Toxicity of ionic liquids to Clostridium sp. and effects on uranium biosorption

Effects of ionic liquids on biomembranes: A review on recent biophysical studies

Ionic liquids (ILs) have been emerged as a versatile class of compounds that can be easily tuned to achieve desirable properties for various applications. The ability of ILs to interact with biomembranes has attracted significant interest, as they have been shown to modulate membrane properties in ways that may have implications for various biological processes. This review provides an overview of recent studies that have investigated the interaction between ILs and biomembranes. We discuss the effects of ILs on the physical and chemical properties of biomembranes, including changes in membrane fluidity, permeability, and stability. We also explore the mechanisms underlying the interaction of ILs with biomembranes, such as electrostatic interactions, hydrogen bonding, and van der Waals forces. Additionally, we discuss the future prospects of this field.

Response and Dynamic Change of Microbial Community during Bioremediation of Uranium Tailings by Bacillus sp

Bacillus sp. is widely used in the remediation of uranium-contaminated sites. However, little is known about the competitive process of microbial community in the environment during bioremediation. The bioremediation of uranium tailings using Bacillus sp. was explored, and the bacterial community was analyzed by high-throughput sequencing at different stages of remediation. Bacillus sp. reduced the leaching of uranium from uranium tailings. The lowest uranium concentration was 17.25 μg/L. Alpha diversity revealed that the abundance and diversity of microorganisms increased with the extension of the culture time. The microbial abundance and diversity were higher in the treatment group than in the control group. The dominant species at the phyla level were Firmicutes and Proteobacteria in the uranium tailings environment, whereas the phylum of Proteobacteria was significantly increased in the treatment group. Based on the genus level, the proportions of Arthrobacter, Rhodococcus and Paenarthrobacter decreased significantly, whereas those of Clostridium sp., Bacillus and Pseudomonas increased dramatically. Hence, the remediation of uranium contamination in the environment was due to the functional microorganisms, which gradually became the dominant strain in the treatment, such as Desulfotomaculum, Desulfosporporosinus, Anaerocolumna, Ruminiclostridium and Burkholderia. These findings provided a promising outlook of the potential for remediation strategies of soil contaminated by uranium. The dynamic characteristics of the microbial community are likely to provide a foundation for the bioremediation process in practice.

Cumulative impact assessment of hazardous ionic liquids towards aquatic species using risk assessment methods

In the present research work, a comprehensive tool for cumulative ecotoxicological impact assessment of ionic liquids (ILs) to aquatic life has been constructed. Using the probabilistic tool, impact of individual ILs to a group of aquatic species is assessed by chemical toxicity distributions (CTDs). The impact of group of ILs to individual aquatic species is assessed by species sensitivity distributions (SSDs). Acute toxicity data of imidazolium ILs with chloride (Cl^-), bromide (Br^-), tetrafluoroborate (BF4^-), and hexafluorophosphate (PF6^-) anions are used in CTD and SSD. Allowable concentrations for a group of Imidazolium ILs with the same mode of action (SMOA) to five aquatic species; Daphnia magna, Vibrio fischeri, Algae, Zebrafish, and Escherichia coli are estimated by CTDs. It has been concluded that 1-Butyl-3-methylimidazolium chloride (BMIMCl) possess the lowest risk at an acceptable risk value of 750 × 10^-5 mmol/L which is 12% less than that of OMIMCl. Furthermore, the sensitivities towards the aquatic species reveal that from the studied ILs, BMIMBF4 with an acceptable risk value of 3200 × 10^-5 mmol/L is the most suitable IL towards the selected aquatic species. Hence, current work provides cumulative allowable concentrations and acceptable risk values for ILs which release to aquatic compartment of ecosystem.

Microbial interaction with and tolerance of radionuclides: underlying mechanisms and biotechnological applications

Radionuclides (RNs) generated by nuclear and civil industries are released in natural ecosystems and may have a hazardous impact on human health and the environment. RN-polluted environments harbour different microbial species that become highly tolerant of these elements through mechanisms including biosorption, biotransformation, biomineralization and intracellular accumulation. Such microbial-RN interaction processes hold biotechnological potential for the design of bioremediation strategies to deal with several contamination problems. This paper, with its multidisciplinary approach, provides a state-of-the-art review of most research endeavours aimed to elucidate how microbes deal with radionuclides and how they tolerate ionizing radiations. In addition, the most recent findings related to new biotechnological applications of microbes in the bioremediation of radionuclides and in the long-term disposal of nuclear wastes are described and discussed.

Mechanisms of action of ionic liquids on living cells: the state of the art

Ionic liquids (ILs) are a relatively new class of organic electrolytes composed of an organic cation and either an organic or inorganic anion, whose melting temperature falls around room-temperature. In the last 20 years, the toxicity of ILs towards cells and micro-organisms has been heavily investigated with the main aim to assess the risks associated with their potential use in (industrial) applications, and to develop strategies to design greener ILs. Toxicity, however, is synonym with affinity, and this has stimulated, in turn, a series of biophysical and chemical-physical investigations as well as few biochemical studies focused on the mechanisms of action (MoAs) of ILs, key step in the development of applications in bio-nanomedicine and bio-nanotechnology. This review has the intent to present an overview of the state of the art of the MoAs of ILs, which have been the focus of a limited number of studies but still sufficient enough to provide a first glimpse on the subject. The overall picture that emerges is quite intriguing and shows that ILs interact with cells in a variety of different mechanisms, including alteration of lipid distribution and cell membrane viscoelasticity, disruption of cell and nuclear membranes, mitochondrial permeabilization and dysfunction, generation of reactive oxygen species, chloroplast damage (in plants), alteration of transmembrane and cytoplasmatic proteins/enzyme functions, alteration of signaling pathways, and DNA fragmentation. Together with our earlier review work on the biophysics and chemical-physics of IL-cell membrane interactions (Biophys. Rev. 9:309, 2017), we hope that the present review, focused instead on the biochemical aspects, will stimulate a series of new investigations and discoveries in the still new and interdisciplinary field of "ILs, biomolecules, and cells."

Ionic Liquids for Therapeutic and Drug Delivery Applications

BACKGROUND

Ionic liquids (ILs) are ionic compounds with highly tunable and remarkable properties which make them an important candidate in multiple domains such as extraction, synthesis, analytics, catalysis, biotechnology, therapeutics as well as pharmaceutical sciences.

OBJECTIVE

This review systematically highlights the classification, properties and toxicity of ionic liquids. It focuses on exploring the biological activity of ionic liquids, which includes antimicrobial and anticancer property along with an emphasis on the concept of Active Pharmaceutical Ingredient- Ionic Liquids (API-ILs) for explaining the emulsifier and solubility enhancement property of ILs. An elaborative discussion on the application of ILs for the development of oral, transdermal and topical drug delivery systems has also been presented with suitable literature support.

CONCLUSION

Ionic liquids possess exceptional potential in the field of medicine, biology and chemistry.

Anaerobic reduction of europium by a Clostridium strain as a strategy for rare earth biorecovery

The biorecovery of europium (Eu) from primary (mineral deposits) and secondary (mining wastes) resources is of interest due to its remarkable luminescence properties, important for modern technological applications. In this study, we explored the tolerance levels, reduction and intracellular bioaccumulation of Eu by a site-specific bacterium, Clostridium sp. 2611 isolated from Phalaborwa carbonatite complex. Clostridium sp. 2611 was able to grow in minimal medium containing 0.5 mM Eu³⁺. SEM-EDX analysis confirmed an association between Eu precipitates and the bacterium, while TEM-EDX analysis indicated intracellular accumulation of Eu. According to the HR-XPS analysis, the bacterium was able to reduce Eu³⁺ to Eu²⁺ under growth and non-growth conditions. Preliminary protein characterization seems to indicate that a cytoplasmic pyruvate oxidoreductase is responsible for Eu bioreduction. These findings suggest the bioreduction of Eu³⁺ by Clostridium sp. as a resistance mechanism, can be exploited for the biorecovery of this metal.

Responses exhibited by various microbial groups relevant to uranium exposure

There is a strong interest in knowing how various microbial systems respond to the presence of uranium (U), largely in the context of bioremediation. There is no known biological role for uranium so far. Uranium is naturally present in rocks and minerals. The insoluble nature of the U(IV) minerals keeps uranium firmly bound in the earth's crust minimizing its bioavailability. However, anthropogenic nuclear reaction processes over the last few decades have resulted in introduction of uranium into the environment in soluble and toxic forms. Microbes adsorb, accumulate, reduce, oxidize, possibly respire, mineralize and precipitate uranium. This review focuses on the microbial responses to uranium exposure which allows the alteration of the forms and concentrations of uranium within the cell and in the local environment. Detailed information on the three major bioprocesses namely, biosorption, bioprecipitation and bioreduction exhibited by the microbes belonging to various groups and subgroups of bacteria, fungi and algae is provided in this review elucidating their intrinsic and engineered abilities for uranium removal. The survey also highlights the instances of the field trials undertaken for in situ uranium bioremediation. Advances in genomics and proteomics approaches providing the information on the regulatory and physiologically important determinants in the microbes in response to uranium challenge have been catalogued here. Recent developments in metagenomics and metaproteomics indicating the ecologically relevant traits required for the adaptation and survival of environmental microbes residing in uranium contaminated sites are also included. A comprehensive understanding of the microbial responses to uranium can facilitate the development of in situ U bioremediation strategies.

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine

Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in the form of ionic liquid species. The main aim of this Review is to attract a broad audience of chemical, biological, and medical scientists to study advantages of ionic liquid pharmaceutics. Overall, the discussed data highlight the importance of the research direction defined as "Ioliomics", studies of ions in liquids in modern chemistry, biology, and medicine.

Effects of two kinds of imidazolium-based ionic liquids on the characteristics of steroid-transformation Arthrobacter simplex

Background

Ionic liquids (ILs) are a promising alternative for organic solvents because these liquids exhibit unique properties and enhanced steroid 1-dehydrogenation biotransformation caused by Arthrobacter simplex CPCC 140451 (ASP). However, the effect of ILs on the whole cell itself remains poorly understood and must be further investigated.

Results

A comparative investigation was performed to determine the effect of imidazolium-based ILs, namely, hydrophobic [PrMIm]PF₆, and hydrophilic [PrMIm]BF₄, on the steroid conversion, activity, permeability, and material basis of ASP cells. Both ILs weakened permeability barriers, enhanced steroid transformation, whereas reduced the activity of cells. The influence of [PrMIm]PF₆ on the steroid conversion, permeability and activity of cells is more serious than that of [PrMIm]BF₄ Transmission electron microscopy micrographs directly showed wrinkles, gross creases, and several small pores in ILs-treated cells surface. The total lipid content of [PrMIm]BF₄-treated cells reduced by 8.3 %, while that of [PrMIm]PF₆-treated cells reduced twice more, among which the content of long-chain fatty acids was decreased, whereas the content of unsaturated fatty acids was increased. The protein profile of LC–MS/MS revealed that the reduced proteins of cells treated with the two ILs were mainly located in the cytoplasm and plasma membrane, 19.27 % of reduced proteins were located on the cell membrane for [PrMIm]PF₆-pretreated cells, whereas only 12.8 % for [PrMIm]BF₄-pretreated cells. It suggests that most reduced proteins functioned in energy production and conversion, material transport and metabolism, signal recognition and transmission, transcription, and translation and posttranslational modification. In particular, the identified differential proteins functioned in the pentose phosphate pathway, synthesis of purines and pyrimidines, and oxidative phosphorylation and fatty acid pathway.

Conclusion

Treatment with ILs improved permeability at the molecular level and exerted significant positive effects on steroid conversion. This study provides a material basis and elucidates the mechanisms underlying cellular changes that enhanced conversion rate.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0518-3) contains supplementary material, which is available to authorized users.

Antimicrobial activity and cytotoxicity of piperazinium- and guanidinium-based ionic liquids

Twelve piperazinium- and guanidinium-based ionic liquids (ILs) were synthesized, and characterized by (1)H nuclear magnetic resonance (NMR), thermal gravimetric analyzer (TGA) and differential scanning calorimetry (DSC). The antimicrobial activity and cytotoxicity have been investigated to provide the information whether the newly synthesized ILs are toxic or not. The antimicrobial effects of these ILs on gram negative and gram positive bacteria are evaluated on the basis of the minimum inhibitory concentration (MIC) measurements. The membrane damages of bacteria in the presence of ILs are observed by scanning electron microscopy (SEM). The cytotoxicity data of the ILs on HEK-293 and C6 cells are obtained by MTT cell viability assay. The disruption of cell cycle is analyzed by the flow cytometry. The results show that most of the ILs exhibit low toxicity, and the ILs with tetrafluoroborate anion and with benzene ring on cation are the species with relatively high toxicity among the studied ILs. The fundamental data and results can provide some useful information for the further studies and applications of the ILs.

Bioreduction of U(VI) and stability of immobilized uranium under suboxic conditions

In order to study the bioreduction of U(VI) and stability of immobilized uranium under suboxic conditions, microcosm were amended with ethanol, lactate and glucose, and incubated under suboxic conditions. During the incubation, total dissolved U in amended microcosms decreased from 0.95 mg/L to 0.03 mg/L. Pyrosequencing results showed that, the proportion of anaerobic microorganisms capable of reducing U(VI) under suboxic conditions was small compared with that under anoxic conditions; the proportion of aerobic and facultative anaerobic microorganisms capable of consuming the dissolved oxygen was large; and some of the facultative anaerobic microorganisms could reduce U(VI). These results indicated that different microbial communities were responsible for the bioreduction of U(VI) under suboxic and anoxic conditions. After the electron donors were exhausted, total dissolved U in the amended microcosms remained unchanged, while the U(VI)/U(IV) ratio in the solid phase of sediments increased obviously. This implied that the performance of bioreduction of the U(VI) can be maintained under suboxic condition.

Assessing toxic effects of [Omim]Cl and [Omim]BF4 in zebrafish adults using a biomarker approach

In the present study, the toxic effects of 1-octyl-3-methylimidazolium chloride ([Omim]Cl) and 1-octyl-3-methylimidazolium tetrafluoroborate ([Omim]BF4) on the zebrafish livers were studied at 0, 5, 10, 20, and 40 mg L(-1) on the 7th and 14th days. In addition, the concentrations of [Omim]Cl and [Omim]BF4 in the test water, the acute toxicity of the two ionic liquids (ILs), and the influence of anions on the toxicity of the ILs were evaluated. The acute toxicity test results showed 50 % lethal concentration (LC50) values of 152.3 ± 12.1 mg L(-1) for [Omim]Cl and 144.0 ± 11.4 mg L(-1) for [Omim]BF4. At the lowest concentration investigated (5 mg L(-1)), [Omim]Cl and [Omim]BF4 did not significantly affect zebrafish during the exposure period. However, the toxic effects of these substances were enhanced as dosing concentrations and exposure times were increased. Levels of reactive oxygen species (ROS) were significantly enhanced on the 7th day after 20 mg L(-1) and on the 14th day after 10 mg L(-1) of either substance was applied, resulting in oxidative damage, such as lipid peroxidation and DNA damage. The experimental results also indicated little effect of the anions on the toxicity of ILs and consistent toxic effects of [Omim]Cl and [Omim]BF4. Graphical Abstract The graphical abstract for the present study after exposure to [Omim]Cl and [Omim]BF4. The letter R represents the anions Cl(-) and BF4 (.)

Quaternary ammonium salts with tetrafluoroborate anion: Phytotoxicity and oxidative stress in terrestrial plants

This paper discusses the impact of four quaternary ammonium salts (QAS) such as tetraethylammonium tetrafluoroborate [TEA][BF4], tetrabutylammonium tetrafluoroborate [TBA][BF4], tetrahexylammonium tetrafluoroborate [THA][BF4], and tetraoctylammonium tetrafluoroborate [TOA][BF4] on the growth and development of spring barley and common radish. Analogous tests were performed with the inorganic salt ammonium tetrafluoroborate [A][BF4] for comparison purposes. Results indicated that the phytotoxicity of the QAS applied is dependent on the concentration of the substance and their number of carbon atoms. The most toxic compound was [TBA][BF4], causing the greatest drop in fresh weight of both study plants, similar to the phytotoxic effects of [A][BF4]. All the tested compounds caused oxidative stress in spring barley and common radish seedlings due to a drop in the chlorophyll content. Stress was also observed in plants, which was indicated by the increased level of ROS (reactive oxygen species) such as H2O2 and lipid peroxidation of MDA (malondialdehyde). Due to the stress, both plants displayed changes in the activity of antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Based on the results of the study, it was concluded that changes in chlorophyll levels and peroxidase activity are the best biomarkers to determine oxidative stress in plants.

Toxicity of synthetic herbicides containing 2,4-D and MCPA moieties towards Pseudomonas putida mt-2 and its response at the level of membrane fatty acid composition

One of the attempts to create more effective herbicidal compounds includes the use of ionic liquids. Herbicidal ionic liquids have more effective biological activity, they are less volatile, more thermally stable, and exhibit superior efficiency in comparison to typically employed herbicides, allowing the reduction of the herbicide dose applied per hectare. However, studies on the environmental toxicity of this group of compounds are very rarely available. Environmental toxicity is an important factor, showing the concentration of compounds that has negative effects on soil bacteria including those responsible for biodegradation processes. Therefore, potential toxicity of four herbicidal ionic liquids (HILs) precursors containing 2,4-D and MCPA moieties was tested with the well investigated model organism for toxicity and adaptation, Pseudomonas putida mt-2. Results were compared to those obtained for commercial 2,4-D and MCPA herbicides. Next to growth inhibition, given as EC50, changes in the isomerisation of cis to trans unsaturated fatty acids were applied as proxy for cellular stress adaptation to toxic substances. The results revealed that all investigated precursors of HILs showed lower toxicity compared to commercialized synthetic herbicides 2,4-D and MCPA. The collected data on toxicity of HILs together with their physico-chemical properties might be useful for assessing the potential risk of the environmental pollution as well as guidelines for setting the legislation for their future use.

Metagenomic analysis of microbial community in uranium-contaminated soil

Uranium tailing is a serious pollution challenge for the environment. Based on metagenomic sequencing analysis, we explored the functional and structural diversity of the microbial community in six soil samples taken at different soil depths from uranium-contaminated and uncontaminated areas. Kyoto Encyclopedia of Genes and Genomes Orthology (KO) groups were obtained using a Basic Local Alignment Search Tool search based on the universal protein resource database. The KO-pathway network was then constructed using the selected KOs. Finally, alpha and beta diversity analyses were performed to explore the differences in soil bacterial diversity between the radioactive soil and uncontaminated soil. In total, 30-68 million high-quality reads were obtained. Sequence assembly yielded 286,615 contigs; and these contigs mostly annotated to 1699 KOs. The KO distributions were similar among the six soil samples. Moreover, the proportion of the metabolism of other amino acids (e.g., beta-alanine, taurine, and hypotaurine) and signal transduction was significantly lower in radioactive soil than in uncontaminated soil, whereas the proportion of membrane transport and carbohydrate metabolism was higher. Additionally, KOs were mostly enriched in ATP-binding cassette transporters and two-component systems. According to diversity analyses, Actinobacteria and Proteobacteria were the dominant phyla in radioactive and uncontaminated soil, and Robiginitalea, Microlunatus, and Alicyclobacillus were the dominant genera in radioactive soil. Taken together, these results demonstrate that soil microbial community, structure, and functions show significant changes in uranium-contaminated soil. The dominant categories such as Actinobacteria and Proteobacteria may be applied in environmental governance for uranium-contaminated soil in southern China.

The phytotoxicity of ionic liquids from natural pool of (-)-menthol with tetrafluoroborate anion

Over the last several decades, ionic liquids have become a promising alternative to conventional organic solvents. Initially, ionic liquids were described as "environmentally friendly" substances. However, the results of numerous studies proved that the effects of these compounds on individual ecosystems might be adverse. The presented paper discusses the effect of ionic salts containing natural chiral substituent: (1R,2S,5R)-(-)-menthol in cation and a tetrafluoroborate anion of a general formula of [Cn-Im-Men][BF4] of implementation into the soil on the growth of spring barley and common radish in their early development stages. The obtained results showed that the greatest phytotoxicity was exhibited by ionic liquids containing substituents with the smallest possible number of carbon atoms. The further increase in the length of the chain did not increase the toxicity of these salts for terrestrial plants. Moreover, a compound with a substituent having a chain length of 11 carbon atoms was found to be non-toxic to common radish. The experiment under discussion showed also the effect of these tetrafluoroborates, used in the form of spray, on the development of common sorrel, gallant soldier and white goosefoot. The tests carried out also showed that the most toxic were the compounds with 1 and 3 carbon atoms. The phytotoxicity of tetrafluoroborates was positively correlated with the concentration of these compounds in the soil and was dependent on the genetic features of the genres and varieties of plants used in the experiment.

Applications and mechanisms of ionic liquids in whole-cell biotransformation

Ionic liquids (ILs), entirely composed of cations and anions, are liquid solvents at room temperature. They are interesting due to their low vapor pressure, high polarity and thermostability, and also for the possibility to fine-tune their physicochemical properties through modification of the chemical structures of their cations or anions. In recent years, ILs have been widely used in biotechnological fields involving whole-cell biotransformations of biodiesel or biomass, and organic compound synthesis with cells. Research studies in these fields have increased from the past decades and compared to the typical solvents, ILs are the most promising alternative solvents for cell biotransformations. However, there are increasing limitations and new challenges in whole-cell biotransformations with ILs. There is little understanding of the mechanisms of ILs' interactions with cells, and much remains to be clarified. Further investigations are required to overcome the drawbacks of their applications and to broaden their application spectrum. This work mainly reviews the applications of ILs in whole-cell biotransformations, and the possible mechanisms of ILs in microbial cell biotransformation are proposed and discussed.