Enhancing phytoremediation through the use of transgenics and endophytes. - Related Documents




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863801.0000Enhancing phytoremediation through the use of transgenics and endophytes. In the last decade, there has been an increase in research on improving the ability of plants to remove environmental pollution. Genes from microbes, plants, and animals are being used successfully to enhance the ability of plants to tolerate, remove, and degrade pollutants. Through expression of specific bacterial genes in transgenic plants, the phytotoxic effects of nitroaromatic pollutants were overcome, resulting in increased removal of these chemicals. Overexpression of mammalian genes encoding cytochrome P450s led to increased metabolism and removal of a variety of organic pollutants and herbicides. Genes involved in the uptake or detoxification of metal pollutants were used to enhance phytoremediation of this important class of pollutants. Transgenic plants containing specific bacterial genes converted mercury and selenium to less toxic forms. In addition to these transgenic approaches, the use of microbes that live within plants, termed endophytes, also led to improved tolerance to normally phytotoxic chemicals and increased removal of the pollutants. Bacteria that degraded a herbicide imparted resistance to the herbicide when inoculated into plants. In another study, plants harboring bacteria capable of degrading toluene were more tolerant to normally phytotoxic concentrations of the chemical, and transpired less of it into the atmosphere. This review examines the recent advances in enhancing phytoremediation through transgenic plant research and through the use of symbiotic endophytic microorganisms within plant tissues.200819086174
863710.9997Microbial reduction and resistance to selenium: Mechanisms, applications and prospects. Selenium is an essential trace element for humans, animals and microorganisms. Microbial transformations, in particular, selenium dissimilatory reduction and bioremediation applications have received increasing attention in recent years. This review focuses on multiple Se-reducing pathways under anaerobic and aerobic conditions, and the phylogenetic clustering of selenium reducing enzymes that are involved in these processes. It is emphasized that a selenium reductase may have more than one metabolic function, meanwhile, there are several Se(VI) and/or Se(IV) reduction pathways in a bacterial strain. It is noted that Se(IV)-reducing efficiency is inconsistent with Se(IV) resistance in bacteria. Moreover, we discussed the links of selenium transformations to biogeochemical cycling of other elements, roles of Se-reducing bacteria in soil, plant and digestion system, and the possibility of using functional genes involved in Se transformation as biomarker in different environments. In addition, we point out the gaps and perspectives both on Se transformation mechanisms and applications in terms of bioremediation, Se fortification or dietary supplementation.202234339989
973120.9997Towards an understanding of the genetics of bacterial metal resistance. Many bacteria show great promise for use in metal recovery. However, the genetics of metal-leaching, accumulation-resistance, and oxidation/reduction mechanisms of these bacteria is still an area of research in its infancy. The introduction of such genes into bacteria of economic importance would have application in biomining and environmental bioremediation.19911366923
861830.9997Insights into the microbial degradation and resistance mechanisms of glyphosate. Glyphosate, as one of the broad-spectrum herbicides for controlling annual and perennial weeds, is widely distributed in various environments and seriously threatens the safety of human beings and ecology. Glyphosate is currently degraded by abiotic and biotic methods, such as adsorption, photolysis, ozone oxidation, and microbial degradation. Of these, microbial degradation has become the most promising method to treat glyphosate because of its high efficiency and environmental protection. Microorganisms are capable of using glyphosate as a phosphorus, nitrogen, or carbon source and subsequently degrade glyphosate into harmless products by cleaving C-N and C-P bonds, in which enzymes and functional genes related to glyphosate degradation play an indispensable role. There have been many studies on the abiotic and biotic treatment technologies, microbial degradation pathways and intermediate products of glyphosate, but the related enzymes and functional genes involved in the glyphosate degradation pathways have not been further discussed. There is little information on the resistance mechanisms of bacteria and fungi to glyphosate, and previous investigations of resistance mechanisms have mainly focused on how bacteria resist glyphosate damage. Therefore, this review explores the microorganisms, enzymes and functional genes related to the microbial degradation of glyphosate and discusses the pathways of microbial degradation and the resistance mechanisms of microorganisms to glyphosate. This review is expected to provide reference for the application and improvement of the microbial degradation of glyphosate in microbial remediation.202236049517
863240.9996Microbial interactions in the arsenic cycle: adoptive strategies and applications in environmental management. Arsenic (As) is a nonessential element that is often present in plants and in other organisms. However, it is one of the most hazardous of toxic elements globally. In many parts of the world, arsenic contamination in groundwater is a serious and continuing threat to human health. Microbes play an important role in regulating the environmental fate of arsenic. Different microbial processes influence the biogeochemical cycling of arsenic in ways that affect the accumulation of different arsenic species in various ecosystem compartments. For example, in soil, there are bacteria that methylate arsenite to trimethylarsine gas, thereby releasing arsenic to the atmosphere.In marine ecosystems, microbes exist that can convert inorganic arsenicals to organic arsenicals (e.g., di- and tri-methylated arsenic derivatives, arsenocholine,arsenobetaine, arsenosugars, arsenolipids). The organo arsenicals are further metabolized to complete the arsenic cycle.Microbes have developed various strategies that enable them to tolerate arsenic and to survive in arsenic-rich environments. Such strategies include As exclusion from cells by establishing permeability barrier, intra- and extracellular sequestration,active efflux pumps, enzymatic reduction, and reduction in the sensitivity of cellular targets. These strategies are used either singly or in combination. In bacteria,the genes for arsenic resistance/detoxification are encoded by the arsenic resistance operons (ars operon).In this review, we have addressed and emphasized the impact of different microbial processes (e.g., arsenite oxidation, cytoplasmic arsenate reduction, respiratory arsenate reduction, arsenite methylation) on the arsenic cycle. Microbes are the only life forms reported to exist in heavy arsenic-contaminated environments. Therefore,an understanding of the strategies adopted by microbes to cope with arsenic stress is important in managing such arsenic-contaminated sites. Further future insights into the different microbial genes/proteins that are involved in arsenic resistance may also be useful for developing arsenic resistant crop plants.201323232917
863150.9996Bacterial metal(loid) resistance genes (MRGs) and their variation and application in environment: A review. Toxic metal(loid)s are widespread and permanent in the biosphere, and bacteria have evolved a wide variety of metal(loid) resistance genes (MRGs) to resist the stress of excess metal(loid)s. Via active efflux, permeability barriers, extracellular/intracellular sequestration, enzymatic detoxification and reduction in metal(loid)s sensitivity of cellular targets, the key components of bacterial cells are protected from toxic metal(loid)s to maintain their normal physiological functions. Exploiting bacterial metal(loid) resistance mechanisms, MRGs have been applied in many environmental fields. Based on the specific binding ability of MRGs-encoded regulators to metal(loid)s, MRGs-dependent biosensors for monitoring environmental metal(loid)s are developed. MRGs-related biotechnologies have been applied to environmental remediation of metal(loid)s by using the metal(loid) tolerance, biotransformation, and biopassivation abilities of MRGs-carrying microorganisms. In this work, we review the historical evolution, resistance mechanisms, environmental variation, and environmental applications of bacterial MRGs. The potential hazards, unresolved problems, and future research directions are also discussed.202336758696
863560.9996Techniques for enhancing the tolerance of industrial microbes to abiotic stresses: A review. The diversity of stress responses and survival strategies evolved by microorganism enables them to survive and reproduce in a multitude of harsh environments, whereas the discovery of the underlying resistance genes or mechanisms laid the foundation for the directional enhancement of microbial tolerance to abiotic stresses encountered in industrial applications. Many biological techniques have been developed for improving the stress resistance of industrial microorganisms, which greatly benefited the bacteria on which industrial production is based. This review introduces the main techniques for enhancing the resistance of microorganisms to abiotic stresses, including evolutionary engineering, metabolic engineering, and process engineering, developed in recent years. In addition, we also discuss problems that are still present in this area and offer directions for future research.202031206805
973270.9996Interactions of heavy metals with bacteria. The toxicity of heavy metals to bacteria, with particular reference to metal forms and species, has been reviewed. Factors which influence metal forms and thus their potential toxicity, such as pH, chelation and competitive interactions have been discussed. The mechanisms whereby bacteria may influence the forms of heavy metals to which they are exposed have been discussed with reference to the importance of the role of bacteria in immobilisation and environmental cycling of metals. Bacterial resistance to metal toxicity is an environmentally important phenomenon. It may occur from non-specific mechanisms, such as impermeability of the cell, or it may be due to specific resistance transfer factors. The coincidence and co-selection of resistance factors for antibiotics and heavy metals in bacterial populations and the clinical implications of this have been described.19806988964
824980.9996Biocontrol Traits Correlate With Resistance to Predation by Protists in Soil Pseudomonads. Root-colonizing bacteria can support plant growth and help fend off pathogens. It is clear that such bacteria benefit from plant-derived carbon, but it remains ambiguous why they invest in plant-beneficial traits. We suggest that selection via protist predation contributes to recruitment of plant-beneficial traits in rhizosphere bacteria. To this end, we examined the extent to which bacterial traits associated with pathogen inhibition coincide with resistance to protist predation. We investigated the resistance to predation of a collection of Pseudomonas spp. against a range of representative soil protists covering three eukaryotic supergroups. We then examined whether patterns of resistance to predation could be explained by functional traits related to plant growth promotion, disease suppression and root colonization success. We observed a strong correlation between resistance to predation and phytopathogen inhibition. In addition, our analysis highlighted an important contribution of lytic enzymes and motility traits to resist predation by protists. We conclude that the widespread occurrence of plant-protective traits in the rhizosphere microbiome may be driven by the evolutionary pressure for resistance against predation by protists. Protists may therefore act as microbiome regulators promoting native bacteria involved in plant protection against diseases.202033384680
869190.9996Genetic basis and importance of metal resistant genes in bacteria for bioremediation of contaminated environments with toxic metal pollutants. Metal pollution is one of the most persistent and complex environmental issues, causing threat to the ecosystem and human health. On exposure to several toxic metals such as arsenic, cadmium, chromium, copper, lead, and mercury, several bacteria has evolved with many metal-resistant genes as a means of their adaptation. These genes can be further exploited for bioremediation of the metal-contaminated environments. Many operon-clustered metal-resistant genes such as cadB, chrA, copAB, pbrA, merA, and NiCoT have been reported in bacterial systems for cadmium, chromium, copper, lead, mercury, and nickel resistance and detoxification, respectively. The field of environmental bioremediation has been ameliorated by exploiting diverse bacterial detoxification genes. Genetic engineering integrated with bioremediation assists in manipulation of bacterial genome which can enhance toxic metal detoxification that is not usually performed by normal bacteria. These techniques include genetic engineering with single genes or operons, pathway construction, and alternations of the sequences of existing genes. However, numerous facets of bacterial novel metal-resistant genes are yet to be explored for application in microbial bioremediation practices. This review describes the role of bacteria and their adaptive mechanisms for toxic metal detoxification and restoration of contaminated sites.201626860944
8626100.9996Challenges Associated With the Use of Metal and Metal Oxide Nanoparticles as Antimicrobial Agents: A Review of Resistance Mechanisms and Environmental Implications. The use of metal and metal oxide nanoparticles has been suggested as a means of combating antibiotic-resistant bacteria (ARB). This is due to the ability of nanoparticles to target numerous sites inside the bacterial cell. Microbes can, however, develop a resistance to hazardous environments. Soil microorganisms have evolved resistance to specific metals in soil by employing alternative survival strategies, like those adopted against antibiotics. Because of this survival mechanism, bacteria have been able to develop defense mechanisms to deal with metallic nanoparticles. Resistance has evolved in human pathogens to therapies that use metallic nanoparticles, such as silver nanoparticles. Metallic nanoparticles and antibiotics have currently been proven to be ineffective against several infections. Due to these concerns, scientists are investigating whether nanoparticles might cause environmental harm and potentially breed microbes that are resistant to both inorganic and organic nanoparticles. The increased use of inorganic nanoparticles has thus been shown to result in contaminations in wastewater, facilitating horizontal gene transfer among bacterial populations. The resistance mechanism of metallic nanoparticles, role in antibiotic resistance, and a potential solution to the environment's toxicity from nanoparticles are all discussed in this review.202540711446
9730110.9996At the Nexus of Antibiotics and Metals: The Impact of Cu and Zn on Antibiotic Activity and Resistance. Environmental influences on antibiotic activity and resistance can wreak havoc with in vivo antibiotic efficacy and, ultimately, antimicrobial chemotherapy. In nature, bacteria encounter a variety of metal ions, particularly copper (Cu) and zinc (Zn), as contaminants in soil and water, as feed additives in agriculture, as clinically-used antimicrobials, and as components of human antibacterial responses. Importantly, there is a growing body of evidence for Cu/Zn driving antibiotic resistance development in metal-exposed bacteria, owing to metal selection of genetic elements harbouring both metal and antibiotic resistance genes, and metal recruitment of antibiotic resistance mechanisms. Many classes of antibiotics also form complexes with metal cations, including Cu and Zn, and this can hinder (or enhance) antibiotic activity. This review highlights the ways in which Cu/Zn influence antibiotic resistance development and antibiotic activity, and in so doing impact in vivo antibiotic efficacy.201728526548
9323120.9996Metal resistance and accumulation in bacteria. Recent research on the ecology, physiology and genetics of metal resistance and accumulation in bacteria has significantly increased the basic understanding of microbiology in these areas. Research has clearly demonstrated the versatility of bacteria to cope with toxic metal ions. For example, certain strains of bacteria can efficiently efflux toxic ions such as cadmium, that normally exert an inhibitory effect on bacteria. Some bacteria such as Escherichia coli and Staphylococcus sp. can volatilize mercury via enzymatic transformations. It is also noteworthy that many of these resistance mechanisms are encoded on plasmids or transposons. By expanding the knowledge on metal-resistance and accumulation mechanisms in bacteria, it may be possible to utilize certain strains to recover precious metals such as gold and silver, or alternatively remove toxic metal ions from environments or products where their presence is undesirable.198714543146
8634130.9996Synthetic bacteria designed using ars operons: a promising solution for arsenic biosensing and bioremediation. The global concern over arsenic contamination in water due to its natural occurrence and human activities has led to the development of innovative solutions for its detection and remediation. Microbial metabolism and mobilization play crucial roles in the global cycle of arsenic. Many microbial arsenic-resistance systems, especially the ars operons, prevalent in bacterial plasmids and genomes, play vital roles in arsenic resistance and are utilized as templates for designing synthetic bacteria. This review novelty focuses on the use of these tailored bacteria, engineered with ars operons, for arsenic biosensing and bioremediation. We discuss the advantages and disadvantages of using synthetic bacteria in arsenic pollution treatment. We highlight the importance of genetic circuit design, reporter development, and chassis cell optimization to improve biosensors' performance. Bacterial arsenic resistances involving several processes, such as uptake, transformation, and methylation, engineered in customized bacteria have been summarized for arsenic bioaccumulation, detoxification, and biosorption. In this review, we present recent insights on the use of synthetic bacteria designed with ars operons for developing tailored bacteria for controlling arsenic pollution, offering a promising avenue for future research and application in environmental protection.202438709285
8690140.9996Cellular and genetic mechanism of bacterial mercury resistance and their role in biogeochemistry and bioremediation. Mercury (Hg) is a highly toxic element that occurs at low concentrations in nature. However, various anthropogenic and natural sources contribute around 5000 to 8000 metric tons of Hg per year, rapidly deteriorating the environmental conditions. Mercury-resistant bacteria that possess the mer operon system have the potential for Hg bioremediation through volatilization from the contaminated milieus. Thus, bacterial mer operon plays a crucial role in Hg biogeochemistry and bioremediation by converting both reactive inorganic and organic forms of Hg to relatively inert, volatile, and monoatomic forms. Both the broad-spectrum and narrow-spectrum bacteria harbor many genes of mer operon with their unique definitive functions. The presence of mer genes or proteins can regulate the fate of Hg in the biogeochemical cycle in the environment. The efficiency of Hg transformation depends upon the nature and diversity of mer genes present in mercury-resistant bacteria. Additionally, the bacterial cellular mechanism of Hg resistance involves reduced Hg uptake, extracellular sequestration, and bioaccumulation. The presence of unique physiological properties in a specific group of mercury-resistant bacteria enhances their bioremediation capabilities. Many advanced biotechnological tools also can improve the bioremediation efficiency of mercury-resistant bacteria to achieve Hg bioremediation.202234464861
8617150.9995Antibiotic removal by microalgae-bacteria consortium: Metabolic pathways and microbial responses. The proliferation of antibiotic-resistance genes is a result of the rise in the discharge of residual antibiotics into waterbodies from a variety of sources. Antibiotic removal by microalgae-bacteria consortium has been shown to be effective, therefore, there is a need to understand the involved microbial processes. This review summarizes the microbiological removal mechanisms of antibiotics by the microalgae-bacteria consortium, such as biosorption, bioaccumulation, and biodegradation. Factors that influence antibiotic removal are discussed. Co-metabolism of nutrients and antibiotics in the microalgae-bacteria consortium and the metabolic pathways revealed by omics technologies are also highlighted. Furthermore, the responses of microalgae and bacteria to antibiotic stress are elaborated, including reactive oxidizing species (ROS) generation and its effects on photosynthesis machinery, antibiotic stress tolerance, microbial community shift, and the emergence of antibiotic resistance genes (ARGs). Finally, we offer a prospective solutions for the optimization and applications of microalgae-bacteria symbiotic systems for antibiotic removal.202337279806
9636160.9995A comprehensive review on biodegradation of tetracyclines: Current research progress and prospect. The release of tetracyclines (TCs) in the environment is of significant concern because the residual antibiotics may promote resistance in pathogenic microorganisms, and the transfer of antibiotic resistance genes poses a potential threat to ecosystems. Microbial biodegradation plays an important role in removing TCs in both natural and artificial systems. After long-term acclimation, microorganisms that can tolerate and degrade TCs are retained to achieve efficient removal of TCs under the optimum conditions (e.g. optimal operational parameters and moderate concentrations of TCs). To date, cultivation-based techniques have been used to isolate bacteria or fungi with potential degradation ability. Moreover, the biodegradation mechanism of TCs can be unveiled with the development of chemical analysis (e.g. UPLC-Q-TOF mass spectrometer) and molecular biology techniques (e.g. 16S rRNA gene sequencing, multi-omics sequencing, and whole genome sequencing). In this review, we made an overview of the biodegradation of TCs in different systems, refined functional microbial communities and pure isolates relevant to TCs biodegradation, and summarized the biodegradation products, pathways, and degradation genes of TCs. In addition, ecological risks of TCs biodegradation were considered from the perspectives of metabolic products toxicity and resistance genes. Overall, this article aimed to outline the research progress of TCs biodegradation and propose future research prospects.202234995606
9727170.9995Metal Toxicity and Resistance in Plants and Microorganisms in Terrestrial Ecosystems. Metals are major abiotic stressors of many organisms, but their toxicity in plants is not as studied as in microorganisms and animals. Likewise, research in plant responses to metal contamination is sketchy. Candidate genes associated with metal resistance in plants have been recently discovered and characterized. Some mechanisms of plant adaptation to metal stressors have been now decrypted. New knowledge on microbial reaction to metal contamination and the relationship between bacterial, archaeal, and fungal resistance to metals has broadened our understanding of metal homeostasis in living organisms. Recent reviews on metal toxicity and resistance mechanisms focused only on the role of transcriptomics, proteomics, metabolomics, and ionomics. This review is a critical analysis of key findings on physiological and genetic processes in plants and microorganisms in responses to soil metal contaminations.202030725190
8344180.9995Role of environmental stresses in elevating resistance mutations in bacteria: Phenomena and mechanisms. Mutations are an important origin of antibiotic resistance in bacteria. While there is increasing evidence showing promoted resistance mutations by environmental stresses, no retrospective research has yet been conducted on this phenomenon and its mechanisms. Herein, we summarized the phenomena of stress-elevated resistance mutations in bacteria, generalized the regulatory mechanisms and discussed the environmental and human health implications. It is shown that both chemical pollutants, such as antibiotics and other pharmaceuticals, biocides, metals, nanoparticles and disinfection byproducts, and non-chemical stressors, such as ultraviolet radiation, electrical stimulation and starvation, are capable of elevating resistance mutations in bacteria. Notably, resistance mutations are more likely to occur under sublethal or subinhibitory levels of these stresses, suggesting a considerable environmental concern. Further, mechanisms for stress-induced mutations are summarized in several points, namely oxidative stress, SOS response, DNA replication and repair systems, RpoS regulon and biofilm formation, all of which are readily provoked by common environmental stresses. Given bacteria in the environment are confronted with a variety of unfavorable conditions, we propose that the stress-elevated resistance mutations are a universal phenomenon in the environment and represent a nonnegligible risk factor for ecosystems and human health. The present review identifies a need for taking into account the pollutants' ability to elevate resistance mutations when assessing their environmental and human health risks and highlights the necessity of including resistance mutations as a target to prevent antibiotic resistance evolution.202235691443
9728190.9995Metagenomic analysis of metal(loid)s resistance genes and its environmental applications. Heavy metals are widely used to satiate the demands of growing industrialization and modern life. However, the presence of metal in large quantities in the ecosystem significantly impacts all life forms, particularly microorganisms. Many bacterial strains have developed metal resistance genes (MRG) to survive in extreme conditions through various mechanisms, such as active efflux, sequestration, permeability barriers, or co-resistance with antibiotic resistance genes. Metagenomic analysis is a powerful approach that enables the exploration of the functional repertoire and diversity of microorganisms, providing deeper insights into the mechanisms underlying the development of MRGs, and the active metabolites they produce to adapt to the polluted environments. With the advancement of these techniques, the knowledge can be further applied to environmental applications, such as bioremediation, biomonitoring, and synthetic biology. Bacteria with metal toxicity tolerance can be employed to enhance environmental sustainability and mitigate potential hazards.202540992856