Monitoring of environmental pollutants by bioluminescent bacteria

Recent advances in the development and applications of luminescent bacteria-based biosensors

Luminescent bacteria-based biosensors are widely used for fast and sensitive monitoring of food safety, water quality, and other environmental pollutions. Recent advancements in biomedical engineering technology have led to improved portability, integration, and intelligence of these biotoxicity assays. Moreover, genetic engineering has played a significant role in the development of recombinant luminescent bacterial biosensors, enhancing both detection accuracy and sensitivity. This review provides an overview of recent advances in the development and applications of novel luminescent bacteria-based biosensors, and future perspectives and challenges in the cutting-edge research, market translation, and practical applications of luminescent bacterial biosensing are discussed.

Assessing fresh water acute toxicity with Surface-Enhanced Raman Scattering (SERS)

It's well known that the toxicity of chemicals in the environment depends not only their concentrations, but more importantly, their bio-availability. Thus, the acute toxicity test of environmental water samples is of great importance in water quality evaluation. In this work, water acute toxicity was determined via SERS approach for the first time based on the reaction between Escherichia coli (E. coli) and p-benzoquinone (BQ). The E. coli was used as the subject of toxicity assay. Under normal conditions, the BQ molecules can be transformed into Hydroquinone (HQ) by the E. coli bacteria; subsequently, the BQ will continue to react with the resulting HQ to form Quinone hydroquinone (QHQ). This process could be impaired in the presence of many toxic chemicals. Bromide modified Ag NPs was then introduced for the highly sensitive SERS detection of the product (HQ and QHQ). Several key factors that may affect water acute toxicity evaluation have been explored, which include the initial BQ and E. coli concentration, the incubation time with BQ, and the sodium chloride concentration. Later, the established system was applied for the toxicity evaluation of Cu2+. It was found that the IC50 value of Cu2+ was 0.94 mg/L, which is superior compared with literature report. This study provides a promising SERS method for assessing acute toxicity in water bodies with high sensitivity and short detection time.

Effects of Endohedral Gd-Containing Fullerenols with a Different Number of Oxygen Substituents on Bacterial Bioluminescence

Gadolinium (Gd)-containing fullerenols are perspective agents for magnetic resonance imaging and cancer research. They combine the unique paramagnetic properties of Gd with solubility in water, low toxicity and antiradical activity of fullerenols. We compared the bioeffects of two Gd-containing fullerenols with a different number of oxygen groups-20 and 42: Gd@C82O20H14 and Gd@C82O42H32. The bioluminescent bacteria-based assay was applied to monitor the toxicity of fullerenols, bioluminescence was applied as a signal physiological parameter, and bacterial enzyme-based assay was used to evaluate the fullerenol effects on enzymatic intracellular processes. Chemiluminescence luminol assay was applied to monitor the content of reactive oxygen species (ROS) in bacterial and enzymatic media. It was shown that Gd@C82O42H32 and Gd@C82O20H14 inhibited bacterial bioluminescence at >10-1 and >10-2 gL-1, respectively, revealing a lower toxicity of Gd@C82O42H32. Low-concentration (10-3-10-1 gL-1) bacterial bioluminescence activation by Gd@C82O42H32 was observed, while this activation was not found under exposure to Gd@C82O20H14. Additional carboxyl groups in the structure of Gd@C82O42H32 were determined by infrared spectroscopy and confirmed by quantum chemical calculations. The groups were supposed to endow Gd@C82O42H32 with higher penetration ability through the cellular membrane, activation ability, lower toxicity, balancing of the ROS content in the bacterial suspensions, and lower aggregation in aqueous media.

Remediation Approaches to Reduce Hydrocarbon Contamination in Petroleum-Polluted Soil

Heavy metals pollution associated with oil spills has become a major concern worldwide. It is essential to break down these contaminants in the environment. In the environment, microbes have been used to detoxify and transform hazardous components. The process can function naturally or can be enhanced by adding nutrients, electron acceptors, or other factors. This study investigates some factors affecting hydrocarbon remediation technologies/approaches. Combinations of biological, chemical, and eco-toxicological techniques are used for this process while monitoring the efficacy of bacterial products and nutrient amendments to stimulate the biotransformation of contaminated soil. Different hydrocarbon removal levels were observed with bacterial augmentation (Beta proteobacterium and Rhodococcus ruber), exhibiting a total petroleum hydrocarbon (TPH) reduction of 61%, which was further improved to a 73% reduction using bacterial augmentation combined with nutrient amendment (nitrogen, potassium, and phosphorus). A heavy metal analysis of the polluted soils showed that the combination of nutrient and bacterial augmentation resulted in a significant reduction (p-value < 0.05) in lead, zinc, and barium. Toxicity testing also showed that a reduction of up to 50% was achieved using these remediation approaches.

Illuminating Progress: The Contribution of Bioluminescence to Sustainable Development Goal 6-Clean Water and Sanitation-Of the United Nations 2030 Agenda

The United Nations Agenda 2030 Sustainable Development Goal 6 (SDG 6) aims at ensuring the availability and sustainable management of water and sanitation. The routine monitoring of water contaminants requires accurate and rapid analytical techniques. Laboratory analyses and conventional methods of field sampling still require considerable labor and time with highly trained personnel and transport to a central facility with sophisticated equipment, which renders routine monitoring cumbersome, time-consuming, and costly. Moreover, these methods do not provide information about the actual toxicity of water, which is crucial for characterizing complex samples, such as urban wastewater and stormwater runoff. The unique properties of bioluminescence (BL) offer innovative approaches for developing advanced tools and technologies for holistic water monitoring. BL biosensors offer a promising solution by combining the natural BL phenomenon with cutting-edge technologies. This review provides an overview of the recent advances and significant contributions of BL to SDG 6, focusing attention on the potential use of the BL-based sensing platforms for advancing water management practices, protecting ecosystems, and ensuring the well-being of communities.

Water-Soluble Polymer Polyethylene Glycol: Effect on the Bioluminescent Reaction of the Marine Coelenterate Obelia and Coelenteramide-Containing Fluorescent Protein

The current paper considers the effects of a water-soluble polymer (polyethylene glycol (PEG)) on the bioluminescent reaction of the photoprotein obelin from the marine coelenterate Obelia longissima and the product of this bioluminescent reaction: a coelenteramide-containing fluorescent protein (CCFP). We varied PEG concentrations (0–1.44 mg/mL) and molecular weights (1000, 8000, and 35,000 a.u.). The presence of PEG significantly increased the bioluminescent intensity of obelin but decreased the photoluminescence intensity of CCFP; the effects did not depend on the PEG concentration or the molecular weight. The photoluminescence spectra of CCFP did not change, while the bioluminescence spectra changed in the course of the bioluminescent reaction. The changes can be explained by different rigidity of the media in the polymer solutions affecting the stability of the photoprotein complex and the efficiency of the proton transfer in the bioluminescent reaction. The results predict and explain the change in the luminescence intensity and color of the marine coelenterates in the presence of water-soluble polymers. The CCFP appeared to be a proper tool for the toxicity monitoring of water-soluble polymers (e.g., PEGs).

Functionalized Magnetite Nanoparticles: Characterization, Bioeffects, and Role of Reactive Oxygen Species in Unicellular and Enzymatic Systems

The current study evaluates the role of reactive oxygen species (ROS) in bioeffects of magnetite nanoparticles (MNPs), such as bare (Fe3O4), humic acids (Fe3O4-HA), and 3-aminopropyltriethoxysilane (Fe3O4-APTES) modified MNPs. Mössbauer spectroscopy was used to identify the local surrounding for Fe atom/ions and the depth of modification for MNPs. It was found that the Fe3O4-HA MNPs contain the smallest, whereas the Fe3O4-APTES MNPs contain the largest amount of Fe2+ ions. Bioluminescent cellular and enzymatic assays were applied to monitor the toxicity and anti-(pro-)oxidant activity of MNPs. The contents of ROS were determined by a chemiluminescence luminol assay evaluating the correlations with toxicity/anti-(pro-)oxidant coefficients. Toxic effects of modified MNPs were found at higher concentrations (>10−2 g/L); they were related to ROS storage in bacterial suspensions. MNPs stimulated ROS production by the bacteria in a wide concentration range (10−15−1 g/L). Under the conditions of model oxidative stress and higher concentrations of MNPs (>10−4 g/L), the bacterial bioassay revealed prooxidant activity of all three MNP types, with corresponding decay of ROS content. Bioluminescence enzymatic assay did not show any sensitivity to MNPs, with negligible change in ROS content. The results clearly indicate that cell-membrane processes are responsible for the bioeffects and bacterial ROS generation, confirming the ferroptosis phenomenon based on iron-initiated cell-membrane lipid peroxidation.

Marine Bacteria under Low-Intensity Radioactive Exposure: Model Experiments

Radioactive contaminants create problems all over world, involving marine ecosystems, with their ecological importance increasing in the future. The review focuses on bioeffects of a series of alpha and beta emitting radioisotopes (americium-241, uranium-(235 + 238), thorium-232, and tritium) and gamma radiation. Low-intensity exposures are under special consideration. Great attention has been paid to luminous marine bacteria as representatives of marine microorganisms and a conventional bioassay system. This bioassay uses bacterial bioluminescence intensity as the main testing physiological parameter; currently, it is widely applied due to its simplicity and sensitivity. Dependences of the bacterial luminescence response on the exposure time and irradiation intensity were reviewed, and applicability of hormetic or threshold models was discussed. A number of aspects of molecular intracellular processes under exposure to low-intensity radiation were analyzed: (a) changes in the rates of enzymatic processes in bacteria with the bioluminescent system of coupled enzymatic reactions of NADH:FMN-oxidoreductase and bacterial luciferase taken as an example; (b) consumption of an intracellular reducer, NADH; (c) active role of reactive oxygen species; (d) repairing of the DNA damage. The results presented confirm the function of humic substances as natural radioprotectors.

Mediator Microbial Biosensor Analyzers for Rapid Determination of Surface Water Toxicity

Microbial mediator biosensors for surface water toxicity determination make it possible to carry out an early assessment of the environmental object’s quality without time-consuming standard procedures based on standard test-organisms, and provide broad opportunities for receptor element modifying depending on the required operational parameters analyzer. Four microorganisms with broad substrate specificity and nine electron acceptors were used to form a receptor system for toxicity assessment. Ferrocene was the most effective mediator according to its high rate constant of interaction with the microorganisms (0.33 ± 0.01 dm3/(g × s) for yeast Saccharomyces cerevisiae). Biosensors were tested on samples containing four heavy metal ions (Cu2+, Zn2+, Pb2+, Cd2+), two phenols (phenol and p-nitrophenol), and three natural water samples. The «ferrocene- Escherichia coli» and «ferrocene-Paracoccus yeei, E. coli association» systems showed good operational stability with a relative standard deviation of 6.9 and 7.3% (14 measurements) and a reproducibility of 7 and 5.2% using copper (II) ions as a reference toxicant. Biosensor analysis with these systems was shown to highly correlate with the results of the standard method using Chlorella algae as a test object. Developed biosensors allow for a valuation of the polluted natural water’s impact on the ecosystem via an assessment of the influence on bacteria and yeast in the receptor system. The systems could be used in toxicological monitoring of natural waters.

Bioluminescent Dinoflagellates as a Bioassay for Toxicity Assessment

Dinoflagellates bioluminescence mechanism depends upon a luciferin–luciferase reaction that promotes blue light emission (480 nm) in specialized luminogenic organelles called scintillons. The scintillons contain luciferin, luciferase and, in some cases, a luciferin-binding protein (LBP), which prevents luciferin from non-enzymatic oxidation in vivo. Even though dinoflagellate bioluminescence has been studied since the 1950s, there is still a lack of mechanistic understanding on whether the light emission process involves a peroxidic intermediate or not. Still, bioassays employing luminous dinoflagellates, usually from Gonyaulax or Pyrocystis genus, can be used to assess the toxicity of metals or organic compounds. In these dinoflagellates, the response to toxicity is observed as a change in luminescence, which is linked to cellular respiration. As a result, these changes can be used to calculate a percentage of light inhibition that correlates directly with toxicity. This current approach, which lies in between fast bacterial assays and more complex toxicity tests involving vertebrates and invertebrates, can provide a valuable tool for detecting certain pollutants, e.g., metals, in marine sediment and seawater. Thus, the present review focuses on how the dinoflagellates bioluminescence can be applied to evaluate the risks caused by contaminants in the marine environment.

Droplet Microfluidic Device for Chemoenzymatic Sensing

The rapid detection of pollutants in water can be performed with enzymatic probes, the catalytic light-emitting activity of which decreases in the presence of many types of pollutants. Herein, we present a microfluidic system for continuous chemoenzymatic biosensing that generates emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN–oxidoreductase) with substrates required for the reaction. The developed chip generates “water-in-oil” emulsion droplets with a volume of 0.1 μL and a frequency of up to 12 drops per minute as well as provides the efficient mixing of reagents in droplets and their distancing. The bioluminescent signal from each individual droplet was measured by a photomultiplier tube with a signal-to-noise ratio of up to 3000/1. The intensity of the luminescence depended on the concentration of the copper sulfate with the limit of its detection of 5 μM. It was shown that bioluminescent enzymatic reactions could be carried out in droplet reactors in dispersed streams. The parameters and limitations required for the bioluminescent reaction to proceed were also studied. Hereby, chemoenzymatic sensing capabilities powered by a droplet microfluidics manipulation technique may serve as the basis for early-warning online water pollution systems.

Current technologies and future perspectives for the treatment of complex petroleum refinery wastewater: A review

Petroleum refinery wastewater (PRW) is a complex mixture of hydrocarbons, sulphides, ammonia, oils, suspended and dissolved solids, and heavy metals. As these pollutants are toxic and recalcitrant, it is essential to address the above issue with efficient, economical, and eco-friendly technologies. In this review, initially, an overview of the characteristics of wastewater discharged from different petroleum refinery units is discussed. Further, various pre-treatment and post-treatment strategies for complex PRW are introduced. A segregated approach has been proposed to treat the crude desalting, sour, spent caustic, and oily wastewater of petroleum refineries. The combined systems (e.g., ozonation + moving bed biofilm reactor and photocatalysis + packed bed biofilm reactor) for the treatment of low biodegradability index wastewater (BOD₅/COD < 0.2) were discussed to construct a perspective map and implement the proposed system efficiently. The economic, toxicity, and biodegradability aspects are also introduced, along with research gaps and future scope.

Toxicity monitoring of solvents, hydrocarbons, and heavy metals using statistically optimized model of luminous Vibrio sp. 6HFE

Background

The utilization of bioluminescent bacteria in environmental monitoring of water contaminates considers being a vital and powerful approach. This study aimed to isolate, optimize, and apply luminescent bacteria for toxicity monitoring of various toxicants in wastewater.

Results

On the basis of light intensity, strain Vibrio sp. 6HFE was initially selected, physiologically/morphologically characterized, and identified using the 16SrDNA gene. The luminescence production was further optimized by employing statistical approaches (Plackett-Burman design and central composite design). The maximum bioluminescence intensity recorded 1.53 × 10⁶ CPS using optimized medium containing (g/L), yeast extract (0.2g), CaCl₂ (4.0), MgSO₄ (0.1), and K₂HPO₄ (0.1) by 2.3-fold increase within 1h. The harnessing of Vibrio sp. 6HFE as a bioluminescent reporter for toxicity of organic solvents was examined using a bioluminescence inhibition assay. According to IC₅₀ results, the toxicity order of such pollutants was chloroform > isoamyl > acetic acid > formamide > ethyl acetate > acetonitrile > DMSO > acetone > methanol. However, among eight heavy metals tested, the bioluminescence was most sensitive to Ag⁺ and Hg⁺ and least sensitive to Co²⁺ and Ni²⁺. Additionally, the bioluminescence was inhibited by benzene, catechol, phenol, and penta-chlorophenol at 443.1, 500, 535.1, and 537.4 ppm.

Conclusion

Vibrio sp. 6HFE succeeded in pollution detection at four different environmental and wastewater samples revealing its efficiency in ecotoxicity monitoring.

From speciation to toxicity: Using a "Two-in-One" whole-cell bioreporter approach to assess harmful effects of Cd and Pb

Due to the sheer number of contaminated sites, bioavailability-based measurement and modeling of toxicity is used to triage response; despite advances, both remain relatively cumbersome. Cadmium (Cd) and lead (Pb) are two of the most toxic and globally prevalent pollutants, disproportionately impacting disadvantaged communities. Here we demonstrate the use of high throughput lights-on bioreporter technology to measure both speciation and toxicity. The organism's response is fit-for-purpose to parameterize the Biotic Ligand Model used in risk assessment of aquatic ecotoxicity and setting environmental Water Quality Criteria. Toxicity endpoints for analogous Cd and Pb models reported in literature average 71st and 44th rank-percentile sensitivity of Genus Mean Acute Values for acute toxicity (i.e., insensitive) in comparison to the bioreporter, the unique dual-mode measurement ability of which can predict toxicity endpoints from below the 5th percentile up to the 50th rank-percentile. These results are extensible to other reporters, paving the way to cost-efficient environmental risk assessment of aquatic ecotoxicity for a wide range of priority toxic pollutants.

Bioluminescence Color-Tuning Firefly Luciferases: Engineering and Prospects for Real-Time Intracellular pH Imaging and Heavy Metal Biosensing

Firefly luciferases catalyze the efficient production of yellow-green light under normal physiological conditions, having been extensively used for bioanalytical purposes for over 5 decades. Under acidic conditions, high temperatures and the presence of heavy metals, they produce red light, a property that is called pH-sensitivity or pH-dependency. Despite the demand for physiological intracellular biosensors for pH and heavy metals, firefly luciferase pH and metal sensitivities were considered drawbacks in analytical assays. We first demonstrated that firefly luciferases and their pH and metal sensitivities can be harnessed to estimate intracellular pH variations and toxic metal concentrations through ratiometric analysis. Using Macrolampis sp2 firefly luciferase, the intracellular pH could be ratiometrically estimated in bacteria and then in mammalian cells. The luciferases of Macrolampis sp2 and Cratomorphus distinctus fireflies were also harnessed to ratiometrically estimate zinc, mercury and other toxic metal concentrations in the micromolar range. The temperature was also ratiometrically estimated using firefly luciferases. The identification and engineering of metal-binding sites have allowed the development of novel luciferases that are more specific to certain metals. The luciferase of the Amydetes viviani firefly was selected for its special sensitivity to cadmium and mercury, and for its stability at higher temperatures. These color-tuning luciferases can potentially be used with smartphones for hands-on field analysis of water contamination and biochemistry teaching assays. Thus, firefly luciferases are novel color-tuning sensors for intracellular pH and toxic metals. Furthermore, a single luciferase gene is potentially useful as a dual bioluminescent reporter to simultaneously report intracellular ATP and/or luciferase concentrations luminometrically, and pH or metal concentrations ratiometrically, providing a useful tool for real-time imaging of intracellular dynamics and stress.

Microalgae Peptide-Stabilized Gold Nanoparticles as a Versatile Material for Biomedical Applications

Microalgae peptides have many medical and industrial applications due to their functional properties. However, the rapid degradation of peptides not naturally present in biological samples represents a challenge. A strategy to increase microalgae peptide stability in biological samples is to use carriers to protect the active peptide and regulate its release. This study explores the use of gold nanoparticles (AuNPs) as carriers of the Chlorella microalgae peptide (VECYGPNRPQF). The potential of these peptide biomolecules as stabilizing agents to improve the colloidal stability of AuNPs in physiological environments is also discussed. Spectroscopic (UV-VIS, DLS) and Microscopic (TEM) analyses confirmed that the employed modification method produced spherical AuNPs by an average 15 nm diameter. Successful peptide capping of AuNPs was confirmed with TEM images and FTIR spectroscopy. The stability of the microalgae peptide increased when immobilized into the AuNPs surface, as confirmed by the observed thermal shifts in DSC and high zeta-potential values in the colloidal solution. By optimizing the synthesis of AuNPs and tracking the conferred chemical properties as AuNPs were modified with the peptide via various alternative methods, the synthesis of an effective peptide-based coating system for AuNPs and drug carriers was achieved. The microalgae peptide AuNPs showed lower ecotoxicity and better viability than the regular AuNPs.

ECORISK2050: An Innovative Training Network for predicting the effects of global change on the emission, fate, effects, and risks of chemicals in aquatic ecosystems

By 2050, the global population is predicted to reach nine billion, with almost three quarters living in cities. The road to 2050 will be marked by changes in land use, climate, and the management of water and food across the world. These global changes (GCs) will likely affect the emissions, transport, and fate of chemicals, and thus the exposure of the natural environment to chemicals. ECORISK2050 is a Marie Skłodowska-Curie Innovative Training Network that brings together an interdisciplinary consortium of academic, industry and governmental partners to deliver a new generation of scientists, with the skills required to study and manage the effects of GCs on chemical risks to the aquatic environment. The research and training goals are to: (1) assess how inputs and behaviour of chemicals from agriculture and urban environments are affected by different environmental conditions, and how different GC scenarios will drive changes in chemical risks to human and ecosystem health; (2) identify short-to-medium term adaptation and mitigation strategies, to abate unacceptable increases to risks, and (3) develop tools for use by industry and policymakers for the assessment and management of the impacts of GC-related drivers on chemical risks. This project will deliver the next generation of scientists, consultants, and industry and governmental decision-makers who have the knowledge and skillsets required to address the changing pressures associated with chemicals emitted by agricultural and urban activities, on aquatic systems on the path to 2050 and beyond.

Endohedral Gd-Containing Fullerenol: Toxicity, Antioxidant Activity, and Regulation of Reactive Oxygen Species in Cellular and Enzymatic Systems

The Gd-containing metallofullerene derivatives are perspective magnetic resonance imaging contrast agents. We studied the bioeffects of a water-soluble fullerene derivative, gadolinium-endohedral fullerenol, with 40−42 oxygen groups (Gd@Fln). Bioluminescent cellular and enzymatic assays were applied to monitor toxicity and antioxidant activity of Gd@Fln in model solutions; bioluminescence was applied as a signaling physiological parameter. The Gd@Fln inhibited bioluminescence at high concentrations (>2·10−1 gL−1), revealing lower toxicity as compared to the previously studied fullerenols. Efficient activation of bioluminescence (up to almost 100%) and consumption of reactive oxygen species (ROS) in bacterial suspension were observed under low-concentration exposure to Gd@Fln (10−3−2·10−1 gL−1). Antioxidant capability of Gd@Fln was studied under conditions of model oxidative stress (i.e., solutions of model organic and inorganic oxidizers); antioxidant coefficients of Gd@Fln were determined at different concentrations and times of exposure. Contents of ROS were evaluated and correlations with toxicity/antioxidant coefficients were determined. The bioeffects of Gd@Fln were explained by hydrophobic interactions, electron affinity, and disturbing of ROS balance in the bioluminescence systems. The results contribute to understanding the molecular mechanism of “hormetic” cellular responses. Advantages of the bioluminescence assays to compare bioeffects of fullerenols based on their structural characteristics were demonstrated.

Tritium: Doses and Responses of Aquatic Living Organisms (Model Experiments)

Tritium is a byproduct of many radiochemical reactions in the nuclear industry, and its effects on aquatic organisms, particularly low-dose effects, deserve special attention. The low-dose effects of tritium on aquatic microbiota have been intensively studied using luminous marine bacteria as model microorganisms. Low-dose physiological activation has been demonstrated and explained by the signaling role of reactive oxygen species through the “bystander effect” in bacterial suspensions. The activation of microbial functions in natural reservoirs by low tritium concentrations can cause unpredictable changes in food chains and imbalances in the natural equilibrium. The incorporation of tritium from the free form into organically bound compounds mainly occurs in the dark and at a temperature of 25 °C. When tritium is ingested by marine animals, up to 56% of tritium is accumulated in the muscle tissue and up to 36% in the liver. About 50% of tritium in the liver is bound in non-exchangeable forms. Human ingestion of water and food products contaminated with background levels of tritium does not significantly contribute to the total dose load on the human body.

A two-step bioluminescence assay for optimizing antibacterial coating of hollow-fiber membranes with polydopamine in an integrative approach

Pure-water filtration membranes are often fouled by bacterial biofilms. Antibacterial coatings for preventing biofilm formation on such membranes should not rely on leaching of inhibiting compounds but should only be effective on surface contact. Certified assays for antibacterial coatings do not sufficiently exclude leaching effects and involve nutrient-rich cultivation media that do not correspond to conditions in pure-water systems. In this study, a two-step bioluminescence assay was developed for optimizing an antibacterial coating of PES/PVP ultrafiltration hollow-fiber membranes with a polydopamine as a sustainable, bio-inspired material for preventing bacterial biofilm formation. In the first step, leaching of the antimicrobial coating was analyzed by a bioluminescence assay with supernatants generated by washing coated membranes. In the second step, bioluminescence of bacterial biofilms on coated and uncoated membranes was measured using a nutrient-poor medium resembling site-specific conditions. Based on this bioluminescence assay, an optimized protocol for the coating process could be established by acidic polymerization of dopamine using 2 g/L sodium periodate and 4 g/L dopamine at 40 °C for 20 min reaction time. With coatings produced in this way, bioluminescence was reduced on coated membranes only while the corresponding supernatants exhibited no inhibitory effects.

Vertical profile and assessment of soil pollution from a typical coking plant by suspect screening and non-target screening using GC/QTOF-MS

A comprehensive workflow for suspect screening and non-target screening with gas chromatography coupled with quadrupole time-of-flight mass spectrometry (GC/QTOF-MS) was used to characterize the pollution characteristics of soil samples in a typical coking plant in China. Suspect screening confirmed 57 chemicals including PAHs, alkyl PAHs, and phthalates contained in high-resolution personal compound database and library (PCDL). Non-target screening detected 88 chemicals from soil samples in the NIST 17 library. A total of 122 chemicals were screened in soil samples, and many of them were of emerging concern. Their presence in the soil obtained from coking operations has been underestimated, such as the oxygenated PAHs (naphtho[2,1-b]furan and 9H-fluoren-9-one), and the alkyl biphenyls compounds (4,4'-dimethylbiphenyl, 3,3'-dimethylbiphenyl, 4-methyl-1,1'-biphenyl and 2,2',5,5'-tetramethyl-1,1'-biphenyl). Toxicity assays by luminescent bacteria proved that the extracts from soil samples at different depths showed varying toxicity to V. qinghaiensis sp.-Q67. Soil extracts from a depth of 20-40 cm exhibited the greatest toxicity to luminescent bacteria compared with the other six-layered soil samples, which was correlated with the number of detectable pollutants and total organic carbon content. This study provided a screening method for suspect and non-target contaminants in urban industrial soil sites, which was important in identifying localized contamination sources.

Adaptation of a Bacterial Bioluminescent Assay to Monitor Bioeffects of Gold Nanoparticles

Our current study aimed to adapt a bioluminescent bacteria-based bioassay to monitor the bioeffects of gold nanoparticles (AuNPs). Luminous marine bacteria Photobacterium phosphoreum and AuNPs modified with polyvinylpyrrolidone were employed; low-concentration (≤10−3 g/L) bioeffects of AuNPs were studied. Bioluminescence intensity was used as an indicator of physiological activity in bacteria. Two additional methods were used: reactive oxygen species (ROS) content was estimated with a chemiluminescent luminol method, and bacterial size was monitored using electron microscopy. The bacterial bioluminescent response to AuNPs corresponded to the “hormesis” model and involved time-dependent bioluminescence activation, as well as a pronounced increase in the number of enlarged bacteria. We found negative correlations between the time courses of bioluminescence and the ROS content in bacterial suspensions, demonstrating the relationship between bioluminescence activation and bacterial ROS consumption. The combined effects of AuNPs and a beta-emitting radionuclide, tritium, revealed suppression of bacterial bioluminescent activity (as compared to their individual effects) and a reduced percentage of enlarged bacteria. Therefore, we demonstrated that our bacteria-based bioluminescence assay is an appropriate tool to study the bioeffects of AuNPs; the bioeffects can be further classified within a unified framework for rapid bioassessment.

Development of Cellular and Enzymatic Bioluminescent Assay Systems to Study Low-Dose Effects of Thorium

Thorium is one of the most widespread radioactive elements in natural ecosystems, along with uranium, it is the most important source of nuclear energy. However, the effects of thorium on living organisms have not been thoroughly studied. Marine luminescent bacteria and their enzymes are optimal bioassays for studying low-dose thorium exposures. Luminescent bioassays provide a quantitative measure of toxicity and are characterized by high rates, sensitivity, and simplicity. It is known that the metabolic activity of bacteria is associated with the production of reactive oxygen species (ROS). We studied the effects of thorium-232 (10-11-10-3 M) on Photobacterium phosphoreum and bacterial enzymatic reactions; kinetics of bacterial bioluminescence and ROS content were investigated in both systems. Bioluminescence activation was revealed under low-dose exposures (<0.1 Gy) and discussed in terms of "radiation hormesis". The activation was accompanied by an intensification of the oxidation of a low-molecular reducer, NADH, during the enzymatic processes. Negative correlations were found between the intensity of bioluminescence and the content of ROS in bacteria and enzyme systems; an active role of ROS in the low-dose activation by thorium was discussed. The results contribute to radioecological potential of bioluminescence techniques adapted to study low-intensity radioactive exposures.

Effects of water produced by oil segment on aquatic organisms after treatment using advanced oxidative processes

The water produced (PW) by the petroleum industry is a potential contaminant to aquatic biota, due to its complex mixture that may contain polycyclic aromatic hydrocarbons (PAHs), organic chemical compounds, including benzene, toluene, ethylbenzene and xylene (BTEX), metals and other components that are known to be toxic. The aim of this investigation was to examine the acute toxicity produced by a PW sample in aquatic organisms Vibrio fischeri and Daphnia similis prior to and after 4 treatments using advanced oxidative processes such as photocatalysis, photoelectrocatalysis, ozonation and photoelectrocatalytic ozonation. Data demonstrated that exposure to PW was toxic to both organisms, as evidenced by reduced luminescence in bacterium Vibrio fischeri and induced immobility in Daphnia similis. After treatment of PW with 4 different techniques, the PW remained toxic for both tested organisms. However, photoelectrocatalysis was more efficient in decreasing toxicity attributed to PW sample. Therefore, data demonstrate the importance of treating PW for later disposal in the environment in order to mitigate ecotoxicological impacts. Further photoelectrocatalysis appeared to be a promising tool for treating PW samples prior to disposal and exposure of aquatic ecosystems.

The Influence of Herbicides to Marine Organisms Aliivibrio fischeri and Artemia salina

The aim of this work was to determine the toxic effect of the most used herbicides on marine organisms, the bacterium Aliivibrio fischeri, and the crustacean Artemia salina. The effect of these substances was evaluated using a luminescent bacterial test and an ecotoxicity test. The results showed that half maximal inhibitory concentration for A. fischeri is as follows: 15minIC50 (Roundup® Classic Pro) = 236 μg·L-1, 15minIC50 (Kaput® Premium) = 2475 μg·L-1, 15minIC50 (Banvel® 480 S) = 2637 μg·L-1, 15minIC50 (Lontrel 300) = 7596 μg·L-1, 15minIC50 (Finalsan®) = 64 μg·L-1, 15minIC50 (glyphosate) = 7934 μg·L-1, 15minIC50 (dicamba) = 15,937 μg·L-1, 15minIC50 (clopyralid) = 10,417 μg·L-1, 15minIC50 (nonanoic acid) = 16,040 μg·L-1. Median lethal concentrations for A. salina were determined as follows: LC50 (Roundup® Classic Pro) = 18 μg·L-1, LC50 (Kaput® Premium) = 19 μg·L-1, LC50 (Banvel® 480 S) = 2519 μg·L-1, LC50 (Lontrel 300) = 1796 μg·L-1, LC50 (Finalsan®) = 100 μg·L-1, LC50 (glyphosate) = 811 μg·L-1, LC50 (dicamba) = 3705 μg·L-1, LC50 (clopyralid) = 2800 μg·L-1, LC50 (nonanoic acid) = 7493 μg·L-1. These findings indicate the need to monitor the herbicides used for all environmental compartments.

In vitro toxicity of indoor and outdoor PM10 from residential wood combustion

Particulate matter with aerodynamic diameter < 10 μm (PM₁₀) was collected, indoors and outdoors, when wood burning appliances (open fireplace and woodstove) were in operation. The PM₁₀ ecotoxicity was assessed with the Vibrio fischeri bioluminescence inhibition assay, while the cytotoxicity was evaluated by the WST-8 and lactate dehydrogenase (LDH) release assays using A549 cells. Extracts of PM₁₀-bound polycyclic aromatic hydrocarbons (PAH) were tested for their mutagenicity through the TA98 and TA100 Ames test. The bioluminescent inhibition assay revealed that indoor particles released from the fireplace were the most toxic. Indoors, the reduction in A549 cell metabolic activity was over two times higher for the fireplace in comparison with the woodstove (32 ± 3.2% and 72 ± 7.6% at the highest dose, respectively). Indoor particles from the fireplace were found to induce greater cytotoxicity than the corresponding outdoor samples. Combined WST-8 and LDH results suggest that PM₁₀ exposure induce apoptotic cell death pathway in which the cell membrane integrity is maintained. Indoor and outdoor samples lacked direct and indirect mutagenic activity in any of the tester strains. For indoor-generated PM₁₀, organic carbon and PAH were significantly correlated with cell viability and bioluminescence reduction, suggesting a role of organic compounds in toxicity.

Investigations on the influence of energy source on time-dependent hormesis: A case study of sulfadoxine to Aliivibrio fischeri in different cultivation systems

Hormesis is a biphasic dose-response relationship featured by low-dose stimulation and high-dose inhibition. Although the hormetic phenomenon has been extensively studied over the past decades, there is little information regarding the influence of energy source on the occurrence of hormesis, especially the time-dependent one. In this study, to explore the role of cultivation system's energy source in time-dependent hormesis, the toxic dose-responses of Aliivibrio fischeri (A. fischeri) bioluminescence to Sulfadoxine (SDX) during 24 h were determined in four cultivation systems with different energy source conditions. The results indicated that the time-dependent hormetic effects were induced by SDX in all cultivation systems: SDX triggered hormetic phenomenon on the bioluminescence at each growth stage over 24 h in the cultivation systems with sufficient and insufficient energy source; due to the diauxic growth of A. fischeri under multiple energy source conditions, the hormetic effects of SDX gradually disappeared after the preferred energy source was used up. It was speculated that the inhibitory action of SDX was derived from its interaction with DHPS to impede the synthesis of proteins, and SDX bound with AC to upregulate the quorum sensing (QS) system to exhibit the stimulatory action. Comparing the time-dependent hormesis in each cultivation system, it was obtained that the energy source could impact the hourly maximum stimulatory rate, the EC₅₀ of SDX, and the time point that hormesis occurred, which might result from the influence of energy source on the stimulatory and inhibitory actions of SDX through regulating the metabolic system (individual level) and QS system (group level) of bacteria. This study clarifies the importance of energy source for hormesis occurrence, which may further promote the development of hormesis.

Comparison of Joint Effect of Acute and Chronic Toxicity for Combined Assessment of Heavy Metals on Photobacterium sp.NAA-MIE

Predicting the crucial effect of single metal pollutants against the aquatic ecosystem has been highly debatable for decades. However, dealing with complex metal mixtures management in toxicological studies creates a challenge, as heavy metals may evoke greater toxicity on interactions with other constituents rather than individually low acting concentrations. Moreover, the toxicity mechanisms are different between short term and long term exposure of the metal toxicant. In this study, acute and chronic toxicity based on luminescence inhibition assay using newly isolated Photobacterium sp.NAA-MIE as the indicator are presented. Photobacterium sp.NAA-MIE was exposed to the mixture at a predetermined ratio of 1:1. TU (Toxicity Unit) and MTI (Mixture Toxic Index) approach presented the mixture toxicity of Hg²⁺ + Ag⁺, Hg²⁺ + Cu²⁺, Ag⁺ + Cu²⁺, Hg²⁺ + Ag⁺ + Cu²⁺, and Cd²⁺ + Cu²⁺ showed antagonistic effect over acute and chronic test. Binary mixture of Cu²⁺ + Zn²⁺ was observed to show additive effect at acute test and antagonistic effect at chronic test while mixture of Ni²⁺ + Zn²⁺ showing antagonistic effect during acute test and synergistic effect during chronic test. Thus, the strain is suitable and their use as bioassay to predict the risk assessment of heavy metal under acute toxicity without abandoning the advantage of chronic toxicity extrapolation.

Toxicity and Antioxidant Activity of Fullerenol C60,70 with Low Number of Oxygen Substituents

Fullerene is a nanosized carbon structure with potential drug delivery applications. We studied the bioeffects of a water-soluble fullerene derivative, fullerenol, with 10-12 oxygen groups (F10-12); its structure was characterized by IR and XPS spectroscopy. A bioluminescent enzyme system was used to study toxic and antioxidant effects of F10-12 at the enzymatic level. Antioxidant characteristics of F10-12 were revealed in model solutions of organic and inorganic oxidizers. Low-concentration activation of bioluminescence was validated statistically in oxidizer solutions. Toxic and antioxidant characteristics of F10-12 were compared to those of homologous fullerenols with a higher number of oxygen groups:F24-28 and F40-42. No simple dependency was found between the toxic/antioxidant characteristics and the number of oxygen groups on the fullerene’s carbon cage. Lower toxicity and higher antioxidant activity of F24-28 were identified and presumptively attributed to its higher solubility. An active role of reactive oxygen species (ROS) in the bioeffects of F10-12 was demonstrated. Correlations between toxic/antioxidant characteristics of F10-12 and ROS content were evaluated. Toxic and antioxidant effects were related to the decrease in ROS content in the enzyme solutions. Our results reveal a complexity of ROS effects in the enzymatic assay system.

Open-source all-in-one LabToGo Office Chromatography

Print and media technologies were used uncommonly in the field of chromatography and explored in application to create a miniaturized all-in-one LabToGo system. This novel research field termed Office Chromatography (OC) uses additive manufacturing in terms of 3D printing of operational parts as well as open-source hard- and software. The OCLab2 presented here has been considerably extended in its functionalities. For inkjet printing of solutions, a newly designed printhead was manufactured controlled by a self-constructed ink-jet board, allowing to check the nozzles' resistance heating circuit. Plate heating was newly integrated, especially favorable for the demonstrated application of higher volumes of aqueous samples. The UV/Vis/FLD plate images were captured by a Raspberry Pi V2 camera module under illumination by novel light emitting diodes (LEDs) for highly selective RGBW color (Vis), UVC 278-nm (UV) and UVA 366-nm (FLD) detection, installed in a newly created miniature cabinet to protect from extraneous light. The spectral separation of differently colored food dyes was achieved by the fully addressable driver controlled RGBW LEDs. The software was newly written in R to speed-up the processes, supported by the new Raspberry Pi 4B computer with 4 GB RAM. The analysis of Stevia leaves for steviol glycosides yielded results comparable to the status quo. Different water samples were analyzed for bioactive compounds. Thereby, compounds of general cytotoxicity were effect-directed detected by bioluminescent A. fischeri bacteria. It allowed the bioanalytical screening for potential risks in tap water, surface waters, rain water, landfill leachates and biogas slurries.

Tracking gene expression, metabolic profiles, and biochemical analysis in the halotolerant basidiomycetous yeast Rhodotorula mucilaginosa EXF-1630 during benzo[a]pyrene and phenanthrene biodegradation under hypersaline conditions

Polyaromatic phenanthrene (Phe) and benzo[a]pyrene (BaP) are highly toxic, mutagenic, and carcinogenic contaminants widely dispersed in nature, including saline environments. Polyextremotolerant Rhodotorula mucilaginosa EXF-1630, isolated from Arctic sea ice, was grown on a huge concentration range -10 to 500 ppm- of Phe and BaP as sole carbon sources at hypersaline conditions (1 M NaCl). Selected polycyclic aromatic hydrocarbons (PAHs) supported growth as well as glucose, even at high PAH concentrations. Initially, up to 40% of Phe and BaP were adsorbed, followed by biodegradation, resulting in 80% removal in 10 days. While extracellular laccase, peroxidase, and un-specific peroxygenase activities were not detected, NADPH-cytochrome c reductase activity peaked at 4 days. The successful removal of PAHs and the absence of toxic metabolites were confirmed by toxicological tests on moss Physcomitrium patens, bacterium Aliivibrio fischeri, human erythrocytes, and pulmonary epithelial cells (A549). Metabolic profiles were determined at the midpoint of the biodegradation exponential phase, with added Phe and BaP (100 ppm) and 1 M NaCl. Different hydroxylated products were found in the culture medium, while the conjugative metabolite 1-phenanthryl-β-D-glucopyranose was detected in the medium and in the cells. Transcriptome analysis resulted in 870 upregulated and 2,288 downregulated transcripts on PAHs, in comparison to glucose. Genomic mining of 61 available yeast genomes showed a widespread distribution of 31 xenobiotic degradation pathways in different yeast lineages. Two distributions with similar metabolic capacities included black yeasts and mainly members of the Sporidiobolaceae family (including EXF-1630), respectively. This is the first work describing a metabolic profile and transcriptomic analysis of PAH degradation by yeast.

Rapid assessment of heavy metal toxicity using bioluminescent bacteria Photobacterium leiognathi strain GoMGm1

Several commercial test kits such as Microtox, LUMIStox, ToxAlert, Aboatox, and ToxScreen have been widely used for toxicity screening. Though this time saving assays offer excellent sensitivity, cost-effectiveness, and accuracy, these commercial assays are limited in terms of real-time monitoring in Indian coastal environment due to warmer temperatures. This necessitates the need to develop a rapid and accurate assay that can be effectively employed for real time monitoring with respect to heavy metals in the Indian coastal waters. With this objective, the present study was conducted by isolating an indigenous luminescent bacterium from the light organs of chordates Gazza minuta which showed higher luminescence in a wide range of temperatures. The isolate could grow well in the temperature of 30 ± 2 °C and withstand temperature up to 35 ± 2 °C. The isolated bacterium was identified as Photobacterium leiognathi GoMGm1 based on 16S rDNA and luxA gene sequences. The suitable growing medium was optimized using central composite rotational design (CCRD) method to obtain optimal growth and luminescence. The optimized medium exemplified the maximal growth and luminescence of P. leiognathi at OD_{600 nm} of 5.78 ± 0.12 and RLU of 12.49 ± 0.43. The isolate was used to assess the toxicity of several heavy metals. The IC₅₀ values of 0.0051, 1.13, 1.37, 3.1, and 6.68 mg L^-1 were observed for the Hg, Cr, Cu, Ni, and Zn, respectively, after 15 min of exposure. Results obtained from principal component analysis (PCA) displayed the present assay's compatibility with other luminescent bacterial assay and commercial Microtox™ assay. Thus, it would the right candidate as an early detection system for heavy metals in aquatic bodies in tropical countries. Schematic representation of the present study.

Evaluation use of bioaugmentation and biostimulation to improve degradation of sulfolane in artificial groundwater

Column systems were used to evaluate the effectiveness of different bioremediation methods (biostimulation (BS) and bioaugmentation (BA)) in treating sulfolane-contaminated groundwater. Batch test results confirmed that Cupriavidus sp. Y9 (Y9) was the most effective strain for BA. The optimal ratio of added native bacteria to Y9 was 10:3. The BA column adapted to a high sulfolane concentration (150 mg L^-1) more rapidly and had higher sulfolane removal efficiency (90%) than did the BS column. The change in the biotoxicity of sulfolane-contaminated groundwater upon bioremediation, according to a Microtox test, revealed decreases in the inhibition of the passing of light by the BS column and BS + BA column of 38% and 63%, respectively. These results reveal that combining BS with BA can reduce the biotoxicity of sulfolane. The column tests confirmed the most effective added bacterium in BA, the operating conditions for high-efficiency bioremediation, and possible problems in its future application. The results provide an important reference for the design of methods for the remediation of contaminated sites.

Glucocorticoids in Freshwaters: Degradation by Solar Light and Environmental Toxicity of the Photoproducts

The photodegradation process of seven glucocorticoids (GCs), cortisone (CORT), hydrocortisone (HCORT), betamethasone (BETA), dexamethasone (DEXA), prednisone (PRED), prednisolone (PREDLO) and triamcinolone (TRIAM) was studied in tap and river water at a concentration close to the environmental ones. All drugs underwent sunlight degradation according to a pseudo-first-order decay. The kinetic constants ranged from 0.00082 min⁻¹ for CORT to 0.024 min⁻¹ for PRED and PREDLO. The photo-generated products were identified by high-pressure liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The main steps of the degradation pathways were the oxidative cleavage of the chain 17 for CORT, HCORT and the rearrangement of the cyclohexadiene moiety for the other GCs. The acute and chronic toxicity of GCs and of their photoproducts was assessed by the V. fischeri and P.subcapitata inhibition assays. The bioassays revealed no significant differences in toxicity between the parent compounds and their photoproducts, but the two organisms showed different responses. All samples produced a moderate acute toxic effect on V. fisheri and no one in the chronic tests. On the contrary, evident hormesis or eutrophic effect was produced on the algae, especially for long-term contact.

Enzymatic Responses to Low-Intensity Radiation of Tritium

The present study considers a possible role of enzymatic reactions in the adaptive response of cells to the beta-emitting radionuclide tritium under conditions of low-dose exposures. Effects of tritiated water (HTO) on the reactions of bacterial luciferase and NAD(P)H:FMN-oxidoreductase, as well as a coupled system of these two reactions, were studied at radioactivity concentrations ≤ 200 MBq/L. Additionally, one of the simplest enzymatic reactions, photobiochemical proton transfer in Coelenteramide-containing Fluorescent Protein (CLM-FP), was also investigated. We found that HTO increased the activity of NAD(P)H:FMN-oxidoreductase at the initial stage of its reaction (by up to 230%); however, a rise of luciferase activity was moderate (<20%). The CLM-FP samples did not show any increase in the rate of the photobiochemical proton transfer under the exposure to HTO. The responses of the enzyme systems were compared to the 'hormetic' response of luminous marine bacterial cells studied earlier. We conclude that (1) the oxidoreductase reaction contributes significantly to the activation of the coupled enzyme system and bacterial cells by tritium, and (2) an increase in the organization level of biological systems promotes the hormesis phenomenon.

Bioluminescence goes portable: recent advances in whole-cell and cell-free bioluminescence biosensors

Recent advancements in synthetic biology, organic chemistry, and computational models have allowed the application of bioluminescence in several fields, ranging from well established methods for detecting microbial contamination to in vivo imaging to track cancer and stem cells, from cell-based assays to optogenetics. Moreover, thanks to recent technological progress in miniaturized and sensitive light detectors, such as photodiodes and imaging sensors, it is possible to implement laboratory-based assays, such as cell-based and enzymatic assays, into portable analytical devices for point-of-care and on-site applications. This review highlights some recent advances in the development of whole-cell and cell-free bioluminescence biosensors with a glance on current challenges and different strategies that have been used to turn bioassays into biosensors with the required analytical performance. Critical issues and unsolved technical problems are also highlighted, to give the reader a taste of this fascinating and challenging field.

Toxic response of the bacterium Vibrio fischeri to sodium lauryl ether sulphate residues in excavated soils

Sodium lauryl ether sulphate (SLES) is the main chemical component in several lubricant products used for soil conditioning in the mechanized excavation industry using Earth Pressure Balance-Tunnel Boring Machines. During the tunnelling process, huge amounts of excavated soil are produced and the SLES presence can affect the subsequent re-use of this material as a by-product. Currently, there is still no regulatory indication of reliable and sensitive bioassays for monitoring soil quality during the excavation process. The main objective of this work was to verify if the Vibrio fischeri screening test was suitable as a consistent and precautionary tool for this specific purpose. Firstly, the ecotoxicity (EC₂₀ and EC₅₀) of the SLES standard solution and three commercial products (SLES content from 10 to 50%) were evaluated to select the most environmental friendly product. Subsequently, soil samples from about 2 years of tunnelling in a real construction site, conditioned with the selected product, were evaluated for their environmental compatibility with the prescriptions of an Italian site-specific protocol. The latter established 2 mg/L as a threshold value for SLES concentration in soil water extracts and a no toxic response (≤20%) for the Vibrio fischeri test. The comparison of the bacterium bioluminescence inhibition values (%) with analytical determinations showed an ecotoxicity when SLES was >2 mg/L. The toxicity was directly related to SLES concentration, indicating that the V. fischeri test and the SLES analyses are suitable tools for assessing excavated soil as a by-product, ensuring its safe reuse in accordance with a green production process (circular economy).

Development of a high-throughput bioassay for screening of antibiotics in aquatic environmental samples

The goal of the present study was to select a Gram-positive (Gram+) and Gram-negative (Gram-) strain to measure antimicrobial activity in environmental samples, allowing high-throughput environmental screening. The sensitivity of eight pre-selected bacterial strains were tested to a training set of ten antibiotics, i.e. three Gram+ Bacillus subtilis strains with different read-outs, and five Gram- strains. The latter group consisted of a bioluminescent Allivibrio fischeri strain and four Escherichia coli strains, i.e. a wild type (WT) and three strains with a modified cell envelope to increase their sensitivity. The WT B. subtilis and an E. coli strain newly developed in this study, were most sensitive to the training set. This E. coli strain carries an open variant of an outer membrane protein combined with an inactivated multidrug efflux transport system. The assay conditions of these two strains were optimized and validated by exposure to a validation set of thirteen antibiotics with clinical and environmental relevance. The assay sensitivity ranged from the ng/mL to μg/mL range. The applicability of the assays for toxicological characterization of aquatic environmental samples was demonstrated for hospital effluent extract. A future application includes effect-directed analysis to identify yet unknown antibiotic contaminants or their transformation products.

Effects of Modified Magnetite Nanoparticles on Bacterial Cells and Enzyme Reactions

Current paper presents biological effects of magnetite nanoparticles (MNPs). "Relations of MNP' characteristics (zeta-potential and hydrodynamic diameters) with effects on bacteria and their enzymatic reactions were the main focus.". Photobacterium phosphoreum and bacterial enzymatic reactions were chosen as bioassays. Three types of MNPs were under study: bare Fe3O4, Fe3O4 modified with 3-aminopropyltriethoxysilane (Fe3O4/APTES), and humic acids (Fe3O4/HA). Effects of the MNPs were studied at a low concentration range (< 2 mg/L) and attributed to availability and oxidative activity of Fe3+, high negative surface charge, and low hydrodynamic diameter of Fe3O4/HA, as well as higher Fe3+ content in suspensions of Fe3O4/HA. Low-concentration suspensions of bare Fe3O4 provided inhibitory effects in both bacterial and enzymatic bioassays, whereas the MNPs with modified surface (Fe3O4/APTES and Fe3O4/HA) did not affect the enzymatic activity. Under oxidative stress (i.e., in the solutions of model oxidizer, 1,4-benzoquinone), MNPs did not reveal antioxidant activity, moreover, Fe3O4/HA demonstrated additional inhibitory activity. The study contributes to the deeper understanding of a role of humic substances and silica in biogeochemical cycling of iron. Bioluminescence assays, cellular and enzymatic, can serve as convenient tools to evaluate bioavailability of Fe3+ in natural dispersions of iron-containing nanoparticles, e.g., magnetite, ferrihydrite, etc.

Investigating the origins of acute and long-term toxicity posed by municipal wastewater using fractionation

It has been proven that the raw wastewater, secondary effluent and even reclaimed water may have toxic effects on aquatic organisms. In the present study, fractionation procedures combined with bioassays using luminescent bacteria were conducted to identify the fractions that contributed to the acute and long-term toxicity of municipal wastewater. Solid phase extraction was used to divide dissolved organic matter from the wastewater into three fractions, including non-polar, medium-polar and polar fraction. Among these fractions, although the acute toxicity of municipal wastewater was mainly caused by polar and medium-polar chemicals, the acute toxicity induced by the unit mass of the medium-polar fraction was the greatest. Using three kinds of resins, the organic substances in municipal wastewater were classified into six fractions, and the long-term toxicity of these fractions was further identified. The long-term toxicity of the hydrophobic neutrals, which were the primary toxic substances in raw wastewater, decreased after the conventional secondary biological treatment. Hydrophilic neutrals, which accounted for the majority of organic substances in the secondary effluent, were the main substances with long-term toxicity in the secondary effluent. The identification of fractions with acute and long-term toxicity in municipal wastewater is beneficial for further treatment to attenuate the ecotoxicity of wastewater before discharge into the aquatic environment.

Comprehensive depiction of novel heavy metal tolerant and EPS producing bioluminescent Vibrio alginolyticus PBR1 and V. rotiferianus PBL1 confined from marine organisms

The current study depicts the isolation of luminescent bacteria from fish and squid samples that were collected from Veraval fish harbour. From Indian mackerel, total 14 and from squid, total 23 bioluminescent bacteria were isolated using luminescence agar medium. Two bioluminescent bacteria with highest relative luminescence intensity PBR1 and PBL1 were selected. These two isolates were subjected to detailed biochemical characterization and were tested positive for 5 out of 13 biochemical tests. Furthermore, both PBR1 and PBL1 were able to ferment cellobiose, dextrose, fructose, galactose, maltose, mannose, sucrose and trehalose with acid production. Based on 16S rRNA partial gene sequence analysis, PBR1 was identified as Vibrio alginolyticus and PBL1 as V. rotiferianus. Antibiotic susceptibility test using paper-disc method showed that PBR1 and PBL1 were sensitive to chloramphenicol, ciprofloxacin, co-trimoxazole, gatifloxacin, levofloxacin, linezolid ad roxithromycin out of 18 antibiotics tested. Moreover, both strains were evaluated for their exopolysachharide (EPS) producing ability where PBR1 and PBL1 were able to yield 1.34 g% (w/v) and 2.45 g% (w/v) EPS respectively from 5 g% (v/v) sucrose concentration. Heavy metal toxicity assessment was carried out using agar well diffusion method with eight heavy metals and both the strains were sensitive to As(III), Cd(II), Ce(II), Cr(III), Cu(II), Hg(II) and while they showed resistance to Pb(II) and Sr(II). Based on these results, a study was conducted to demonstrate bio-removal of Pb and Sr by EPS of PBR1 and PBL1. Fourier transform infrared (FTIR) spectra revealed the functional groups of EPS involved in interaction with the heavy metals. Owing to the sensitivity for the remaining heavy metals, these bioluminescent bacteria can be used further for the development of luminescence-based biosensor.

Correlation of Oxidative Potential with Ecotoxicological and Cytotoxicological Potential of PM10 at an Urban Background Site in Italy

Exposure to atmospheric particulate matter (PM) has detrimental effects on health, but specific mechanisms of toxicity are still not fully understood. In recent years, there has been a growing evidence that oxidative stress is an important mechanism of toxicity; however, when acellular oxidative potential (OP) data are correlated with the outcomes of in vitro (or in vivo) toxicological tests there are contrasting results. In this work, an analysis of PM10 health effect indicators was done, using the acellular Dithiotreitol (DTT) assay to retrieve OPDTT, the Microtox® test on Vibrio fischeri bacterium to assess the ecotoxicological potential, and the in vitro MTT assay on the human cell line A549 to estimate the cytotoxicological potential. The objective was to evaluate the correlation among acellular OPDTT and the results from toxicological and ecotoxicological bioassays and how these health-related indicators are correlated with atmospheric PM10 concentrations collected at an urban background site in Southern Italy. Results indicated that both bioassays showed time-dependent and dose-dependent outcomes. Some samples presented significant ecotoxic and cytotoxic response and the correlation with PM10 concentration was limited suggesting that these health endpoints depend on PM10 chemical composition and not only on exposure concentrations. OPDTT showed a statistically significant correlation with PM10 concentrations. MTT and Microtox outcomes were not correlated suggesting that the two toxicological indicators are sensitive to different physical-chemical properties of PM10. Intrinsic oxidative potential OPDTTM (DTT activity normalised with PM10 mass) was correlated with mortality observed with MTT test (normalized with PM10 mass); however, it was not correlated with Microtox outcomes.

Monitoring of Low-Intensity Exposures via Luminescent Bioassays of Different Complexity: Cells, Enzyme Reactions, and Fluorescent Proteins

The current paper reviews the applications of luminescence bioassays for monitoring the results of low-intensity exposures which produce a stimulative effect. The impacts of radioactivity of different types (alpha, beta, and gamma) and bioactive compounds (humic substances and fullerenols) are under consideration. Bioassays based on luminous marine bacteria, their enzymes, and fluorescent coelenteramide-containing proteins were used to compare the results of the low-intensity exposures at the cellular, biochemical, and physicochemical levels, respectively. High rates of luminescence response can provide (1) a proper number of experimental results under comparable conditions and, therefore, proper statistical processing, with this being highly important for "noisy" low-intensity exposures; and (2) non-genetic, i.e., biochemical and physicochemical mechanisms of cellular response for short-term exposures. The results of cellular exposures were discussed in terms of the hormesis concept, which implies low-dose stimulation and high-dose inhibition of physiological functions. Dependencies of the luminescence response on the exposure time or intensity (radionuclide concentration/gamma radiation dose rate, concentration of the bioactive compounds) were analyzed and compared for bioassays of different organization levels.

Use of Cyanobacterial Luminescent Bioreporters to Report on the Environmental Impact of Metallic Nanoparticles

Due to their ecological relevance, low cost, and easy maintenance, cyanobacteria have been used for bioreporter development. In this study, a battery of cyanobacterial bioreporters has been used to assess the ecotoxicity of four highly used metallic nanoparticles (NPs). The toxicity of these NPs was tested using the bioreporter Nostoc CPB4337 (Anabaena CPB4337). As oxidative stress is a primary toxic mechanism of metallic NPs, cyanobacterial reactive oxygen species (ROS)-detecting bioreporters were used. Metallic NPs release metal ions, which contribute to their toxic effect and the formation of ROS, so a metal-detecting bioreporter was also used to detect the bioavailable metals. The results confirm that ROS production by NPs was due to the NPs per se and not by released free-ions, which in fact were almost undetectable. Although the metal-detecting bioreporter could not detect the dissolved metal ions, it was able to detect the metallic NPs themselves, indicating that this bioreporter may be useful to detect them in the environment. ROS production varied depending on the growth medium or environmental matrices conditions and on the NP type. This work demonstrated the different levels of ROS production by metallic NPs and the importance of nanotoxicology studies in real matrices.

A deep insight into the toxic mechanism for sulfonamides based on bacterial cell-cell communication

Sulfonamides (SAs), a kind of commonly used antibiotics, have been frequently detected in the environment. Due to their potential threat to the ecological environment, the toxicity of SAs to bacteria have been determined in depth, and the toxic mechanism is found to target dihydropteroate synthase (DHPS). However, other toxic mechanism may also exist for SAs, which is still unclear to us. In this paper, the toxic mechanism of sulfachloropyridazine (SCP, as a representative of SAs) was investigated thoroughly on Aliivibrio fischeri (A. fischeri) from the perspective of quorum sensing (QS). The results reveal that SCP may act on three signaling pathways, i.e., Pathway I, II and III, which triggers, maintains and destroys the homeostasis of A. fischeri respectively. In Pathway I, SCP changes the active form of LitR that regulates the expression of lux-related genes, inducing inhibition on bacterial growth while stimulation on luminescence; in Pathway II, SCP facilitates the production of C6HSL signaling molecules, maintaining the homeostasis in LitR and DHPS proteins; whereas in Pathway III, SCP typically combines with DHPS to inhibit the folate metabolism. This study can provide a deeper and more comprehensive understanding on the toxicity of SAs and help the environmental risk assessment of SAs.