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Several earthworm species are known to be able to withstand freezing. At the biochemical level, this ability is based on cryoprotectant accumulation as well as several other mechanisms. In this study, we used 1H NMR to investigate metabolomic changes in two freeze-tolerant earthworm taxa, Dendrobaena octaedra and one of the genetic lineages of Eisenia sp. aff. nordenskioldi f. pallida. A total of 45 metabolites were quantified. High concentrations of glucose were present in frozen tissues of both taxa. No other putative cryoprotectants were found. We detected high levels of glycolysis end products and succinate in frozen animals, indicating the activation of glycolysis. Concentrations of many other substances also significantly increased. On the whole, metabolic change in response to freezing was much more pronounced in the specimens of Eisenia sp. aff. nordenskioldi f. pallida, including signs of nucleotide degradation. [ABSTRACT FROM AUTHOR]

Simple Summary: Biological responses to rugged ecological factors causes changes in the metabolic pathways in aquatic organisms, which may manifest as changes in the tissue metabolomic composition. Therefore, establishing a correlation between the metabolite concentrations in aquatic animals and ecological factors is important for understanding the molecular mechanisms of biological responses to ecological stresses. In this work, we determined the concentrations of 57 major metabolites in the lenses of fish from three locations in Siberia (Russia) that differed in levels of dissolved oxygen (LDO) and water purity. We found that the increased due to CO2 emissions water acidity and the reduced LDO caused significant changes in the fish lenses' metabolomic compositions, including amino acids, organic acids, and energy metabolites. The obtained results can be used in monitoring the ecological state of water bodies. Multiple stressors related to changes in environmental conditions (such as water temperature, salinity, and natural and anthropogenic pollution) may cause biological responses of aquatic organisms that lead to significant variations in the biochemical reactions in their tissues and thereby change the concentrations of metabolites. We used a quantitative NMR-based metabolomic analysis of the fish lens for the evaluation of the influence of environmental factors on metabolic processes in aquatic animals. For this purpose, three species of freshwater fish—Perca fluviatilis, Rutilus rutilus lacustris, and Gymnocephalus cernua—were caught at approximately the same time at three locations in Siberia (Russia) that differed in levels of dissolved oxygen (LDO) and water purity, and the concentrations of 57 major metabolites in the fish lenses were determined. We found that the metabolomic profiles of the fish lenses strongly depended on the location. The obtained data demonstrated that two typical stressors for aquatic animals—a reduced LDO and anthropogenic water pollution—caused a largely similar metabolic response in the fish lenses that led to an increase in the concentrations of several amino acids and a decrease in sarcosine and phosphoethanolamine. At the same time, the composition of the major lens osmolytes depended mostly on the oxygen level, while variations in AMP (decrease) and NAD (increase) corresponded to the water pollution. We suggest that the eye lens is a very convenient tissue for studying the impact of ecological factors on the metabolic state of aquatic animals, fish in particular. [ABSTRACT FROM AUTHOR]

In this work, we for the first time report the identification of UV filters in the bird eye lens. We found that lenses of some raptors (black kite, common buzzard) and waterfowl (birds from Podicipedidae family) contain unusually high levels of reduced nicotinamide adenine dinucleotide (NADH)—a compound with high absorption in the UV-A range with a maximum at 340 nm. The lens metabolome of these birds also features an extremely low [NAD +]/[NADH] ratio. Chemometric analysis demonstrates that the differences between the metabolomic compositions of lenses with low and high NADH abundances should be attributed to the taxonomic features of bird species rather to the influence of the low [NAD +]/[NADH] ratio. We attributed this observation to the low metabolic activity in lens fiber cells, which make up the bulk of the lens tissue. Photochemical measurements show that properties of NADH as a UV filter are as good as that of UV filters in the human lens, including strong absorption in the UV-A spectral region, high photostability under both aerobic and anaerobic conditions, low yields of triplet state, fluorescence, and radicals under irradiation. Lenticular UV filters protect the retina and the lens from photo-induced damages and improve the visual acuity by reducing chromatic aberrations; therefore, the results obtained contribute to our understanding of the extremely high acuity of the raptor vision. [ABSTRACT FROM AUTHOR]

Simple Summary: Modern evolutionary biology offers a wide variety of methods to explore the evolution of species and to describe their relationships. The methods of DNA/RNA sequence analysis have been developing for decades and have become increasingly popular and reasonably reliable. Nevertheless, final phylogenetic trees for many taxa are still under debate because both classical and genomics-based approaches have their own limitations for phylogenetic tree reconstruction. Here, we propose the use of younger 'omics' methods, namely quantitative metabolomics, to aid the phylogeny reconstruction of vertebrates. We show that metabolomics-based hierarchical clustering analysis trees match, although not perfectly, to the genomics-based trees. In the current pilot study, we propose the use of quantitative metabolomics to reconstruct the phylogeny of vertebrates, namely birds. We determined the concentrations of the 67 most abundant metabolites in the eye lenses of the following 14 species from 6 orders of the class Aves (Birds): the Black kite (Milvus migrans), Eurasian magpie (Pica pica), Northern raven (Corvus corax), Eurasian coot (Fulica atra), Godlewski's bunting (Emberiza godlewskii), Great crested grebe (Podiceps cristatus), Great tit (Parus major), Hawfinch (Coccothraustes coccothraustes), Hooded crow (Corvus cornix), House sparrow (Passer domesticus), Rock dove (Columba livia), Rook (Corvus frugilegus), Short-eared owl (Asio flammeus) and Ural owl (Strix uralensis). Further analysis shows that the statistical approaches generally used in metabolomics can be applied for differentiation between species, and the most fruitful results were obtained with hierarchical clustering analysis (HCA). We observed the grouping of conspecific samples independently of the sampling place and date. The HCA tree structure supports the key role of genomics in the formation of the lens metabolome, but it also indicates the influence of the species lifestyle. A combination of genomics-based and metabolomics-based phylogeny could potentially resolve arising issues and yield a more reliable tree of life. [ABSTRACT FROM AUTHOR]

Introduction: Application of metabolomic methods to forensic studies may expand the limits of the post-mortem interval (PMI) estimation, and improve the accuracy of the estimation. To this end, it is important to determine which tissue is the most suitable for analysis, and which compounds are the most promising candidates for PMI estimation. Objectives: This work is aimed at the comparison of human serum, aqueous humor (AH), and vitreous humor (VH) as perspective tissues for metabolomic-based PMI estimation, at the determination of most promising PMI biomarkers, and at the development of method of PMI estimation based on the measurement of concentrations of PMI biomarkers. Methods: Quantitative metabolomic profiling of samples of the human serum, AH, and VH taken at different PMIs has been performed with the use of NMR spectroscopy. Results: It is found that the metabolomic changes in anatomically isolated ocular fluids are slower and smoother than that in blood. A good positive time correlation (Pearson coefficient r > 0.5) was observed for several metabolites, including hypoxanthine, choline, creatine, betaine, glutamate, and glycine. A model for PMI estimation based on concentrations of several metabolites in AH and VH is proposed. Conclusions: The obtained results demonstrate that the metabolomic analysis of AH and VH is more suitable for the PMI estimation than that of serum. The compounds with good positive time correlation can be considered as potential PMI biomarkers. [ABSTRACT FROM AUTHOR]

The absorption and fluorescence properties of the metabolomic (MET), water-soluble and urea-soluble protein fractions from the middle-age, aged, and cataractous human lenses have been measured. At 280 nm and 300 nm the major lens absorbers are crystallins, which absorb more than 90% of light in the UV-B region (280–315 nm). In middle-aged lenses, the absorption at 360 nm is mostly provided by UV filters contained in the MET fraction. With aging, and especially with the cataract development, the absorption of MET fraction in UV-A region (315–400 nm) decreases due to the drop of the UV filter concentration, while the absorption of protein fractions increases due to the accumulation of post-translational modifications. Consequently, the contribution of the MET fraction into the total lens absorption at 360 nm decays from 63% in middle-aged lenses to 25% in aged lenses to 3% in cataractous lenses. The fluorescence yield of the MET fraction from cataractous lenses also significantly increases. Therefore, the protection of the lens tissue against UV radiation in aged and cataractous lenses weakens: the absorption of UV-A light is mostly provided by modified crystallins and non-UV-filter metabolites, which are photochemically more active than the UV filters. The obtained data indicate that the aged and cataractous human lenses are more vulnerable to UV-A light than the middle-aged lenses. [ABSTRACT FROM AUTHOR]

Introduction: The analysis of post-mortem metabolomic changes in biological fluids opens the way to develop new methods for the estimation of post-mortem interval (PMI). It may also help in the analysis of disease-induced metabolomic changes in human tissues when the postoperational samples are compared to the post-mortem samples from healthy donors. Objectives: The goals of this study are to observe and classify the post-mortem changes occurring in the rabbit blood, aqueous and vitreous humors (AH and VH), to identify the potential PMI markers among a wide range of metabolites, and also to determine which biological fluid-blood, AH or VH-is more suitable for the PMI estimation. Methods: The quantitative metabolomic profiling of samples of the rabbit serum, AH and VH taken at different PMIs has been performed with the combined use of high-frequency NMR and high-resolution LC-MS methods. Results: The quantitative levels of 61 metabolites in the rabbit serum, AH and VH at different PMIs have been measured. It has been found that the post-mortem metabolomic changes in AH and VH proceed slower than in blood, and the data scattering is lower. Among the metabolites whose concentrations increase with time, the most significant and linear growth is found for hypoxanthine, choline and glycerol. Conclusion: The obtained results suggest that the ocular fluids AH and VH may have some advantages over blood serum for the search of potential biochemical markers for the PMI estimation. Among the compounds studied in the present work, hypoxanthine, choline and glycerol give the biggest promise as the potential PMI biomarkers. [ABSTRACT FROM AUTHOR]

The photophysics and photochemistry of kynurenic acid (KNA) and kynurenine yellow (KNY) in neutral aqueous solutions were investigated using time-resolved optical spectroscopy. Both molecules have similar quinoline-like structures, the only difference being the absence of conjugation in the nitrogen containing cycle in KNY. The main channel of S1 excited state decay in the case of partially-unconjugated KNY is the solvent assisted S1→ S0 radiationless transition via intermolecular hydrogen bonds (ΦIC = 0.96), whereas, in the case of fully-conjugated KNA, it is intersystem crossing to the triplet state (ΦT = 0.82). The major intermediate products of the singlet excited KNY deactivation are the triplet state (ΦT = 0.022) and, most probably, the enol form (Φenol = 0.012), which decay with the formation of 2,3-dihydro-4-hydroxyquinoline and 4-hydroxyquinoline, respectively. The results obtained show that KNA and KNY, which are products of the decomposition of the UV filter kynurenine, are significantly more photoactive and less photostable than the parent molecule. [ABSTRACT FROM AUTHOR]

Quantitative metabolomic analysis was performed for eleven tissues of freshwater fish pike-perch (Sander lucioperca), including gill, heart, liver, kidney, spleen, muscle, brain, milt, lens, aqueous (AH) and vitreous (VH) humors with the use of NMR spectroscopy. The absolute values of concentrations were determined for more than 65 most abundant metabolites in every tissue. It was found that from the metabolomic viewpoint, kidney and gill are the most similar tissues, while the metabolomic compositions of ocular tissues—lens, AH, and VH significantly differ from that of other tissues. The combinations of intracellular osmolytes and antioxidants are specific for every tissue. In particular, the concentration of antioxidant ovothiol A in the lens is much higher than in any other tissue, while the brain enjoys the elevated level of ascorbate. The most abundant osmolyte in the fish spleen, muscle, and heart is taurine, and in the brain, gill, and lens—myo-inositol. Other important osmolytes specific for particular tissues are N-acetyl-histidine, N-acetyl-aspartate, betaine, threonine-phosphoethanolamine, and serine-phosphoethanolamine. The quantitative data obtained in the present work can be used as the baseline metabolite concentrations in the fish tissues to evaluate the influence of seasonal, ecological and other factors on the fish metabolism. [ABSTRACT FROM AUTHOR]

Three small molecules consisting of thieno‐fused naphthalimide units connected via aromatic linkers were synthesized to study the effect of fused thiophene rings on the properties of naphthalimide‐based molecules. A protocol for the synthesis of thienonaphthalimide‐based molecules without prior preparation and use of thienonaphthalimide precursors and organoelement compounds (organolithium, organotin, or organoboron compounds) was developed. The protocol is based on double thienannulation of bis‐alkyne substrates with sodium sulfide. The thin‐film morphology, photophysical and electrochemical properties of the obtained small molecules were studied. Single‐layer non‐doped organic light‐emitting diodes based on fluorene‐bridged thienonaphthalimide dimer showed yellow emission with luminance of 2200 cd/m2, and current efficiency of 0.35 cd/A. Combination of transient electroluminescence and photo‐CELIV methods allowed to estimate electron and hole mobility in the synthesized compounds; both are in order of 10−6 cm2V−1 s−1. [ABSTRACT FROM AUTHOR]

Simple Summary: The lack of oxygen is a significant challenge for most animals, which can lead to tissue damage and death. The Siberian frog Rana amurensis is so far the only known amphibian capable of surviving water anoxia for a long time. We compared metabolomic profiles of the liver, brain, and heart under hypoxia for the Siberian frog and the Far Eastern (Rana dybowskii) frog, which is highly susceptible to the lack of oxygen. One of the most interesting findings was that the organs of the Far Eastern frog had more lactate (glycolysis end product) than those of the Siberian frog despite a much shorter exposure time. The amounts of succinate were similar between the two species. Interestingly, glycerol and 2,3-butanediol were found to be abundant under hypoxia in the Siberian frog, but not in the Far Eastern frog. The role of these substances are still unclear. Based on the obtained data, we suggest a bioenergetic pathway for metabolic changes in the Siberian frog under anoxia. Anoxia is a significant challenge for most animals, as it can lead to tissue damage and death. Among amphibians, the Siberian frog Rana amurensis is the only known species capable of surviving near-zero levels of oxygen in water for a prolonged period. In this study, we aimed to compare metabolomic profiles of the liver, brain, and heart of the Siberian frog exposed to long-term oxygen deprivation (approximately 0.2 mg/L water) with those of the susceptible Far Eastern frog (Rana dybowskii) subjected to short-term hypoxia to the limits of its tolerance. One of the most pronounced features was that the organs of the Far Eastern frog contained more lactate than those of the Siberian frog despite a much shorter exposure time. The amounts of succinate were similar between the two species. Interestingly, glycerol and 2,3-butanediol were found to be significantly accumulated under hypoxia in the Siberian frog, but not in the Far Eastern frog. The role and biosynthesis of these substances are still unclear, but they are most likely formed in certain side pathways of glycolysis. Based on the obtained data, we suggest a pathway for metabolic changes in the Siberian frog under anoxia. [ABSTRACT FROM AUTHOR]

Metabolomic profiles of somatic cells, embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs) reflect their metabolic phenotypes. The comparative study of metabolomes of these cells is important for understanding the differences in metabolism between somatic and pluripotent cells, and also the possible differences between ESCs and iPSCs. Here, we performed for the first time the metabolomic analysis of rat ESCs, iPSCs, and embryonic fibroblasts (EFs) at both quantitative and semi-quantitative levels using NMR spectroscopy and liquid chromatography with mass spectrometric detection, respectively. The total of 106 metabolites has been identified, and the concentrations of 51 compounds have been measured. It is found that the reprogramming of rat EFs into iPSCs affects virtually all metabolic pathways and causes drastic changes in the cell metabolomic profile. The difference between ESCs and iPSCs is much less pronounced: the concentrations of the majority of metabolites in ESCs and iPSCs are similar, and significant differences were observed for only several compounds, including adenosine, cysteic acid, glycerophosphoglycerol, inositol phosphate, glucose, myo-inositol, phosphoserine, xanthosine, guanosine. The observed differences between the metabolomic compositions of ESCs and iPSCs do not influence the pluripotent ability of iPSCs. [ABSTRACT FROM AUTHOR]

Simple Summary: The moor frog Rana arvalis can tolerate freezing to low temperatures, up to −16 °C. We performed metabolomic analysis of the liver and hindlimb muscles of frozen and control R. arvalis. We found that the moor frog synthesizes glucose and glycerol in similar concentrations as low molecular weight cryoprotectants. This is the first such case reported for the genus Rana, which was believed to use glucose only. We found that freezing upregulates glycolysis, with the accumulation of several end products: lactate, alanine, ethanol, and, possibly, 2,3-butanediol. To our knowledge, this is also the first report of ethanol as an end product of glycolysis in terrestrial vertebrates. We observed highly increased concentrations of nucleotide degradation products, implying high level of stress. We found almost no signs of adaptations to reoxygenation stress, with overall low levels of antioxidants. We also performed metabolomics analysis of subcutaneous ice that was found to contain glucose, glycerol, and several other substances. The moor frog Rana arvalis is one of a few amphibians that can tolerate freezing to low temperatures, up to −16 °C. In this study, we performed metabolomic analysis of the liver and hindlimb muscles of frozen and control R. arvalis. We found that the moor frog synthesizes glucose and glycerol in similar concentrations as low molecular weight cryoprotectants. This is the first such case reported for the genus Rana, which was believed to use glucose only. We found that freezing upregulates glycolysis, with the accumulation of several end products: lactate, alanine, ethanol, and, possibly, 2,3-butanediol. To our knowledge, this is also the first report of ethanol as an end product of glycolysis in terrestrial vertebrates. We observed highly increased concentrations of nucleotide degradation products, implying high level of stress. The Krebs cycle arrest resulted in high concentrations of succinate, which is common for animals. However, we found almost no signs of adaptations to reoxygenation stress, with overall low levels of antioxidants. We also performed metabolomics analysis of subcutaneous ice that was found to contain glucose, glycerol, and several other substances. [ABSTRACT FROM AUTHOR]

(1) Recently, metabolic profiling of the tissue in the native state or extracts of its metabolites has become increasingly important in the field of metabolomics. An important factor, in this case, is the presence of blood in a tissue sample, which can potentially lead to a change in the concentration of tissue metabolites and, as a result, distortion of experimental data and their interpretation. (2) In this paper, the metabolomic profiling based on NMR spectroscopy was performed to determine the effect of blood contained in the studied samples of brain tissue on their metabolomic profile. We used 13 male laboratory CD-1® IGS mice for this study. The animals were divided into two groups. The first group of animals (n = 7) was subjected to the perfusion procedure, and the second group of animals (n = 6) was not perfused. The brain tissues of the animals were homogenized, and the metabolite fraction was extracted with a water/methanol/chloroform solution. Samples were studied by high-frequency 1H-NMR spectroscopy with subsequent statistical data analysis. The group comparison was performed with the use of the Student's test. We identified 36 metabolites in the brain tissue with the use of NMR spectroscopy. (3) For the major set of studied metabolites, no significant differences were found in the brain tissue metabolite concentrations in the native state and after the blood removal procedure. (4) Thus, it was shown that the presence of blood does not have a significant effect on the metabolomic profile of the brain in animals without pathologies. [ABSTRACT FROM AUTHOR]

Two acceptor small molecules consisting of 2‐(11‐oxoanthra[2,1‐b]thiophen‐6‐ylidene)dipropanedinitrile frameworks connected by a bis(thiophen‐2‐ylethynyl)arene bridge were synthesized by the two‐step sequence of Sonogashira cross‐coupling and Knoevenagel condensation in order to investigate their performance as non‐fullerene acceptors in organic solar cells. Optical, electrochemical and photovoltaic properties of new 2,2′‐[2,2′‐(5,5′‐(arenediyl)bis(ethyne‐2,1‐diyl)bis(thien‐5,2‐diyl))bis(11‐oxoanthra[2,1‐b]thiophen‐6‐ylidene)]dipropanedinitriles and previously studied analogs of 2,2′‐[2,2′‐arenediylbis(11‐oxoanthra[1,2‐b]thiophene‐6‐ylidene)]dipropanedinitriles were compared to assess the effect of introducing ethynylthiophene units between the arene linker and the 2‐(11‐oxoanthrathiophen‐6‐ylidene)propanedinitrile units. Despite the proper energy level alignment and morphology, composites of the newly synthesized compounds with the PBDB‐T donor polymer demonstrate a moderate PCE of 0.54 %. The small value of the short circuit current as compared to composites with fullerene acceptors is probably due to the low electron mobility in the newly synthesized compounds. The low electron mobility, in turn, is probably cause by the LUMO localization at the edge units of the acceptor‐type molecules, in contrast to the almost uniform LUMO delocalization over the whole π‐conjugated system for high‐performing non‐fullerene acceptors such as ITIC. [ABSTRACT FROM AUTHOR]

Simple Summary: The Siberian salamander is a unique amphibian that is capable to survive long-term freezing at −55 °C. We used 1H-NMR analysis to study quantitative changes of multiple metabolites in liver and hindlimb muscle of the Siberian salamander in response to freezing. For the majority of molecules we observed significant changes in concentrations. Glycerol content in frozen organs was as high as 2% w/w, which confirms its role as a cryoprotectant. No other putative cryoprotectants were detected. Freezing resulted in increased concentrations of glycolysis products: lactate and alanine. Unexpectedly, we detected no increase in concentrations of succinate, which accumulates under ischemia in various tetrapods. Freezing proved to be a dramatic stress with high levels of nucleotide degradation products. There was also significant increase in the concentrations of choline and glycerophosphocholine, which may be interpreted as the degradation of biomembranes. Thus, we found that freezing results not only in macroscopical damage due to ice formation, but also to degradation of DNA and biomembranes. The Siberian salamander Salamandrella keyserlingii Dybowski, 1870 is a unique amphibian that is capable to survive long-term freezing at −55 °C. Nothing is known on the biochemical basis of this remarkable freezing tolerance, except for the fact that it uses glycerol as a low molecular weight cryoprotectant. We used 1H-NMR analysis to study quantitative changes of multiple metabolites in liver and hindlimb muscle of S. keyserlingii in response to freezing. For the majority of molecules we observed significant changes in concentrations. Glycerol content in frozen organs was as high as 2% w/w, which confirms its role as a cryoprotectant. No other putative cryoprotectants were detected. Freezing resulted in ischemia manifested as increased concentrations of glycolysis products: lactate and alanine. Unexpectedly, we detected no increase in concentrations of succinate, which accumulates under ischemia in various tetrapods. Freezing proved to be a dramatic stress with reduced adenosine phosphate pool and high levels of nucleotide degradation products (hypoxanthine, β-alanine, and β-aminoisobutyrate). There was also significant increase in the concentrations of choline and glycerophosphocholine, which may be interpreted as the degradation of biomembranes. Thus, we found that freezing results not only in macroscopical damage due to ice formation, but also to degradation of DNA and biomembranes. [ABSTRACT FROM AUTHOR]

Bacteriophages are promising antibacterial agents. Although they have been recognized as bacterial viruses and are considered to be non-interacting with eukaryotic cells, there is growing evidence that phages may have a significant impact on the immune system via interactions with macrophages, neutrophils, and T-cell polarization. In this study, the influence of phages of podovirus, siphovirus, and myovirus morphotypes on humoral immunity of CD-1 mice was investigated. In addition, tissue distribution of the phages was tested in these mice. No common patterns were found either in the distribution of phages in mice or in changes in the levels of cytokines in the sera of mice once injected with phages. Importantly, pre-existing IgM-class antibodies directed against capsid proteins of phages with myovirus and siphovirus morphotypes were identified in mice before immunization. After triple immunization of CD1-mice with phages without any adjuvant, levels of anti-phage serum polyclonal IgG antibodies increased. Immunogenic phage proteins recognized by IgM and/or IgG antibodies were identified using Western blot analysis and mass spectrometry. In addition, mice serum collected after immunization demonstrated neutralizing properties, leading to a substantial decrease in infectivity of investigated phages with myovirus and siphovirus morphotypes. Moreover, serum samples collected before administration of these phages exhibited some ability to reduce the phage infectivity. Furthermore, Proteus phage PM16 with podovirus morphotype did not elicit IgM or IgG antibodies in immunized mice, and no neutralizing activities against PM16 were revealed in mouse serum samples before and after immunization. [ABSTRACT FROM AUTHOR]

The Siberian wood frog Rana amurensis is a recently discovered example of extreme hypoxia tolerance that is able to survive several months without oxygen. We studied metabolomic profiles of heart and liver of R. amurensis exposed to 17 days of extreme hypoxia. Without oxygen, the studied tissues experience considerable stress with a drastic decrease of ATP, phosphocreatine, and NAD+ concentrations, and concomitant increase of AMP, creatine, and NADH. Heart and liver switch to different pathways of glycolysis with differential accumulation of lactate, alanine, succinate, as well as 2,3-butanediol (previously not reported for vertebrates as an end product of glycolysis) and depletion of aspartate. We also observed statistically significant changes in concentrations of certain osmolytes and choline-related compounds. Low succinate/fumarate ratio and high glutathione levels indicate adaptations to reoxygenation stress. Our data suggest that maintenance of the ATP/ADP pool is not required for survival of R. amurensis, in contrast to anoxia-tolerant turtles. [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae is a common pathogen, associated with a wide spectrum of infections, and clinical isolates of K. pneumoniae often possess multiple antibiotic resistances. Here, we describe a novel lytic N4-like bacteriophage KP8, specific to K. pneumoniae, including its genome, partial structural proteome, biological properties, and proposed taxonomy. Electron microscopy revealed that KP8 belongs to the Podoviridae family. The size of the KP8 genome was 73,679 bp, and it comprised 97 putative open reading frames. Comparative genome analysis revealed that the KP8 genome possessed the highest similarity to the genomes of Enquatrovirus and Gamaleyavirus phages, which are N4-like podoviruses. In addition, the KP8 genome showed gene synteny typical of the N4-like podoviruses and contained the gene encoding a large virion-encapsulated RNA polymerase. Phylogenetic analysis of the KP8 genome revealed that the KP8 genome formed a distinct branch within the clade, which included the members of Enquatrovirus and Gamaleyavirus genera besides KP8. The average evolutionary divergences KP8/Enquatrovirus and KP8/Gamaleyavirus were 0.466 and 0.447 substitutions per site (substitutes/site), respectively, similar to that between Enquatrovirus and Gamaleyavirus genera (0.468 substitutes/site). The obtained data suggested that Klebsiella phage KP8 differs from other similar phages and may represent a new genus within the N4-like phages. [ABSTRACT FROM AUTHOR]