Application of enzyme bioluminescence in ecology

Acute Osmotic and pH Shock to Bioluminescent Bacteria Is Reversible in Terms of Luminescence Response

Bioluminescence inhibition (BLI) measurements in bioluminescent bacteria (BB) is perceived as a potential qualitative and quantitative indicator of hazardous materials. Acute but minor fluctuations in osmolarity and pH do not affect the living systems significantly. However, significant BLI is observed from marine BB due to acute osmolarity or pH changes that may affect the bioassay sensitivity. Often, real samples have low pH and osmolarity, interfering with the hazard assessment based on the principles of BLI. This anomaly in BLI measurements may lead to false positives. Therefore, modifications in existing analytical methods to overcome such practical constraints are envisaged. In the present research, a marine BB was utilized to study the luminescence reversal effect when exposed to stressful environments such as hypotonic (deionized water), acidic (50 μM to 50 mM HCl), and 0.1-100 ppm of Hg(II) for 0-30 min. Postincubation, the calcium alginate immobilized bioluminescent bacteria (biophotonic beads) were transferred to Boss media to observe any luminescence enhancement. The results showed that osmotic shock and low-strength acidic environments (50 μM to 0.5 mM HCl) at specified incubation times were not detrimental to the biophonic beads regarding luminescence response.

The use of bioluminescent enzyme bioassay for the analysis of human saliva: Advantages and disadvantages

The purpose of the work was to find optimal conditions for bioluminescent enzymatic analysis of saliva (based on the use of NADH:FMN oxidoreductase + luciferase) and then to determine the biological effect of using bioluminescence assay of saliva to study the physiological state of the body under normal and pathological conditions. The saliva of snowboarders and students were studied in the "rest-training" model. The saliva of patients diagnosed with acute pharyngitis was examined in the "sick-healthy" model. Bioluminescence assay was performed with a lyophilized and immobilized bi-enzyme system using cuvette, plate, and portable luminometers. The concentrations of secretory immunoglobulin A (sIgA) and cortisol were determined by enzyme immunoassay, and the total protein content was measured by spectrophotometric method. The activity of the bioluminescent system enzymes increased as the amount and volume of saliva in the sample was decreased. The cuvette and plate luminometers were sensitive to changes in the luminescence intensity in saliva assay. Luminescence intensity correlated with the concentrations of sIgA and cortisol. The integrated bioluminescent index for saliva was reduced in the "rest-training" model and increased in the "sick-healthy" model. Thus, the non-invasive bioluminescent saliva analysis may be a promising tool for assessing the health of the population.

Coupling of NAD(P)H:FMN-oxidoreductase and luciferase from luminous bacteria in a viscous medium: Finding the weakest link in the chain

The study aims at revealing the mechanisms of the viscous medium effects on the kinetic features of NAD(P)H:FMN-oxidoreductase from luminous bacteria (Red), which are exhibited in a single enzyme assay and in coupling with bacterial luciferase (BLuc). Different concentrations of glycerol and sucrose were used to vary the medium viscosity. The activity of Red, alone and in the presence of BLuc, was analyzed, as well as BLuc activity in the presence of Red, whereas in the absence of BLuc, the Red activity was suppressed in viscous medium, and in the presence of BLuc, the increase in Red activity was observed at low glycerol concentrations (5-20 wt%). The interaction of glycerol and sucrose with Red substrates FMN and NADH was studied using absorption spectroscopy and molecular dynamics. Glycerol was found to form hydrogen bonds with the phosphate groups of the substrates, unlike sucrose. A mechanism for the activation of Red in the presence of BLuc in glycerol solutions through the acceleration of FMN reoxidation was proposed. Thus, it was concluded that, under the conditions used, the weakest link of the coupled enzyme system BLuc-Red in viscous medium is the FMN concentration, which depends on Red activity and the medium viscosity.

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.

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.

Set of Enzymatic Bioassays for Assessment of Soil Contamination

A concept of the comprehensive assessment of soil contamination is proposed. According to it, the conclusion regarding the presence of toxic substances in the analyzed sample is based on the inhibition of enzymatic reactions responsible for various functions of a living organism, such as luminescence, respiration, etc. These functions are taken as test functions in classical bioassays with the use of living objects (luminous bacteria, daphnia, algae, and others). The regularities of the impact of different classes of toxicants on the activity of particular enzymes or coupled oligo-enzyme chains have been established. These enzyme reactions are selected as potential test objects: markers of contamination. Three enzyme systems with the maximal sensitivity to different classes of toxicants have been chosen for the set of enzymatic bioassays: butyrylcholinesterase, NAD(P)H:FMN-oxidoreductase + luciferase, and lactate dehydrogenase + NAD(P)H:FMN-oxidoreductase + luciferase. The possibility to use enzymes instead of living organisms in the bioassay of natural complex systems has been shown.

NAD(P)H:FMN‑Oxidoreductase Functioning Under Macromolecular Crowding: In Vitro Modeling

The functioning of NAD(P)H:FMN‑oxidoreductase (Red) from Vibrio fischeri under conditions of macromolecular crowding (MMC) simulated in vitro by adding biopolymers (starch and gelatin) was studied. The dissociation rate constants and the activation energies of dissociation of Red to the subunits were calculated, and the process of denaturation of Red was analyzed. It is shown that the functioning of Red both under conditions of MMC and in diluted solutions is the same. This result refutes the common belief that the native conformation of enzymes in vivo is stabilized due to MMC as compared to the in vitro conditions.

Principles for Construction of Bioluminescent Enzyme Biotests for Analysis of Complex Media

In this study, we formulated the principles of designing bioluminescent enzyme tests for assessing the quality of complex media, which consist in providing the maximum sensitivity to potentially toxic chemicals at a minimal impact of uncontaminated complex media. The developed principles served as a basis for designing a new bioluminescent method for an integrated rapid assessment of chemical safety of fruits and vegetables, which is based on using the luminous bacteria enzymes (NAD(P)H:FMN oxidoreductase and luciferase) as a test system.

A Tale Of Two Luciferins: Fungal and Earthworm New Bioluminescent Systems

Bioluminescence, the ability of a living organism to produce light through a chemical reaction, is one of Nature's most amazing phenomena widely spread among marine and terrestrial species. There are various different mechanisms underlying the emission of "cold light", but all involve a small molecule, luciferin, that provides energy for light-generation upon oxidation, and a protein, luciferase, that catalyzes the reaction. Different species often use different proteins and substrates in the process, which suggests that the ability to produce light evolved independently several times throughout evolution. Currently, it is estimated that there are more than 30 different mechanisms of bioluminescence. Even though the chemical foundation underlying the bioluminescence phenomenon is by now generally understood, only a handful of luciferins have been isolated and characterized. Today, the known bioluminescence reactions are used as indispensable analytical tools in various fields of science and technology. A pressing need for new bioluminescent analytical techniques with a wider range of practical applications stimulates the search and chemical studies of new bioluminescent systems. In the past few years two such systems were unraveled: those of the earthworms Fridericia heliota and the higher fungi. The luciferins of these two systems do not share structural similarity with the previously known ones. This Account will survey structure elucidation of the novel luciferins and identification of their mechanisms of action. Fridericia luciferin is a key component of a novel ATP-dependent bioluminescence system. Structural studies were performed on 0.005 mg of natural substance and revealed its unusual extensively modified peptidic nature. Elucidation of Fridericia oxyluciferin revealed that oxidative decarboxylation of a lysine fragment of luciferin supplies energy for light generation, while a fluorescent CompX moiety remains intact and serves as a light emitter. Along with luciferin, a number of its natural analogs were found in the extracts of worm biomass. They occurred to be highly unusual modified peptides comprising a set of amino acids, including threonine, aminobutyric acid, homoarginine, unsymmetrical N,N-dimethylarginine and extensively modified tyrosine. These natural compounds represent a unique peptide chemistry found in terrestrial animals and raise novel questions concerning their biosynthetic origin. Also in this Account we discuss identification of the luciferin of higher fungi 3-hydroxyhispidin which is biosynthesized by oxidation of the precursor hispidin, a known fungal and plant secondary metabolite. Furthermore, it was shown that 3-hydroxyhispidin leads to bioluminescence in extracts from four diverse genera of luminous fungi, thus suggesting a common biochemical mechanism for fungal bioluminescence.

Antioxidant activity of humic substances via bioluminescent monitoring in vitro

This work considers antioxidant properties of natural detoxifying agents-humic substances (HS) in solutions of model inorganic and organic compounds of oxidative nature-complex salt K3[Fe(СN)6] and 1,4-benzoquinone. Bioluminescent system of coupled enzymatic reactions catalyzed by

NAD(P)H

FMN-oxidoreductase and bacterial luciferase was used as a bioassay in vitro to monitor toxicity of the oxidizer solutions. Toxicities of general and oxidative types were evaluated using bioluminescent kinetic parameters-bioluminescence intensity and induction period, respectively. Antioxidant activity of HS was attributed to their ability to decrease both general and oxidative toxicities; the HS antioxidant efficiency was characterized with detoxification coefficients D GT and D OxT, respectively. Dependencies of D GT and D OxT on HS concentration and time of preliminary incubation of the oxidizers with HS were demonstrated. The optimal conditions for detoxification of the oxidizers were >20-min incubation time and 0.5 × 10(-4) to 2 × 10(-4) M of HS concentration. The present study promotes application of the enzymatic luminescent bioassay to monitor toxicity of pollutants of oxidative nature in environmental and waste waters in remediation procedures.