Abstract—Solving the problem of multidrug resistance currently requires the development of nonstandard approaches, since the potential for creating new antibiotics is almost exhausted. Controlling the metabolism of a pathogen in order to increase its susceptibility to antibacterial therapy is considered the most promising area of research for the creation of new combination drugs. In recent years, the number of studies devoted to investigation the role of the biosynthesis of the cell wall component ADP-heptose in the sensitivity of bacteria to antibiotics, as well as in the pathogenesis of bacterial infection, has increased. This review examines the main directions of scientific research in the field of use of ADP-heptose and its analogues in the treatment of bacterial infections. The exclusive role of ADP-heptose in the induction of an immune response is known through the activation of the NF-κB signaling pathway and the synthesis of pro-inflammatory cytokines. Our latest work has shown that disruption of the synthesis of ADP-heptose and the efflux of sedoheptulose-7-phosphate from the pentose phosphate pathway induces a redox imbalance and completely disorganizes the metabolism of low molecular weight thiols such as hydrogen sulfide, cysteine, and glutathione, which makes the bacterial cell extremely vulnerable to the action of antibiotics. We demonstrate that the hypersensitivity of ADP-heptose mutants to a wide range of antibiotics is explained by a new metabolic status rather than by changes in cell wall permeability. Thus, potential inhibitors of ADP-heptose biosynthesis can combine several positive qualities: an immunomodulatory effect and a powerful potentiating effect in combination with antibiotic therapy.

Abstract—Low molecular-weight thiols as glutathione and cysteine are an important part of the cell’s redox regulation system. Previously, we have shown that inactivation of ADP-heptose synthesis in Escherichia coli with a gmhA deletion induces the oxidative stress. It is accompanied by rearrangement of thiol homeostasis and increased sensitivity to antibiotics. In our study, we found that restriction of cysteine metabolism (∆cysB and ∆cysE) and inhibition of glutathione synthesis (∆gshAB) lead to a decrease in the sensitivity of the ∆gmhA mutant to antibiotics but not to its expected increase. At the same time, blocking of the export of cysteine (∆eamA) or increasing import (Ptet-tcyP) into cells of the oxidized form of cysteine–cystine leads to an even greater increase in the sensitivity of gmhA-deleted cells to antibiotics. In addition, there is no correlation between the cytotoxic effect of antibiotics and the level of reactive oxygen species (ROS), the total pool of thiols, or the viability of the initial cell population. However, a correlation between the sensitivity to antibiotics and the level of oxidized glutathione in cells was found in our study. Apparently, a decrease in the content of low-molecular-weight thiols saves NADPH equivalents and limits the processes of protein redox modification. This leads to increasing of resistance of the ∆gmhA strain to antibiotics. An increase in low-molecular-weight thiols levels requires a greater expenditure of cell resources, leads to an increase in oxidized glutathione and induces to greater increase in sensitivity of the ∆gmhA strain to antibiotics.

Counteraction of the origin and distribution of multidrug-resistant pathogens responsible for intra-hospital infections is a worldwide issue in medicine. In this brief review, we discuss the results of our recent investigations, which argue that many antibiotics, along with inactivation of their traditional biochemical targets, can induce oxidative stress (ROS production), thus resulting in increased bactericidal efficiency. As we previously showed, hydrogen sulfide, which is produced in the cells of different pathogens protects them not only against oxidative stress but also against bactericidal antibiotics. Next, we clarified the interplay of oxidative stress, cysteine metabolism, and hydrogen sulfide production. Finally, demonstrated that small molecules, which inhibit a bacterial enzyme involved in hydrogen sulfide production, potentiate bactericidal antibiotics including quinolones, beta-lactams, and aminoglycosides against bacterial pathogens in in vitro and in mouse models of infection. These inhibitors also suppress bacterial tolerance to antibiotics by disrupting the biofilm formation and substantially reducing the number of persister bacteria, which survive the antibiotic treatment. We hypothesise that agents which limit hydrogen sulfide biosynthesis are effective tools to counteract the origin and distribution of multidrug-resistant pathogens.

In cells of Escherichia coli, terminal oxidase bd-I encoded by the cydAB gene catalyzes the reduction of O2 to water using hydroquinone as an electron donor. In addition to the cydAB operon, two other genes, cydC and cydD, encoding the heterodimeric ATP-binding cassette-type transporter are essential for the assembly of cytochrome bd-I. It was shown that inactivation of cytochrome bd-I by the introduction of cydB or cydD deletions into the E. coli chromosome leads to supersensitivity of the bacteria to antibiotics of the quinolone and beta-lactam classes. The sensitivity of these mutants to antibiotics is partially suppressed by introduction of a constitutively expressed gene katG under the control of the Ptet promoter into their genome. The increased level of hydrogen sulfide resulting from the introduction of the mstA gene, encoding 3-mercaptopyruvate sulfurtransferase, under the control of the Ptet promoter, leads to the same effect. These data demonstrate the important role of cytochrome bd-I in the defense of bacteria from oxidative stress and bactericidal antibiotics.

The effect of E. colicyoA and cydA mutations that diminish the activity of bo' and bd-I terminal oxidases, respectively, on the lifespan of C. elegans nematodes was examined. It was demonstrated that the mean lifespan of the nematodes feeding on the cyoA and cydA mutants increased by 15.5 and 12.8%, respectively. It is known that cyoA and cydA mutants are characterized by the increased level of reactive oxygen species production. It is suggested that the lifespan extension in C. elegans is determined by moderate oxidative stress that occurs in the nematode organism upon culturing on these mutant bacteria.

The origin of bioluminescence in living organisms was first mentioned by Charles Darwin (1859) and remains obscure despite significant success achieved over the past decades. Here we discuss the mechanisms of bacterial bioluminescence. We have the main results from structural and functional analysis of the genes of lux operons, enzymes (luciferase), and mechanisms of bioluminescence in several species of marine bacteria, which belong to three genera, Vibrio, Aliivibrio, and Photobacterium (A. fischeri, V. harveyi, P. leiognathi, and P. phosphoreum), and in terrestrial bacteria of the genus Photorhabdus (Ph. luminescens). The structure and mechanisms for the regulation of the expression of the lux operons are discussed. The fundamental characteristics of luciferase and luciferase-catalyzed reactions (stages of FMNH2 and tetradecanal oxidation, dimensional structure, as well as folding and refolding of the macromolecule) are described. We also discuss the main concepts of the origin of bacterial bioluminescence and its role in the ecology of modern marine fauna, including its involvement in the processes of detoxification of the reactive oxygen species and DNA repair, as well as the bait hypothesis.

The paradoxical effect of deletion of the Escherichia coli genes cysK and cysM encoding cysteine synthase enzymes has been studied: such cysteine auxotrophs actively degrade the excess of cysteine transported from the medium to form H2S. We have shown that deletions of any of the known genes controlling the degradation of exogenous cysteine, including the genes aspC, mstA, cysK, cysM, tnaA, metC, and malY, as well as the newly discovered genes yciW, cyuA, cyuP, and cyuR, do not deprive the cysteine auxotrophs ΔcysK ΔcysM of the ability to degrade cysteine. Cysteine degradation in the ΔcysK ΔcysM mutant is positively regulated by the products of the cysB and cysE genes. It is significant that the ΔcysK ΔcysM mutant shows an increased transcription of the genes opposing the oxidative stress (sodA, catG, arcA, and cydD). We assume that oxidative stress in cells of the ΔcysK ΔcysM mutant is provoked by restriction of cysteine resynthesis, while cysB-dependent degradation of exogenous cysteine and generated H2S provide protection against oxidative stress.

The riboside derivative acadesine (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside) is currently being tested in clinical trials as a promising anti-tumor drug. Intracellular target of acadesine is adenosine monophosphate-activated protein kinase (АМРК), an important regulatory molecule of energy metabolism. It is expected that acadesine would be active in tumors under hypoxia conditions. In normoxia (cells incubated in 21 % oxygen), acadesine inhibited proliferation and induced cell death of breast adenocarcinoma, including the triple negative breast cancer line. When oxygen partial pressure was decreased to 1 % (experimental hypoxia), acadesine inhibited activation of reporter construct responsive to HIF-1α (hypoxia inducible factor 1 alpha) transcription factor. This effect was observed for acadesine in concentrations close to cytotoxic. Acadesine retained cytotoxicity under hypoxia and decreased the survival of the MDA-MB-231 cell line when used in combination with cisplatin. These results considerably widen acadesine’s field of application and allow to assume its efficacy in chemotherapy combination regimens for breast cancer, including the tumors with low oxygenation.

The feasibility of 1,3-butanediol biosynthesis through the inverted cycle of fatty acid β-oxidation in Escherichia coli cells was investigated by the rational metabolic engineering approach. CoA-dependent aldehyde dehydrogenase MhpF and alcohol dehydrogenases FucO and YqhD were used as terminal enzymes catalyzing conversion of 3-hydroxybutyryl-CoA to 1,3-butanediol. Constitutive expression of the corresponding genes in E. coli strains, which are deficient in mixed acid fermentation pathways and expressing fàd regulon genes under control of P trc-ideal-4 promoter, did not lead to the synthesis of 1,3-butanediol during anaerobic glucose utilization. Additional inactivation of fadE and ydiO genes, encoding acyl-CoA dehydrogenases, also did not cause synthesis of the target product. Constitutive expression of aceEF-lpdA operon genes encoding enzymes of pyruvate dehydrogenase complex led to an increase in anaerobic synthesis of ethanol. Synthesis of 1,3-butanediol was observed with the overexpression of acetyl-CoA C-acetyltransferase AtoB. Constitutive expression of atoB gene in a strain with a basal expression of alcohol/aldehyde dehydrogenase leads to synthesis of 0.3 mM of 1,3-butanediol.

Recently published data on the separation and quantification of natural nucleosides and some of their derivatives by thin-layer chromatography on silica gel have been summarized. The use of more than 20 mobile systems for the separation of more than 52 nucleosides and derivatives was discussed; in a few cases, the conditions for their densitometry quantitative analysis after TLC separation were considered. The works performed at GosNIIgenetika on the determination of inosine, thymidine, and acadesine with domestic Sorbfil plates were reviewed in detail.

We studied the cytotoxicity of acadesine (5-aminoimidazole-4-carboxamide-1--D-ribofuranoside) for tumor and normal cells of various species and tissue origin. In tumor cells, acadesine triggered non-apoptotic death; the potency of the compound to normal cells was substantially lower. Acadesine was toxic for tumor cells with multidrug resistant phenotypes caused by the transmembrane transporter Р-glycoprotein or lack of proapoptotic p53. Activity of adenosine receptors was required for acadesine-induced cell death, whereas functioning of АМР-dependent protein kinase was not required. A more pronounced cytotoxicity for tumor cells, as well as the non-canonical death mechanism(s), makes acadesine a promising candidate for antitumor therapy.

Bio-based succinate production from renewable resources has prospective economic and environmental benefits that caused heightened interest towards the study of succinate-producing microorganisms. The pathways of succinate formation have been well studied, and microorganisms that are capable of biomass convertion into the target substance (bacteria of the genera Actinobacillus, Anaerobiospirillum, and Mannheimia) have been isolated and characterized; however, the realization of economically feasible industrial processes using native producers still remains a challenge. Traditionally, the Escherichia coli bacterium has been used as a workhouse to develop new processes for the biosynthesis of many valuable chemicals due to the extensive knowledge of its metabolism, available genetic tools, and good growth characteristics, combined with low nutrient requirements. This review is focused on modern rational approaches to the construction of recombinant E. coli strains that efficiently produce succinic acid from glucose.

Electrogenicity of Shewanella oneidensis MR-1 mutants FRS1 and FRB1 with reducing activity 30–40% higher than in the original strain was studied in various microbial fuel cells (MFC) developed in the course of the work. The voltage and current density developed by the mutants were 1.7 times higher than in the case of S. oneidensis MR-1. A correlation was found between reducing activity of the cells and the voltage and current density developed in MFC. The possibility for enhanced bioelectricity production in MFC by genetic modification of S. oneidensis MR-1 was demonstrated.

Сконструирована экспрессионная плазмида и проведена гетерологичная экспрессия гена NAD+-зависимой формиатдегидрогеназы (ФДГ) из метилотрофной бактерии Moraxella sp. в клетках Shewanella oneidensis MR-1 в аэробных и анаэробных условиях. Активность рекомбинантной ФДГ была выявлена в клеточном лизате трансформантов при обоих условиях культивирования клеток. Интенсивность анаэробного дыхания, определенная по скорости конверсии акцептора электронов – фумарата, в сукцинат на среде с лактатом в качестве источника углерода у трансформанта с рекомбинантной ФДГ возрастала. При культивировании трансформанта S. oneidensis MR-1 с ФДГ в анаэробных условиях в микробном топливном элементе (МТЭ) обнаружено повышение уровня плотности тока.