Complete genome sequence of Arthrobacter sp. ZXY-2 associated with effective atrazine degradation and salt adaptation

Advances in understanding and mitigating Atrazine's environmental and health impact: A comprehensive review

Atrazine is a widely used herbicide in agriculture, and it has garnered significant attention because of its potential risks to the environment and human health. The extensive utilization of atrazine, alongside its persistence in water and soil, underscores the critical need to develop safe and efficient removal strategies. This comprehensive review aims to spotlight atrazine's potential impact on ecosystems and public health, particularly its enduring presence in soil, water, and plants. As a known toxic endocrine disruptor, atrazine poses environmental and health risks. The review navigates through innovative removal techniques across soil and water environments, elucidating microbial degradation, phytoremediation, and advanced methodologies such as electrokinetic-assisted phytoremediation (EKPR) and photocatalysis. The review notably emphasizes the complex process of atrazine degradation and ongoing scientific efforts to address this, recognizing its potential risks to both the environment and human health.

The Roles of Plant-Growth-Promoting Rhizobacteria (PGPR)-Based Biostimulants for Agricultural Production Systems

The application of biostimulants has been proven to be an advantageous tool and an appropriate form of management towards the effective use of natural resources, food security, and the beneficial effects on plant growth and yield. Plant-growth-promoting rhizobacteria (PGPR) are microbes connected with plant roots that can increase plant growth by different methods such as producing plant hormones and molecules to improve plant growth or providing increased mineral nutrition. They can colonize all ecological niches of roots to all stages of crop development, and they can affect plant growth and development directly by modulating plant hormone levels and enhancing nutrient acquisition such as of potassium, phosphorus, nitrogen, and essential minerals, or indirectly via reducing the inhibitory impacts of different pathogens in the forms of biocontrol parameters. Many plant-associated species such as Pseudomonas, Acinetobacter, Streptomyces, Serratia, Arthrobacter, and Rhodococcus can increase plant growth by improving plant disease resistance, synthesizing growth-stimulating plant hormones, and suppressing pathogenic microorganisms. The application of biostimulants is both an environmentally friendly practice and a promising method that can enhance the sustainability of horticultural and agricultural production systems as well as promote the quantity and quality of foods. They can also reduce the global dependence on hazardous agricultural chemicals. Science Direct, Google Scholar, Springer Link, CAB Direct, Scopus, Springer Link, Taylor and Francis, Web of Science, and Wiley Online Library were checked, and the search was conducted on all manuscript sections in accordance with the terms Acinetobacter, Arthrobacter, Enterobacter, Ochrobactrum, Pseudomonas, Rhodococcus, Serratia, Streptomyces, Biostimulants, Plant growth promoting rhizobactera, and Stenotrophomonas. The aim of this manuscript is to survey the effects of plant-growth-promoting rhizobacteria by presenting case studies and successful paradigms in various agricultural and horticultural crops.

Treatment of atrazine-containing wastewater by algae-bacteria consortia: Signal transmission and metabolic mechanism

Atrazine is a toxic endocrine disruptor. Biological treatment methods are considered to be effective. In the present study, a modified version of the algae-bacteria consortia (ABC) was established and a control was simultaneously set up to investigate the synergistic relationship between bacteria and algae and the mechanism by which atrazine is metabolized by those microorganisms. The total nitrogen (TN) removal efficiency of the ABC reached 89.24% and the atrazine concentration was reduced to below the level recommended by the Environment Protection Agency (EPA) regulatory standards within 25 days. The protein signal released from the extracellular polymeric substances (EPS) secreted by the microorganisms triggered the resistance mechanism of the algae, and the conversion of humic acid to fulvic acid and electron transfer constituted the synergistic mechanism between the bacteria and algae. The mechanism by which atrazine is metabolized by the ABC mainly consists of hydrogen bonding, H-pi interactions, and cation exchange with atzA for hydrolysis, followed by a reaction with atzC for decomposition to non-toxic cyanuric acid. Proteobacteria was the dominant phylum for bacterial community evolution under atrazine stress, and the analysis revealed that the removal of atrazine within the ABC was mainly dependent on the proportion of Proteobacteria and the expression of degradation genes (p < 0.01). EPS played a major role in the removal of atrazine within the single bacteria group (p < 0.01).

Deciphering the recent trends in pesticide bioremediation using genome editing and multi-omics approaches: a review

Pesticide pollution in recent times has emerged as a grave environmental problem contaminating both aquatic and terrestrial ecosystems owing to their widespread use. Bioremediation using gene editing and system biology could be developed as an eco-friendly and proficient tool to remediate pesticide-contaminated sites due to its advantages and greater public acceptance over the physical and chemical methods. However, it is indispensable to understand the different aspects associated with microbial metabolism and their physiology for efficient pesticide remediation. Therefore, this review paper analyses the different gene editing tools and multi-omics methods in microbes to produce relevant evidence regarding genes, proteins and metabolites associated with pesticide remediation and the approaches to contend against pesticide-induced stress. We systematically discussed and analyzed the recent reports (2015-2022) on multi-omics methods for pesticide degradation to elucidate the mechanisms and the recent advances associated with the behaviour of microbes under diverse environmental conditions. This study envisages that CRISPR-Cas, ZFN and TALEN as gene editing tools utilizing Pseudomonas, Escherichia coli and Achromobacter sp. can be employed for remediation of chlorpyrifos, parathion-methyl, carbaryl, triphenyltin and triazophos by creating gRNA for expressing specific genes for the bioremediation. Similarly, systems biology accompanying multi-omics tactics revealed that microbial strains from Paenibacillus, Pseudomonas putida, Burkholderia cenocepacia, Rhodococcus sp. and Pencillium oxalicum are capable of degrading deltamethrin, p-nitrophenol, chlorimuron-ethyl and nicosulfuron. This review lends notable insights into the research gaps and provides potential solutions for pesticide remediation by using different microbe-assisted technologies. The inferences drawn from the current study will help researchers, ecologists, and decision-makers gain comprehensive knowledge of value and application of systems biology and gene editing in bioremediation assessments.

Immobilization of bacterial mixture of Klebsiella variicola FH-1 and Arthrobacter sp. NJ-1 enhances the bioremediation of atrazine-polluted soil environments

In this study, the effects of the immobilized bacterial mixture (IM-FN) of Arthrobacter sp. NJ-1 and Klebsiella variicola strain FH-1 using sodium alginate-CaCl₂ on the degradation of atrazine were investigated. The results showed that the optimal ratio of three types of carrier materials (i.e., rice straw powder, rice husk, and wheat bran) was 1:1:1 with the highest adsorption capacity for atrazine (i.e., 3774.47 mg/kg) obtained at 30°C. On day 9, the degradation efficiency of atrazine (50 mg/L) reached 98.23% with cell concentration of 1.6 × 10⁸  cfu/ml at pH 9 and 30°C. The Box-Behnken method was used to further optimize the culture conditions for the degradation of atrazine by the immobilized bacterial mixture. The IM-FN could be reused for 2-3 times with the degradation efficiency of atrazine maintained at 73.0% after being stored for 80 days at 25°C. The population dynamics of IM-FN was explored with the total soil DNA samples specifically analyzed by real-time PCR. In 7 days, the copy numbers of both PydC and estD genes in the IM-FN were significantly higher than those of bacterial suspensions in the soil. Compared with bacterial suspensions, the IM-FN significantly accelerated the degradation of atrazine (20 mg/kg) in soil with the half-life shortened from 19.80 to 7.96 days. The plant heights of two atrazine-sensitive crops (wheat and soybean) were increased by 14.99 and 64.74%, respectively, in the soil restored by immobilized bacterial mixture, indicating that the IM-FN significantly reduced the phytotoxicity of atrazine on the plants. Our study evidently demonstrated that the IM-FN could significantly increase the degradation of atrazine, providing a potentially effective bioremediation technique for the treatment of atrazine-polluted soil environment and providing experimental support for the wide application of immobilized microorganism technology in agriculture.

Remediation of organic amendments on soil salinization: Focusing on the relationship between soil salts and microbial communities

Soil salinization has emerged as a major factor with an adverse influence on agricultural green development worldwide. It is necessary to develop high-efficiency and ecologically beneficial management measures for alleviating soil salinization. The experiment of application for cow manure (CM), biochar (BC), and bio-organic fertilizer (BIO) in soil with light salinity was conducted to investigate the remediation of organic materials on soil salinization with melon (Cucumis melo L.) by reducing the availability of saline ions and shifting the soil microbial community. Results showed that BC treatment significantly decreased the EC values of the soil and soil solution by 19.23% and 27.02% and the concentrations of Na⁺, K⁺, and Cl^- by 13.28%, 13.08%, and 15.21%, respectively, followed by CM and BIO treatments. High-throughput sequencing identified that organic amendments significantly improved the richness of the soil bacterial community and increased the relative abundances of Acidobacteria and Firmicutes by 33.11% and 111.2%, respectively, and the beneficial salt-tolerant bacterial genera Flavobacterium, Bacillus and Arthrobacter by 32.04%, 38.92% and 35.67%, respectively. Additionally, soil Na⁺, Ca²⁺, K⁺ and Cl^- were significantly negatively correlated with Acidobacteria and Flavobacterium and were also the most important factors driving the changes in the structure of the soil bacterial communities. The bacterial networks were more complex in the organic amendments treatments than in CK, reflecting through more nodes and links and a higher average clustering coefficient, density and modularity. This study provided a comprehensive understanding of the application of organic amendments in alleviating soil salinization and improving soil bacterial and fungal communities and provides scientific support for agriculture green development.

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.

Soil bacterial community dynamics following bioaugmentation with Paenarthrobacter sp. W11 in atrazine-contaminated soil

Atrazine is one of the most widely used herbicides, however it and its metabolites cause widespread contamination in soil and ground water. Bioaugmentation is an effective method for remediation of environmental organic pollutants. High-throughput sequencing provides an important tool for understanding the changes of microbial community and function in response to pollutants degradation based on bioaugmentation. In this study, the effect of biodegradation with Paenarthrobacter sp. W11 and the change of microbial community during atrazine degradation were investigated. The results showed that bioaugmentation significantly accelerated the degradation rate of atrazine in soil and reduced the toxic effect of atrazine residues on wheat growth. The extra available NH₄⁺ through atrazine mineralization could serve as a nitrogen source to increase microbial numbers. High-throughput sequencing further revealed that the microbial community restored a new balance. The function of microbial community predicted by PICRUSt2 suggested that the biodegradation process of atrazine affected not only the atrazine degradation pathway, but also the nitrogen metabolism pathway. Methylobacillus and Pseudomonas were considered as the most important indigenous atrazine-degrading microorganisms, because their relative abundances were positively correlated with the relative abundance of Paenarthrobacter and atrazine degradation pathway. This study provides insight into the cooperation between indigenous microorganisms and external inoculums on atrazine degradation process.

Genomic insights into the antibiotic resistance pattern of the tetracycline-degrading bacterium, Arthrobacter nicotianae OTC-16

Although many bacteria have the potential to remove antibiotic residues from environmental niches, the benefits of using antibiotic-degrading bacteria to manage antibiotic pollution should be assessed against the risk of the potential expansion of antimicrobial resistance. This study investigated the antibiotic resistance pattern of the bacterium Arthrobacter nicotianae OTC-16, which shows substantial biodegradation of oxytetracycline (OTC)/tetracycline. The results showed that this strain could be resistant to at least seven categories of 15 antibiotics, based on antimicrobial susceptibility testing. The genome of A. nicotianae OTC-16 contains one chromosome (3,643,989 bp) and two plasmids (plasmid1, 123,894 bp and plasmid2, 29,841 bp). Of the 3,561 genes isolated, eight were related to antibiotic resistance. During OTC degradation by the strain OTC-16, the expression of ant2ia, sul1, tet33, and cml_e8 in the plasmid, and one gene (tetV) in the chromosome were tracked using real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Only the plasmid-derived resistance genes were up-regulated in the presence of OTC. The presence of OTC increased the tolerance of strain OTC-16 to streptomycin sulphate. The findings of this study can help deepen our understanding of the behavioural characteristics of resistance genes and adaptive evolution of drug-resistant bacteria.

Isolation and Identification of Pseudomonas sp. Strain DY-1 from Agricultural Soil and Its Degradation Effect on Prometryne

Prometryne is a widely used herbicide in China to control annual grasses and broadleaf weeds. However, the stability of prometryne makes it difficult to be degraded, which poses a threat to human health. This study presents a bacterial strain isolated from soil samples with a prometryne application history, designated strain DY-1. Strain DY-1, identified as Pseudomonas sp., is capable of utilizing prometryne as a sole carbon source for growth and degrading 100% of prometryne within 48 h from an initial concentration of 50 mg L^-1. To further optimize the degradation of prometryne, the prometryne concentration, temperature, pH, and salt concentration were examined. The optimal conditions for degradation of prometryne by strain DY-1 were an initial prometryne concentration of 50 mg L^-1, 30 °C, pH 7-8, and NaCl concentration of 200 mg L^-1. The same strain also degraded other s-triazine herbicides, including simetryne, ametryne, desmetryne, and metribuzin, under the same conditions. The biodegradation pathway of prometryne was established by isolating sulfoxide prometryne as the first metabolite and by the identification of sulfone prometryne and 2-hydroxy prometryne by liquid chromatography-mass spectrometry (LC-MS/MS). The results illustrated that strain DY-1 achieved the removal of prometryne by gradually oxidizing and hydrolyzing the methylthio groups. A bioremediation trial with contaminated soil and pot experiments showed that after treating the prometryne-contaminated soil with strain DY-1, the content of prometryne was significantly reduced (P < 0.05). This study provides an efficient bacterial strain and approach that could be potentially useful for detoxification and bioremediation of prometryne analogs.

Analysis of microbial community structure and diversity in surrounding rock soil of different waste dump sites in fushun western opencast mine

It is importance to understand the correlation between the physicochemical properties of different surrounding rock soil and microbial communities in Fushun western opencast mining for the ecological restoration of land after mine closure. In this study, two layers of soil samples were collected from four different areas in Fushun western opencast mining: coal gangue area (CGA), green mudstone area (GMA), oil shale area (OSA) and mixed area (MA). Then, the effects of different surrounding rock soil physicochemical properties on the microbial communities were explored using the High-throughput sequencing technique. A wide diversity of taxonomical groups were present in four soil cores, and many were correlated with soil physicochemical properties. The obvious differences in microbial communities between different areas showed the influence of different surrounding rock soil on the microbial communities were significant. Redundancy analysis and the network diagram confirmed that soil physicochemical properties pH (Pondus Hydrogenii)-AN (Available Nitrogen)-EC (Electronic Conductivity)-WC (Water Content)-TK (Total Nitrogen), Cd (Cadmium)-Ni (Nickel) had great influence on the microbial communities. Therefore, this study can provide scientific judgments for the different surrounding rock soil physicochemical properties in coal mining, microbial-mediated rock mineralization and biogeochemical cycles.

Recent Advanced Technologies for the Characterization of Xenobiotic-Degrading Microorganisms and Microbial Communities

Global environmental contamination with a complex mixture of xenobiotics has become a major environmental issue worldwide. Many xenobiotic compounds severely impact the environment due to their high toxicity, prolonged persistence, and limited biodegradability. Microbial-assisted degradation of xenobiotic compounds is considered to be the most effective and beneficial approach. Microorganisms have remarkable catabolic potential, with genes, enzymes, and degradation pathways implicated in the process of biodegradation. A number of microbes, including Alcaligenes, Cellulosimicrobium, Microbacterium, Micrococcus, Methanospirillum, Aeromonas, Sphingobium, Flavobacterium, Rhodococcus, Aspergillus, Penecillium, Trichoderma, Streptomyces, Rhodotorula, Candida, and Aureobasidium, have been isolated and characterized, and have shown exceptional biodegradation potential for a variety of xenobiotic contaminants from soil/water environments. Microorganisms potentially utilize xenobiotic contaminants as carbon or nitrogen sources to sustain their growth and metabolic activities. Diverse microbial populations survive in harsh contaminated environments, exhibiting a significant biodegradation potential to degrade and transform pollutants. However, the study of such microbial populations requires a more advanced and multifaceted approach. Currently, multiple advanced approaches, including metagenomics, proteomics, transcriptomics, and metabolomics, are successfully employed for the characterization of pollutant-degrading microorganisms, their metabolic machinery, novel proteins, and catabolic genes involved in the degradation process. These technologies are highly sophisticated, and efficient for obtaining information about the genetic diversity and community structures of microorganisms. Advanced molecular technologies used for the characterization of complex microbial communities give an in-depth understanding of their structural and functional aspects, and help to resolve issues related to the biodegradation potential of microorganisms. This review article discusses the biodegradation potential of microorganisms and provides insights into recent advances and omics approaches employed for the specific characterization of xenobiotic-degrading microorganisms from contaminated environments.

Degradation of tetracycline antibiotics by Arthrobacter nicotianae OTC-16

Microbial degradation is an important option for combating antibiotic pollution. Arthrobacter nicotianae OTC-16 was isolated as a novel tetracycline-degrading bacterium, which could degrade oxytetracycline/tetracycline (OTC/TET). Toxicity assessment indicated that this bacterium effectively converted OTC into byproducts with less toxicity to bacterial and algal indicators. Six degradation products of OTC were tentatively identified, and a potential biotransformation pathway was proposed that includes decarbonylation, reduction, and dehydration. Bioaugmentation of TC removal with this bacterium was further studied in various matrices. In aqueous media, strain OTC-16 accelerated OTC removal over a temperature range of 20-35 ℃, pH range of 6.0-9.0, and OTC concentration range of 25-150 mg L^-1. The strain also facilitated the decrease of OTC and TET concentrations in both swine and chicken manures, with a maximum decrease of 91.54%, and increased the degradation of OTC in soils by 8.22-45.45%. A unique advantage of this bacterium in promoting OTC degradation in alkaline environments was demonstrated, where it successfully competed with the indigenous microbiota and largely decreased the relative abundances of the studied tetracycline resistance genes (tetB and tetW) in soil. This work offers a better understanding of the antibiotic bioaugmentation and new microbial sources.

Preparation, Performances and Mechanisms of Co@AC Composite for Herbicide Atrazine Removal in Water

In this study, a high-performance adsorbent Co@AC was prepared by loading cobalt ions (Co2+) on activated carbon (AC) via solution impregnation and high-temperature calcination technology, and was used to remove atrazine in water. The preparation factors on the adsorbent properties were studied, and the characteristics were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrometer (FTIR). The results showed that Co@AC possessed the best performance when the factors were 7.0% of Co2+ (w/v), 7.0 h of immersing time, 500 °C of calcination temperature and 4.0 h of calcination time. The adsorption conditions and mechanisms for atrazine removal by Co@AC were also studied scientifically. As the conditions were pH 4.0, reaction time 90 min and temperature 25 °C, Co@AC had the largest adsorption capacity, which was 92.95 mg/g, and the maximum removal rate reached 94.79%. The correlation coefficient of the Freundlich isotherm was better than that of the Langmuir isotherm, and the adsorption process followed the pseudo-second-order kinetic model. Cycle experiments showed that the removal efficiency of atrazine by Co@AC remained above 85% after five repeated experiments, indicating that Co@AC showed a strong stable performance and is a promising material for pesticides removal.

Effects of the long-term application of atrazine on soil enzyme activity and bacterial community structure in farmlands in China

Atrazine has been used on Chinese farmlands for a long time and over a wide range. The concentration of atrazine (1.86-1100 mg kg^-1) has exceeded the allowable limit in the soil (1.0 mg kg^-1), and concern is increasing about the potential harm to farmland soil. Four treatments (AT₀, AT₆, AT₁₀, AT₁₆) were established to reveal the effects of the long-term application of atrazine on soil health. The results showed a nonlinear regulation of the atrazine residue concentrations in the four treatments. The highest concentration of atrazine residue was in AT₆, at 167 mg kg^-1, and the lowest concentration of atrazine residue was in AT₁₆, at 102 mg kg^-1, but there was no significant difference between AT₁₀ and AT₁₆. The soil urease activity decreased significantly with the increase in the years of atrazine application, the saccharase and cellulase activities in the AT₆ were significantly higher than those observed in the other three treatments, the catalase activity gradually decreased with the increase in atrazine application years, and the activity in AT₆ was significantly higher than that in AT₁₆. A total of 238 genera were identified by Illumina MiSeq sequencing, and 28 dominant genera were screened. Atrazine significantly increased the relative abundance of Actinobacteria and contributed to the relative abundance of Rubrobacter, Blastococcus, Promicromonospora, Jiangella, Psychroglaciecola and Acetobacteraceae_uncultured, which exhibited significantly higher abundance in AT₁₆ than in AT₀. Although there were atrazine-degrading bacteria in the soil, and the atrazine residue decreased with the increase in application years, the concentration of the atrazine residue was still nearly 100 times higher than the allowable limit in the soil, which is a great threat to the soil health.

A bio-functions integration microcosm: Self-immobilized biochar-pellets combined with two strains of bacteria to remove atrazine in water and mechanisms

A self-immobilization method for microorganisms was developed based on fungal pellets. Generally, pellets have some problems such as cell leakage, cell loading limitation and low mechanical strength. Therefore, biochar was applied to overcome these disadvantages. Atrazine degradable microorganism Arthrobacter sp. ZXY-2 was immobilized by Aspergillus niger Y3 pellets. After adding biochar with optimal dosage (0.006 g biochar for 0.3 g pellets with ZXY-2), the self-immobilized biomixture (SIB) removed 50 mg /L atrazine rapidly within 1 h, which was 61% higher compared to pellets without biochar. The kinetic adsorption results showed that the biosorption of biochar by pellets followed a pseudo-second-order kinetic model. The ATZ removal ability and reusability of SIB were significantly increased by biochar. The results showed that the addition of biochar could enhance the connection between ZXY-2 and pellets based carrier, and the favorable biodegradation pH of ZXY-2 changed to 6 and 10. Several analyses such as ζ-potential measurements, FTIR, XPS, SEM-EDS, and elemental analyses were performed to evaluate the mechanism of action of SIB. To enhance the ATZ degradation by single strain, Agrobacterium, sp WL-1 was isolated and added. The metabolic pathways and their function complementation were studied. Furthermore, a biomass integration model for wastewater treatment was proposed herein.

Bacterial catabolism of s-triazine herbicides: biochemistry, evolution and application

The synthetic s-triazines are abundant, nitrogen-rich, heteroaromatic compounds used in a multitude of applications including, herbicides, plastics and polymers, and explosives. Their presence in the environment has led to the evolution of bacterial catabolic pathways in bacteria that allow use of these anthropogenic chemicals as a nitrogen source that supports growth. Herbicidal s-triazines have been used since the mid-twentieth century and are among the most heavily used herbicides in the world, despite being withdrawn from use in some areas due to concern about their safety and environmental impact. Bacterial catabolism of the herbicidal s-triazines has been studied extensively. Pseudomonas sp. strain ADP, which was isolated more than thirty years after the introduction of the s-triazine herbicides, has been the model system for most of these studies; however, several alternative catabolic pathways have also been identified. Over the last five years, considerable detail about the molecular mode of action of the s-triazine catabolic enzymes has been uncovered through acquisition of their atomic structures. These structural studies have also revealed insights into the evolutionary origins of this newly acquired metabolic capability. In addition, s-triazine-catabolizing bacteria and enzymes have been used in a range of applications, including bioremediation of herbicides and cyanuric acid, introducing metabolic resistance to plants, and as a novel selectable marker in fermentation organisms. In this review, we cover the discovery and characterization of bacterial strains, metabolic pathways and enzymes that catabolize the s-triazines. We also consider the evolution of these new enzymes and pathways and discuss the practical applications that have been considered for these bacteria and enzymes. One Sentence Summary: A detailed understanding of bacterial herbicide catabolic enzymes and pathways offer new evolutionary insights and novel applied tools.

A Review on Recent Treatment Technology for Herbicide Atrazine in Contaminated Environment

Atrazine is a kind of triazine herbicide that is widely used for weed control due to its good weeding effect and low price. The study of atrazine removal from the environment is of great significance due to the stable structure, difficult degradation, long residence time in environment, and toxicity on the organism and human beings. Therefore, a number of processing technologies are developed and widely employed for atrazine degradation, such as adsorption, photochemical catalysis, biodegradation, etc. In this article, with our previous research work, the progresses of researches about the treatment technology of atrazine are systematically reviewed, which includes the four main aspects of physicochemical, chemical, biological, and material-microbial-integrated aspects. The advantages and disadvantages of various methods are summarized and the degradation mechanisms are also evaluated. Specially, recent advanced technologies, both plant-microbial remediation and the material-microbial-integrated method, have been highlighted on atrazine degradation. Among them, the plant-microbial remediation is based on the combined system of soil-plant-microbes, and the material-microbial-integrated method is based on the synergistic effect of materials and microorganisms. Additionally, future research needs to focus on the excellent removal effect and low environmental impact of functional materials, and the coordination processing of two or more technologies for atrazine removal is also highlighted.

Genome Sequence of Arthrobacter sp. UKPF54-2, a Plant Growth-Promoting Rhizobacterial Strain Isolated from Paddy Soil

Arthrobacter sp. strain UKPF54-2, a plant growth-promoting rhizobacterium having the potential ability to control fungal and bacterial pathogens, was isolated from paddy soil in Kumamoto, Japan. We report here the whole-genome sequence of this strain.

Arthrobacter sp. strain UKPF54-2, a plant growth-promoting rhizobacterium having the potential ability to control fungal and bacterial pathogens, was isolated from paddy soil in Kumamoto, Japan. We report here the whole-genome sequence of this strain.

Self-immobilized biomixture with pellets of Aspergillus niger Y3 and Arthrobacter. sp ZXY-2 to remove atrazine in water: A bio-functions integration system

The microorganism Arthrobacter. ZXY-2 exhibits excellent degradation efficiency for atrazine in free cells. However, its poor fixability makes it hard to be kept and recycled in water. To conquer the problem, this work employed mycelial pellets of Aspergillus niger Y3 to immobilize ZXY-2, which formed a self-immobilized biomixture (SIB) to remove atrazine. SIB could completely degrade 57.3 mg/L atrazine within 10 h. The SIB exhibited the highest degradation efficiency at pH = 7 and 40 °C. Degradation of atrazine with initial concentrations of 57.3 mg/L and 17.5 mg/L was described well by zero and first-order reaction kinetics, respectively. The recycling experiments demonstrated that SIB could be recycled for 5 batches. The results of SEM, FT-IR, and zeta potential analysis showed that porous structure, functional groups, and electronegativity of SIB all contributed to its stable formation. Therefore, this study demonstrates that SIB could be formed stably and could remove atrazine efficiently.

Bioaugmentation of atrazine removal in constructed wetland: Performance, microbial dynamics, and environmental impacts

Constructed wetland (CW) is an efficient technology to treat urban storm water runoff. However, the CW has limited capacity to degrade atrazine, a frequently detected herbicide in runoff. Bioaugmentation provides a feasible enhanced alternative; nevertheless, incorporating bioaugmentation into CW is likely to perpetuate the environmental consequences and incur complex trade-offs between environmental improvement and burdens. Since few efforts were made to improve above situation, the present work proposed the application of bioaugmentation, and tested the feasibility from both efficiency and sustainability dimensions. Results showed that bioaugmentation markedly enhanced atrazine degradation from 5 mg/L to below the threshold value within 43 day by increasing functional atrazine-degrading bacteria. Pseudomonas and Arthrobacter significantly proliferated among atrazine-degrading bacterial genera, indicating high adaptability and atrazine-degrading contribution. With life cycle assessment, enhancing 1 kg of atrazine degradation could decrease environmental burdens with 27.60 kg 1,4-DCB-Eq of freshwater-ecotoxicity reduction, and achieve shorter payback period compared to non-bioaugmented CW.

Enhanced biodegradation of atrazine by Arthrobacter sp. DNS10 during co-culture with a phosphorus solubilizing bacteria: Enterobacter sp. P1

The interaction between pure culture microorganisms has been evaluated allowing for the enhanced biodegradation of various kinds of pollutants. Arthrobacter sp. DNS10 previously enriched in an atrazine-containing soil was capable of utilizing atrazine as the sole nitrogen source for growth, and Enterobacter sp. P1 is a phosphorus-solubilizing bacterium that releases various kinds of organic acids but lacks the ability to degrade atrazine. Whether strain P1 could enhance atrazine biodegradation by the degrader strain DNS10 was investigated in this experiment. Gas chromatography and high-performance liquid chromatography results showed that co-culture of both strains degraded 99.18 ± 1.00% of the atrazine (initial concentration was 100 mg L^-1), while the single strain DNS10 only degraded 38.57 ± 7.39% after a 48 h culture, and the resulting concentration of the atrazine final metabolite cyanuric acid were 63.91 ± 3.34 mg L^-1 and 26.60 ± 3.87 mg L^-1, respectively. In addition, the expression of the atrazine degradation-related genes trzN, atzB and atzC in co-culture treatments was 6.61, 1.81 and 3.09 times that of the single strain DNS10 culture treatment. A substrates utilization test showed that the atrazine-degrading metabolites ethylamine and isopropylamine could serve as the nitrogen source to support strain P1 growth, although strain P1 cannot degrade atrazine or utilize atrazine for growth. Furthermore, the pH of the medium was significantly decreased when strain P1 utilized ethylamine and isopropylamine as the nitrogen source for growth. The results suggest that nondegrader strain P1 could promote the atrazine biodegradation when co-cultured with strain DNS10. This phenomenon is due to metabolite exchange between the two strains. Culturing these two strains together is a new biostimulation strategy to enhance the biodegradation of atrazine by culturing these two strains together.

Biodegradation of persistent environmental pollutants by Arthrobacter sp

Persistent environmental pollutants are a growing problem around the world. The effective control of the pollutants is of great significance for human health. Some microbes, especially Arthrobacter, can degrade pollutants into nontoxic substances in various ways. Here, we review the biological properties of Arthrobacter adapting to a variety of environmental stresses, including starvation, hypertonic and hypotonic condition, oxidative stress, heavy metal stress, and low-temperature stress. Furthermore, we categorized the Arthrobacter species that can degrade triazines, organophosphorus, alkaloids, benzene, and its derivatives. Metabolic pathways behind the various biodegradation processes are further discussed. This review will be a helpful reference for comprehensive utilization of Arthrobacter species to tackle environmental pollutants.

Insight Into the Diversity and Possible Role of Plasmids in the Adaptation of Psychrotolerant and Metalotolerant Arthrobacter spp. to Extreme Antarctic Environments

Arthrobacter spp. are coryneform Gram-positive aerobic bacteria, belonging to the class Actinobacteria. Representatives of this genus have mainly been isolated from soil, mud, sludge or sewage, and are usually mesophiles. In recent years, the presence of Arthrobacter spp. was also confirmed in various extreme, including permanently cold, environments. In this study, 36 psychrotolerant and metalotolerant Arthrobacter strains isolated from petroleum-contaminated soil from the King George Island (Antarctica), were screened for the presence of plasmids. The identified replicons were thoroughly characterized in order to assess their diversity and role in the adaptation of Arthrobacter spp. to harsh Antarctic conditions. The screening process identified 11 different plasmids, ranging in size from 8.4 to 90.6 kb. A thorough genomic analysis of these replicons detected the presence of numerous genes encoding proteins that potentially perform roles in adaptive processes such as (i) protection against ultraviolet (UV) radiation, (ii) resistance to heavy metals, (iii) transport and metabolism of organic compounds, (iv) sulfur metabolism, and (v) protection against exogenous DNA. Moreover, 10 of the plasmids carry genetic modules enabling conjugal transfer, which may facilitate their spread among bacteria in Antarctic soil. In addition, transposable elements were identified within the analyzed plasmids. Some of these elements carry passenger genes, which suggests that these replicons may be actively changing, and novel genetic modules of adaptive value could be acquired by transposition events. A comparative genomic analysis of plasmids identified in this study and other available Arthrobacter plasmids was performed. This showed only limited similarities between plasmids of Antarctic Arthrobacter strains and replicons of other, mostly mesophilic, isolates. This indicates that the plasmids identified in this study are novel and unique replicons. In addition, a thorough meta-analysis of 247 plasmids of psychrotolerant bacteria was performed, revealing the important role of these replicons in the adaptation of their hosts to extreme environments.

Characterisation of an efficient atrazine-degrading bacterium, Arthrobacter sp. ZXY-2: an attempt to lay the foundation for potential bioaugmentation applications

BACKGROUND

The isolation of atrazine-degrading microorganisms with specific characteristics is fundamental for bioaugmenting the treatment of wastewater containing atrazine. However, studies describing the specific features of such microorganisms are limited, and further investigation is needed to improve our understanding of bioaugmentation.

RESULTS AND CONCLUSIONS

In this study, strain Arthrobacter sp. ZXY-2, which displayed a strong capacity to degrade atrazine, was isolated and shown to be a potential candidate for bioaugmentation. The factors associated with the biodegrading capacity of strain ZXY-2 were investigated, and how these factors likely govern the metabolic characteristics that control bioaugmentation functionality was determined. The growth pattern of Arthrobacter sp. ZXY-2 followed the Haldane-Andrews model with an inhibition constant (K_i) of 52.76 mg L^-1, indicating the possible augmentation of wastewater treatment with relatively high atrazine concentrations (> 50 ppm). Real-time quantitative PCR (RT-qPCR) results showed a positive correlation between the atrazine degradation rate and the expression levels of three functional genes (trzN, atzB, and atzC), which helped elucidate the role of strain ZXY-2 in bioaugmentation. In addition, multiple copies of the atzB gene were putatively identified, explaining the higher expression levels of this gene than those of the other functional genes. Multiple copies of the atzB gene may represent a compensatory mechanism that ensures the biodegradation of atrazine, a feature that should be exploited in future bioaugmentation applications.