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Introduction. Currently, the search for new antibacterial substances is an urgent task due to the growing resistance of pathogens to existing antibiotics. One of the key directions in this area is the expansion of scientific research of medicinal plants, as new sources of therapeutic agents. This article examines the possibility of using highly sensitive bioluminescent test bacteria for these purposes, which can quickly detect non-specific antimicrobial activity and can be adapted to highly effective pharmaceutical screening technologies.Aim. To study the applicability of bioluminescent bacteria for the analysis of the antibacterial activity of biologically active substances (BAS) of plant origin.Materials and methods. BAS quercetin, 8-hydroxyquinoline, gallic acid and thymoquinone, which are often found in medicinal plant raw materials and with which its antibacterial properties are associated, were used in the work. Bacteria with constitutive bioluminescence Aliivibrio fischeri F1 and Escherichia coli (pXen7), as well as recombinant bioreporter strains with inducible luminescence were used as test-objects: E. coli (pRecA-lux), E. coli (pColD-lux), reacting to nucleic acid damage; E. coli (pKatG-lux) and E. coli (pSoxS-lux), sensitive to oxidative stress.Results and discussion. It was found that the nonspecific antimicrobial activity of the studied BAS is manifested in the inhibition of bacterial bioluminescence of test-strains with constitutive glowing. It was noted that the marine test-bacteria A. fischeri F1 have significantly greater sensitivity to the action of BAS, compared with the recombinant strain of E. coli (pXen7). It has been shown that their inhibitory effect begins at concentrations of 2 mcg/ml, and bactericidal activity occurs at concentrations of more than 20 mcg/ml. The results obtained are compared with the data on MIC and MBC of gram(+) and gram(–) pathogens. The study of the induction of bioluminescence of recombinant bioreporter strains showed that the antibacterial effect of the BAS is accompanied by oxidative stress. Also, quercetin caused activation of luminescence in E. coli (pRecA-lux) and E. coli (pColD-lux), which may indicate its participation in damage to nucleic acids. Analysis of the induction factors of bioreporter strains indicates that the revealed mechanisms of antibacterial activity are not major, but may be of a secondary nature.Conclusion. It has been shown that the intensity of the glow of natural and recombinant bioluminescent bacteria can be an indicator of the antibacterial activity of BAS of natural origin. The high sensitivity of A. fischeri F1 bacteria to the action of substances such as quercetin, 8-hydroxyquinoline, gallic acid and thymoquinone has been shown. Considering that bioluminescence analysis is a quantitative instrumental method, it can be easily adapted for high-throughput pharmaceutical screening. It has been shown that the luminescence intensity of natural and recombinant bioluminescent bacteria can be an indicator of the antibacterial activity of BAS of natural origin. The high sensitivity of A. fischeri F1 to the action of substances such as quercetin, 8-hydroxyquinoline, gallic acid and thymoquinone has been established. Taking in an account that bioluminescent analysis is a quantitative instrumental method, it can be easily adapted for high-throughput pharmaceutical screening.

The light emitted by a luminescent bacterium serves as a unique native channel of information regarding the intracellular processes within the individual cell. In the presence of highly sensitive equipment, it is possible to obtain the distribution of bacterial culture cells by the intensity of light emission, which correlates with the amount of luciferase in the cells. When growing on rich media, the luminescence intensity of individual cells of brightly luminous strains of the luminescent bacteria Photobacterium leiognathi and Ph. phosporeum reaches 104–105 quanta/s. The signal of such intensity can be registered using sensitive photometric equipment. All experiments were carried out with bacterial clones (genetically homogeneous populations). A typical dynamics of luminous bacterial cells distributions with respect to intensity of light emission at various stages of batch culture growth in a liquid medium was obtained. To describe experimental distributions, a phenomenological model that links the light of a bacterial cell with the history of events at the molecular level was constructed. The proposed phenomenological model with a minimum number of fitting parameters (1.5) provides a satisfactory description of the complex process of formation of cell distributions by luminescence intensity at different stages of bacterial culture growth. This may be an indication that the structure of the model describes some essential processes of the real system. Since in the process of division all cells go through the stage of release of all regulatory molecules from the DNA molecule, the resulting distributions can be attributed not only to luciferase, but also to other proteins of constitutive (and not only) synthesis.

At the beginning of the paper, the level of necessary phenomenology of complex models is discussed. When working with complex systems, which of course include living organisms and ecological systems, it is necessary to use a phenomenological description. An illustration of the phenomenological approach is given, which captures the most significant general principles or patterns of interactions; the specific values of the parameters cannot be calculated from the first principles, but are determined empirically. An appropriate interpretation is also chosen empirically and pragmatically. However, in order to simulate a wider range of situations, it becomes necessary to lower the level of phenomenology, switch to a more detailed description of the system, introducing interaction between selected elements of the system. The requirements for a system model combining ecological, metabolic and genetic levels of cell culture description are formulated. A mathematical model of quorum sensing dynamics during the growth of batch culture of luminescent bacteria at different concentrations of the nutrient substrate has been developed. The model contains four blocks describing ecological, energy, quorum and luminescent aspects of bacterial culture growth. The model demonstrated good agreement with the experimental data obtained. When analyzing the model, three oddities in the behavior of the culture were noted, which presumably can change the idea of some processes taking place during the development of a culture of luminescent bacteria. The results obtained suggest the presence of some additional control system for the luminescent reaction via the synthesis pathways of FMN · Н2 or aliphatic aldehyde. In this case, the generalized description of the contribution of energy metabolism to luminescence only through ATP is too strong a simplification. As a result of comparing the model dynamics with the experiment, a discrepancy arose between the concentration of the substrate (peptone) measured in the experiment and its effective influence on the bacterial population growth. This discrepancy seems to indicate peptone is not the leading substrate, and growth is limited by nutrients contained in the yeast extract, the concentration of which did not change in these experiments. The discrepancies noted between the expectations and the results of experimental data processing, together with the assumptions about the causes of these discrepancies, set the direction for further experimental and theoretical studies of quorum sensing mechanisms in a culture of luminescent bacteria.

Introduction: Bioremediation has been shown to be an effective strategy for removing toxic pollutants from the environment, particularly organic chemicals such as petroleum hydrocarbons. This paper investigates the changes in toxicity of petroleum-contaminated soil as a result of microbial remediation processes.Methods: Changes in the ecotoxicity of the contaminated soil were examined using a plant, earthworm, enzyme activity and luminescent bacteria toxicity tests.Results: The results showed that bioremediation could effectively degrade petroleum hydrocarbon (C10–C40) pollutants. After 42 days of remediation, the petroleum hydrocarbon (C10–C40) content of Group A (bioaugmented polluted wetland soil) decreased from 1.66 g/kg to 1.00 g/kg, and the degradation rate was 40.6%. The petroleum hydrocarbon (C10–C40) content of Group B (bioaugmented polluted farmland soil decreased from 4.00 g/kg to 1.94 g/kg, and the degradation rate was 51.6%. During the microbial remediation progress, the ecological toxicity of petroleum-contaminated soil first increased and then decreased. The photosynthetic pigment content index in the higher plant toxicity test, the earthworm survival index and the soil catalase activity all showed good agreement with the relative luminescence index of extracted DCM/DMSO in the luminescent bacterial toxicity test. The soil toxicity decreased significantly after remediation. Specifically, the photosynthetic pigment content of wheat were inhibited in the soil during the whole process (remediation for 42 days), and decreased to the minimum on remediation day 21. The 7-day and 14-day survival rate of earthworms in Group A and Group B gradually decreased in the soil remediation process, and then gradually increased, survival rate at the end of remediation was higher than at the beginning. Soil catalase activity was significantly negatively correlated with petroleum hydrocarbon (C10–C40) content (−0.988, −0.989). The ecological toxicity of contaminated soil reached to the maximum on the 21st day of remediation, relative luminosity of luminescent bacteria in dichloromethane/dimethyl sulfoxide extracts from Group A and Group B were 26.3% and 16.3%, respectively.Conclusion: Bioremediation could effectively degrade petroleum hydrocarbon (C10–C40) pollutants. Wheat photosynthetic pigment content, earthworm survival rate, soil catalase activity and relative luminescence of luminescent bacteria can better indicate the ecological toxicity of petroleum-contaminated soil in bioremediation process.

Luminescent bacteria are a fascinating component of marine microbial communities, often related to the light emissions in deep sea marine organisms. They are mainly affiliated with specific phylogenetic groups, such as Photobacterium, Vibrio, and Photorhabdus, and are sometimes involved in symbiotic relationships. However, the luminescence of some marine organisms remains a poorly understood process, and it is not always certain whether their luminescence is attributable to associated luminescent bacteria. In this study, for the first time, luminescent bacteria were isolated from two deep sea organisms, namely, the cephalopod Neorossia caroli and the teleost Chlorophthalmus agassizi. The isolation was carried out on glycerol-supplemented medium, and the search for the luxAB gene was performed on all isolates as a complementary tool to the culture-dependent techniques to detect bioluminescence by molecular approach. The optimum of salinity, temperature, and pH was evaluated by physiological tests for all isolates. The production of extracellular polymeric substances was also preliminarily screened. A total of 24 luminescent isolates were obtained, with an abundance from C. agassizi specimens. All the isolates were taxonomically characterized and were related to different species of Photobacterium, with the exception of Vibrio sp. CLD11 that was from C. agassizi. The luxAB gene was detected in about the 90% of the analysed strains.

Developments in industrial applications inevitably accelerate the discharge of enormous substances into the environment, whereas multi-component mixtures commonly cause joint toxicity which is distinct from the simple sum of independent effect. Thus, ecotoxicological assessment, by luminescent bioassays has recently brought increasing attention to overcome the environmental risks. Based on the above viewpoint, this review included a brief introduction to the occurrence and characteristics of toxic bioassay based on the luminescent bacteria. In order to assess the environmental risk of mixtures, a series of models for the prediction of the joint effect of multi-component mixtures have been summarized and discussed in-depth. Among them, Quantitative Structure-Activity Relationship (QSAR) method which was widely applied in silico has been described in detail. Furthermore, the reported potential mechanisms of joint toxicity on the luminescent bacteria were also overviewed, including the Trojan-horse type mechanism, funnel hypothesis, and fishing hypothesis. The future perspectives toward the development and application of toxicity assessment based on luminescent bacteria were proposed.

Vibrio fischeri bioluminescence inhibition has been widely used to test acute toxicities of metals and organics contaminants. However, the differences of metals and organics acute toxicities to V. fischeri have not been compared. Here, four heavy metals (Zn2+, Cu2+, Cd2+, Cr6+) and five organics (phenol, benzoic acid, p-hydroxy benzoic acid, nitro-benzene and benzene) acute toxicities to V. fischeri were investigated. Heavy metals toxicities to V. fischeri were increased along with the reaction time, while the organics toxicities kept the same level in different reaction times. In order to explain the difference, the relative cell death rate of V. fischeri was detected. In metals toxicities tests, the bioluminescence inhibition rate of V. fischeri was found to be significantly higher than the relative cell death rate (P

Bioluminescence, the phenomenon of light production by living organisms, occurs in forms of life as various as bacteria, fungi and animals. Nevertheless, light-emitting bacteria are the most abundant and widespread of luminescent organisms. Interestingly, most species of such bacteria live in marine environments. In this article, the biochemical mechanism of bacterial luminescence and its genetic regulation are summarized. Although the biochemistry and genetics of light emission by cells have been investigated in detail, the biological role of bacterial luminescence has remained obscure. Here, we discuss recent discoveries that shed new light on this problem. Finally, we provide examples of how bacterial luminescence can be employed in marine biotechnology, especially in the detection of toxic and mutagenic pollution in aquatic environments.