneur(®) treated microcosms on the biomass and the composition of both soil phototrophic communities, with no resilience after a delay of 3 months. This study also excluded any significant mixture effect on these organisms for Callisto(®) and Milagro(®) herbicides. We strongly recommend carrying on extensive soil studies on S-metolachlor and its commercial formulations, in order to reconsider its use from an ecotoxicological point of view.

Evaluation of biologically mediated changes in oil sands naphthenic acid composition by Chlamydomonas reinhardtii using negative-ion electrospray orbitrap mass spectrometry

Industrial activity associated with oil-sands extraction in Canada's Athabasca region produces a variety of contaminants of concern, including naphthenic acid fraction components (NAFCs). NAFCs are a complex mixture of organic compounds that are poorly understood both in terms of their chemical composition and effects on the environment. NAFC toxicity in the unicellular green algae Chlamydomonas reinhardtii P.A.Dangeard was correlated with the presence of the algal cell wall. It was suggested that the toxicity of NAFCs in C. reinhardtii was due to surfactant effects. Surfactant-cell wall interactions are specific and governed by the compound class and structure, and by the nature of the biological material. Here, we investigate the effects of wildtype (WT) C. reinhardtii and two cell-wall mutants on specific classes of NAFCs when growing cultures were treated with a 100 mg · L(-1) solution of NAFCs. Changes in the NAFC composition in the media were examined using high resolution mass spectrometry over a period of 4 d. Algal mediated changes in the NAFCs were limited to specific classes of NAFCs. In particular, the removal of large, classical naphthenic acids, with a double bond equivalent of 8, was observed in WT C. reinhardtii cultures. The observed algal mediated changes in NAFC composition would have been masked by low resolution mass spectrometry and highlight the importance of this tool in examining bioremediation of complex mixtures of NAFCs.

Evaluation of toxicological impact of cartap hydrochloride on some physiological activities of a non-heterocystous cyanobacterium Leptolyngbya foveolarum

The present study was aimed to the evaluation of toxicological impact of insecticide cartap hydrochloride on photosynthesis and nitrogen assimilation of a non-heterocystous cyanoprokaryote Leptolyngbya foveolarum isolated from paddy fields of Punjab, India. The microorganism tolerated commercial grade insecticide up to 80 ppm. Lower concentration (20 ppm) of cartap supported good growth with high dry weight of biomass, total protein content, photosynthetic pigments, photosynthesis and respiration compared to untreated control cultures while higher concentrations (40 and 60 ppm) inhibited these parameters in a dose dependent manner. Treatment of the microorganism with 60 ppm cartap lowered the content of photosynthetic pigments with maximum inhibitory effect on phycoerythrin (70% decrease) followed by allophycocyanin (66% decrease). Rates of photosynthesis and respiration were inhibited by 63% and 45%, respectively, while PS-I, II and whole chain activity were decreased by 45%, 67% and 40% respectively, compared to untreated control cultures. Cartap at 60 ppm decreased nitrate and nitrite uptake by 31% and 61%, respectively, whereas uptake of ammonium was slightly increased (18%) in cartap (60 ppm) treated cells. Nitrate and nitrite reductase, and glutamine synthetase activities of the microorganism decreased by 36-50% in 60 ppm cartap. The low levels of growth, photosynthetic pigments and activities of nitrogen assimilating enzymes in cells grown in nitrogen depleted medium supplement with insecticide indicated that insecticide may be used by the organism as a nitrogen source.

Anilofos tolerance and its mineralization by the cyanobacterium Synechocystis sp. strain PUPCCC 64

This study deals with anilofos tolerance and its mineralization by the common rice field cyanobacterium Synechocystis sp. strain PUPCCC 64. The organism tolerated anilofos up to 25 mg L⁻¹. The herbicide caused inhibitory effects on photosynthetic pigments of the test organism in a dose-dependent manner. The organism exhibited 60, 89, 96, 85 and 79% decrease in chlorophyll a, carotenoids, phycocyanin, allophycocyanin and phycoerythrin, respectively, in 20 mg L⁻¹ anilofos on day six. Activities of superoxide dismutase, catalase and peroxidase increased by 1.04 to 1.80 times over control cultures in presence of 20 mg L⁻¹ anilofos. Glutathione content decreased by 26% while proline content was unaffected by 20 mg L⁻¹ anilofos. The test organism showed intracellular uptake and metabolized the herbicide. Uptake of herbicide by test organism was fast during initial six hours followed by slow uptake until 120 hours. The organism exhibited maximum anilofos removal at 100 mg protein L⁻¹, pH 8.0 and 30°C. Its growth in phosphate deficient basal medium in the presence of anilofos (2.5 mg L⁻¹) indicated that herbicide was used by the strain PUPCCC 64 as a source of phosphate.

Dose-dependent effects of the herbicide mesotrione on soil cyanobacterial communities

This study aimed to investigate the dose-response effects of an herbicide on soil photosynthetic microbial communities, particularly cyanobacteria, using a microcosm approach. Pure mesotrione (active ingredient), and Callisto (a commercial formulation of this triketone herbicide), were spread at different rates on soil microcosm surfaces. Soil Chlorophyll concentrations were quantified to assess the photosynthetic biomass, and the genetic structure and diversity of the cyanobacterial community were investigated by a group-specific polymerase chain reaction followed by denaturing gradient gel electrophoresis. Dose-dependent responses were evidenced for both functional and structural parameters. No effect was detected in soils treated with 1 × AR (1-fold recommended application rate) irrespective of the herbicide formulation. At 10 × AR (10-fold recommended application rate), only Callisto treatment induced significant decreases of photosynthetic biomass, whereas structural parameters were less affected. At the 100 × AR (100-fold recommended application rate), both pure mesotrione and Callisto had strong negative impacts on soil chlorophyll concentrations and cyanobacterial genetic structure and diversity. At both the 10 × AR and 100 × AR treatments, Callisto induced significant stronger effects than pure mesotrione. In addition, indicators of photosynthetic biomass, compared with structural parameters of cyanobacterial communities (within 14 days), responded (within 7 days) more quickly to herbicide stress. The results of this study underscore the relevance of soil photosynthetic microbial communities to develop indicators for herbicide risk assessment.

Assessing the metabolic potential of phototrophic communities in surface water environments: fludioxonil as a model compound

Differences are often apparent in the observed rates of degradation between laboratory water-sediment studies and outdoor studies in surface water environments. Indeed, previous work has shown that including phototrophic communities in laboratory systems can result in the enhancement of degradation, when compared against systems that exclude phototrophs, incubated in darkness. In phototroph-inclusive systems, a range of metabolic processes and community effects are absent in the standard laboratory systems: metabolism by macrophytes, algae, and periphyton, as well as enhancement of bacterial and fungal communities by macrophyte root structures, algal biofilms, and planktonic algae. Here, the authors demonstrate the metabolic capability of algae and macrophytes in isolation from bacterial and fungal communities. The authors have isolated subcommunities and individual species from complex, phototroph-inclusive test systems, and demonstrated significant degradation of the fungicide fludioxonil in their presence. They have also shown the intrinsic metabolic competence of Elodea canadensis as well as algae from three phyla (Chlorophyta, Cyanophyta, and Bacillariophyta [diatoms]), demonstrating that phototrophic communities have the potential to play a direct role in metabolism in surface water environments. Thus, it seems that current laboratory test systems are failing to consider the role of active, competent organisms that are likely to be involved in the degradation of crop protection products in surface water environments.

Removal of 17α-ethinylestradiol from a sterile WC medium by the cyanobacteria Microcystis novacekii

An unprecedented investigation dealing with the removal of 17α-ethinylestradiol (EE2, a contraceptive hormone) by the cyanobacteria Microcystis novacekii (a species that is abundant and easily accessible in Brazilian lakes) from a sterile WC medium is described herein. The results indicated that whereas EE2 experienced insignificant spontaneous degradation, Microcystis novacekii was capable of removing ca. 65% of the hormone from the culture medium. Furthermore, no metabolites were detected at the concentration levels evaluated (0.10 to 0.17 mg L(-1)) as verified by the use of GC-MS, a quite sensitive analytical technique, and adequate pre-concentration procedures (SPME and liquid extraction). Elucidative experiments, including an appropriate cell lyses procedure, indicated that EE2 was likely accumulated within the cells (bioaccumulation) rather than adsorbed on the cellular membrane (biosorption). Moreover, the intra- and extracellular contents of EE2 were shown to be roughly complementary. Finally, the species was found to be highly tolerant to the hormone as its growth rates were higher in the test than in the control experiments. All these findings, therefore, point to the use of Microcystis novacekii as a potential agent to treat effluents contaminated with EE2.

Chlorpyrifos degradation by the cyanobacterium Synechocystis sp. strain PUPCCC 64

BACKGROUND, AIM, AND SCOPE

Indiscriminate use of insecticides leads to environmental problems and poses a great threat to beneficial microorganisms. The aim of the present work was to study chlorpyrifos degradation by a rice field cyanobacterium Synechocystis sp. strain PUPCCC 64 so that the organism is able to reduce insecticide pollution in situ.

MATERIAL AND METHODS

The unicellular cyanobacterium isolated and purified from a rice field was identified by partial 16S rRNA gene sequence as Synechocystis sp. strain PUPCCC 64. Tolerance limit of the organism was determined by studying its growth in graded concentrations (2.5-20 mg/L) of chlorpyrifos. Chlorpyrifos removal was studied by its depletion from the insecticide supplemented growth medium, and its biodegradation products were identified in the cell extract, biomass wash, and growth medium.

RESULTS AND DISCUSSION

The organism tolerated chlorpyrifos up to 15 mg/L. Major fraction of chlorpyrifos was removed by the organism during the first day followed by slow uptake. Biomass, pH, and temperature influenced the insecticide removal and the organism exhibited maximum chlorpyrifos removal at 100 mg protein/L biomass, pH 7.0, and 30°C. The cyanobacterium metabolized chlorpyrifos producing a number of degradation products as evidenced by GC-MS chromatogram. One of the degradation products was identified as 3,5,6-trichloro-2-pyridinol.

CONCLUSION AND RECOMMENDATIONS

Present study reports the biodegradation of chlorpyrifos by Synechocystis sp. Biodegradation of the insecticide by the cyanobacterium is significant as it can be biologically removed from the environment. The cyanobacterium may be used for bioremediation of chlorpyrifos-contaminated soils.

Assessing lethal and sub-lethal effects of trichlorfon on different trophic levels

Trichlorfon (TCF) is one of the most used veterinary pharmaceuticals not only to fight infestations but also as a preventive measure worldwide. The high concentrations used generate concerns about environmental and human health. In this work we assessed the acute toxicity of this compound to non-target organisms belonging to different trophic levels: Danio rerio (early life stages and adults), Daphnia magna and algae (Pseudokirchneriella subcapitata and Chlorella vulgaris), and studied the potential of the biomarkers cholinesterase (ChE), glutathione-S-transferase (GST), lactate dehydrogenase (LDH) and catalase (CAT) to assess sub-lethal effects of trichlorfon in zebrafish and daphnids. The fish embryo test followed the OECD draft guideline FET and was based on the exposure of newly fertilized eggs to 0, 2.5, 5.0, 10, 20, 40, 80 and 160 mg/L of TCF for 5 days; the fish acute test followed the OECD guideline 203 and was based on the exposure of adult fish to 0, 2.5, 5, 10, 20, 40, 60 and 80 mg/L of TCF for 4 days; Daphnia sp. immobilization assay followed the OECD guideline 202 and was based on the exposure of juvenile daphnids to 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1 and 2 μg/L of TCF for 2 days and the algae growth inhibition assay followed the OECD guideline 201 and was based on the exposure of the two species to 0, 1, 3.2, 10, 32, 100 and 300 mg/L of TCF for 4 days. Biomarker levels were measured after 96 h exposure to TCF in zebrafish early life stages and adults and after 48 h exposure in D. magna. Tested organisms seem to have dissimilar sensitivities towards TCF exposure. D. magna (48 h-LC(50)=0.29 μg/L) was the most sensitive organism, followed by early life stages and adults of zebrafish (96 h-LC(50)=25.4 and 28.8 mg/L, respectively) and finally by the algae P. subcapitata (96 h-LC(50)=274.5 mg/L) and C. vulgaris (no effect observed). As daphnids are a source of food for organisms of higher trophic levels, the impairment on its population is prone to have consequences in the entire ecosystem. The biomarker activities measured in daphnids and fish seemed to be useful tools in the assessment of trichlorfon effects, especially ChE activity which was the most sensitive biomarker tested for all organisms. Trichlorfon was teratogenic for zebrafish embryos leading to anomalies in the absorption of the yolk sac, spine bending and pericardial oedemas. The present research suggests that further work is urgently needed in order to monitor environmental concentrations of trichlorfon and to test the long term effects of environmentally realistic concentrations of this compound.

Assessing the potential for algae and macrophytes to degrade crop protection products in aquatic ecosystems

Rates of pesticide degradation in aquatic ecosystems often differ between those observed within laboratory studies and field trials. Under field conditions, a number of additional processes may well have a significant role, yet are excluded from standard laboratory studies, for example, metabolism by aquatic plants, phytoplankton, and periphyton. These constituents of natural aquatic ecosystems have been shown to be capable of metabolizing a range of crop protection products. Here we report the rate of degradation of six crop protection products assessed in parallel in three systems, under reproducible, defined laboratory conditions, designed to compare aquatic sediment systems which exclude macrophytes and algae against those in which macrophytes and/or algae are included. All three systems remained as close as possible to the Organisation for Economic Co-operation and Development (OECD) 308 guidelines, assessing degradation of parent compound in the total system in mass balanced studies using ((14) C) labeled compounds. We observed, in all cases where estimated, significant increases in the rate of degradation in both the algae and macrophyte systems when compared to the standard systems. By assessing total system degradation within closed, mass balanced studies, we have shown that rates of degradation are enhanced in water/sediment systems that include macrophytes and algae. The contribution of these communities should therefore be considered if the aquatic fate of pesticides is to be fully understood.

Fenamiphos and related organophosphorus pesticides: environmental fate and toxicology

In this review, we emphasize recent research on the fate, transport, and metabolism of tree selected organophosphorus pesticides (fenamiphos, isofenphos, and coumaphos) in soil an water environments. This review is also concerned with the side effects of these pesticides on nontarget organisms. Despite the fact that fenamiphos is not very mobile, its oxides have been detected in the groundwaters of Western Australia. Most organophosphorus pesticides generally are chemically unstable and underfo microbial degradation in soil and water environments. Enhanced biodegradation of many organophosphorus pesticides upon their repeted applications to soil and water is well established. Myriads of soil microorganisms, bacteria in particular, exhibit an exceptional capacity to transform many organophosphorus pesticides. Fenamiphos can undergo rapid microbially mediated degradation via oxidation to its oxides (sulfoxide and sulfone) and eventually to CO2 and water in soils, or via hydrolysis, in cultures of the soil bacterium, Brevinbacterium sp. There is evidence for enhanced biodegradation of (i) isofenphos in soils with a long history of use and (ii) coumaphos in cattle dip by bacterial cultures to chlorferon and diethylthiophosphoric acid.