Interaction of Antibiotics and Humic Substances: Environmental Consequences and Remediation Prospects

The occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystems. Humic substances (HS) influence the mobility, reactivity, and bioavailability of antibiotics in the environment significantly due to their interaction. As a result, HS can affect the dissemination of antibiotic-resistance genes, which is one of the main problems arising from contamination with antibiotics. The review provides quantitative data on the binding of HS with fluoroquinolones, macrolides, sulfonamides, and tetracyclines and reports the proposed mechanisms of their interaction. The main issues of the quantification of antibiotic-HS interaction are discussed, which are a development of standard approaches and the accumulation of a dataset using a standard methodology. This would allow the implementation of a meta-analysis of data to reveal the patterns of the binding of antibiotics to HS. Examples of successful development of humic-based sorbents for fluoroquinolone and tetracycline removal from environmental water systems or polluted wastewaters were given. Data on the various effects of HS on the dissemination of antibiotic-resistance genes (ARGs) were summarized. The detailed characterization of HS properties as a key point of assessing the environmental consequences of the formation of antibiotic-HS complexes, such as the dissemination of antibiotic resistance, was proposed.

A Systematic Study of the Antioxidant Capacity of Humic Substances against Peroxyl Radicals: Relation to Structure

Humic substances (HS) are natural supramolecular systems of high- and low-molecular-weight compounds with distinct immunomodulatory and protective properties. The key beneficial biological activity of HS is their antioxidant activity. However, systematic studies of the antioxidant activity of HS against biologically relevant peroxyl radicals are still scarce. The main objective of this work was to estimate the antioxidant capacity (AOC) of a broad set of HS widely differing in structure using an oxygen radical absorption capacity (ORAC) assay. For this purpose, 25 samples of soil, peat, coal, and aquatic HS and humic-like substances were characterized using elemental analysis and quantitative ¹³C solution-state NMR. The Folin–Ciocalteu method was used to quantify total phenol (TP) content in HS. The determined AOC values varied in the range of 0.31–2.56 μmol Trolox eqv. mg⁻¹, which is close to the values for ascorbic acid and vitamin E. Forward stepwise regression was used to reveal the four main factors contributing to the AOC value of HS: atomic C/N ratio, content of O-substituted methine and methoxyl groups, and TP. The results obtained clearly demonstrate the dependence of the AOC of HS on both phenolic and non-phenolic moieties in their structure, including carbohydrate fragments.

Relation between lignin molecular profile and fungal exo-proteome during kraft lignin modification by Trametes hirsuta LE-BIN 072

The process of kraft lignin modification by the white-rot fungus Trametes hirsuta was investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS), and groups of systematically changing compounds were delineated. In the course of cultivation, fungus tended to degrade progressively more reduced compounds and produced more oxidized ones. However, this process was not gradual - the substantial discontinuity was observed between 6th and 10th days of cultivation. Simultaneously, the secretion of ligninolytic peroxidases by the fungus was changing in a cascade manner - new isoenzymes were added to the mixture of the already secreted ones, and once new isoenzyme appeared both its relative quantity and number of isoforms increased as cultivation proceeded. It was proposed, that the later secreted peroxidases (MnP7 and MnP1) possess higher substrate affinity for some phenolic compounds and act in more specialized manner than the early secreted ones (MnP5 and VP2).

Interactions between Humic Substances and Microorganisms and Their Implications for Nature-like Bioremediation Technologies

The state of the art of the reported data on interactions between microorganisms and HSs is presented herein. The properties of HSs are discussed in terms of microbial utilization, degradation, and transformation. The data on biologically active individual compounds found in HSs are summarized. Bacteria of the phylum Proteobacteria and fungi of the phyla Basidiomycota and Ascomycota were found to be the main HS degraders, while Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were found to be the predominant phyla in humic-reducing microorganisms (HRMs). Some promising aspects of interactions between microorganisms and HSs are discussed as a feasible basis for nature-like biotechnologies, including the production of enzymes capable of catalyzing the oxidative binding of organic pollutants to HSs, while electron shuttling through the utilization of HSs by HRMs as electron shuttles may be used for the enhancement of organic pollutant biodegradation or lowering bioavailability of some metals. Utilization of HSs by HRMs as terminal electron acceptors may suppress electron transfer to CO2, reducing the formation of CH4 in temporarily anoxic systems. The data reported so far are mostly related to the use of HSs as redox compounds. HSs are capable of altering the composition of the microbial community, and there are environmental conditions that determine the efficiency of HSs. To facilitate the development of HS-based technologies, complex studies addressing these factors are in demand.

Optical Properties of Soil Dissolved Organic Matter Are Related to Acidic Functions of Its Components as Revealed by Fractionation, Selective Deuteromethylation, and Ultrahigh Resolution Mass Spectrometry

The goal of this study was to establish a relationship between the optical properties of soil dissolved organic matter (DOM) and acidic functions carried out by its individual constituents. We obtained 12 fractions of DOM samples using sequential solid phase extraction on nonionic sorbent at steadily lowered pH values: 7, 5, 3, 2, which correspond to low bounds of pK_a values of phenols, aliphatic, and aromatic carboxylic acids, and ketoacids. The structural studies were conducted with the use of NMR and selective deuteromethylation of isolated fractions coupled to ultrahigh resolution mass spectrometry. First, a gradual shift of molecular compositions was observed from reduced components to aromatic oxidized compounds isolated at pH 7 and 2, respectively. Changes in molecular compositions were accompanied by a red shift of fluorescence spectra. Further application of deuteromethylation enabled us to distinguish DOM constituents with different amounts of carboxylic groups. Moreover, identification of structural isomers in a single DOM sample was achieved. Statistical analysis revealed that red shift of fluorescence is facilitated by the increase of a contribution of aromatic poly(carboxylic acid)s with high conjugation lengths. Additionally, analysis of the labeled fractionated permafrost thaw DOM directly showed carboxyl-rich alicyclic molecules, while the same components from lower-latitude DOM were assigned to lignin-like species.

Behavior of humic substances in the liquid-liquid system directly measured using tritium label

Humic substances (HS) in the aqueous solutions can be considered as colloidal particles formed by amphiphilic units. HS form micelles-like structures at concentrations close to 5 g/L. However colloidal behavior of HS at concentrations below 100 mg/L is unknown. Using radiotracer assay we have shown that in this concentration range HS form rare adsorption layers at the liquid/liquid interface and penetrate into the organic phase with the distribution ratio close to 10^-3. We found that pH and HS molecular weight strongly influence on the distribution ratio but do not significantly change the adsorption. Furthermore, colloidal properties of HS are strongly depending on its origin: the highest surface activity was shown for HS separated from peat and the least was observed for HS separated from soils. We anticipate our assay to be a helpful tool for detailed analysis and modeling HS and humic-like materials colloidal behavior in the environment.

The Structural Arrangement and Relative Abundance of Aliphatic Units May Effect Long-Wave Absorbance of Natural Organic Matter as Revealed by 1H NMR Spectroscopy

The objective of this study was to shed light on structural features which underlay intensity of long wave absorbance of natural organic matter (NOM) using ¹H NMR spectroscopy. For this purpose, a set of the NOM samples was assembled from arctic and nonarctic sampling sites (the Kolyma river basin and Moscow region, respectively). It was to ensure a substantial difference in the humification degree of the isolated organic matter-the biogeochemical proxy of the long-wave absorbance of NOM. The assembled NOM set was analyzed using solution-state ¹H NMR spectroscopy. The distribution of both backbone and exchangeable protons was determined using acquisition of spectra in three different solvents. The substantially higher contribution of nonfunctionalized aliphatic moieties CHn (e.g., materials derived from linear terpenoids, MDLT) in the arctic NOM samples was revealed as compared to the nonarctic ones. The latter were characterized with the higher content of CHα protons adjacent to electron-withdrawing groups which belong to carboxyl rich alicyclic moieties (CRAMs) or to aromatic constituents of NOM. We have calculated a ratio of CHn to CHα protons as a structural descriptor which showed significant inverse correlation to intensity of long wave absorbance assessed with a use of E₄/ E₆ ratio and the slope of absorption spectrum. The steric hindrance of aromatic chromophoric groups of the NOM ensemble by bulky nonfunctionalized aliphatic moieties (e.g., MDLT) was set as a hypothesis for explanation of this phenomenon. The bulky aliphatics might increase a distance between the interacting groups resulting in inhibition of electronic (e.g., charge-transfer) interactions in the NOM ensemble. The obtained relationships were further explored using Fourier transform mass spectrometry as complementary technique to ¹H NMR spectroscopy. The data obtained on correlation of molecular composition of NOM with ¹H NMR data and optical properties were very supportive of our hypothesis that capabilities of NOM ensemble of charge transfer interactions can be dependent on structural arrangement and relative abundance of nonabsorbing aliphatic moieties.

Key Roles of Size and Crystallinity of Nanosized Iron Hydr(oxides) Stabilized by Humic Substances in Iron Bioavailability to Plants

Availability of Fe in soil to plants is closely related to the presence of humic substances (HS). Still, the systematic data on applicability of iron-based nanomaterials stabilized with HS as a source for plant nutrition are missing. The goal of our study was to establish a connection between properties of iron-based materials stabilized by HS and their bioavailability to plants. We have prepared two samples of leonardite HS-stabilized iron-based materials with substantially different properties using the reported protocols and studied their physical chemical state in relation to iron uptake and other biological effects. We used Mössbauer spectroscopy, XRD, SAXS, and TEM to conclude on iron speciation, size, and crystallinity. One material (Fe-HA) consisted of polynuclear iron(III) (hydr)oxide complexes, so-called ferric polymers, distributed in HS matrix. These complexes are composed of predominantly amorphous small-size components (<5 nm) with inclusions of larger crystalline particles (the mean size of (11 ± 4) nm). The other material was composed of well-crystalline feroxyhyte (δ'-FeOOH) NPs with mean transverse sizes of (35 ± 20) nm stabilized by small amounts of HS. Bioavailability studies were conducted on wheat plants under conditions of iron deficiency. The uptake studies have shown that small and amorphous ferric polymers were readily translocated into the leaves on the level of Fe-EDTA, whereas relatively large and crystalline feroxyhyte NPs were mostly sorbed on the roots. The obtained data are consistent with the size exclusion limits of cell wall pores (5-20 nm). Both samples demonstrated distinct beneficial effects with respect to photosynthetic activity and lipid biosynthesis. The obtained results might be of use for production of iron-based nanomaterials stabilized by HS with the tailored iron availability to plants. They can be applied as the only source for iron nutrition as well as in combination with the other elements, for example, for industrial production of "nanofortified" macrofertilizers (NPK).

[THE SPECIFITY OF MOTOR SYSTEMS ORGANISATION AND IT''S INFLUENCES ON RESULTNESS OF ACTIVITY IN HEALTHY PEOPLE AND PATIENTS WITH EPILEPSY]

The specificity of motor systems and its influences on effectiveness of modeling purposeful activity in 46 healthy people and 110 patients with epilepsy was studied. Using cluster analysis the patients with epilepsy were divided in 2 groups: high- and low efficient. The differences of physiological parameters, which characterize the activity of central level of motor systems and visual-motor reaction, were determined. The high level of activation of cortical mechanisms of decision-making and preparedness to motor reaction in the group of healthy people and low effectiveness associated with insufficient activation of these mechanisms in the group of patients with epilepsy was described.

Label Distribution in Tissues of Wheat Seedlings Cultivated with Tritium-Labeled Leonardite Humic Acid

Humic substances (HS) play important roles in the biotic-abiotic interactions of the root plant and soil contributing to plant adaptation to external environments. However, their mode of action on plants remains largely unknown. In this study the HS distribution in tissues of wheat seedlings was examined using tritium-labeled humic acid (HA) derived from leonardite (a variety of lignites) and microautoradiography (MAR). Preferential accumulation of labeled products from tritiated HA was found in the roots as compared to the shoots, and endodermis was shown to be the major control point for radial transport of label into vascular system of plant. Tritium was also found in the stele and xylem tissues indicating that labeled products from tritiated HA could be transported to shoot tissues via the transpiration stream. Treatment with HA lead to an increase in the content of polar lipids of photosynthetic membranes. The observed accumulation of labeled HA products in root endodermis and positive impact on lipid synthesis are consistent with prior reported observations on physiological effects of HS on plants such as enhanced growth and development of lateral roots and improvement/repairs of the photosynthetic status of plants under stress conditions.

[Transformation of humic substances of highly oxidized brown coal by the basidiomycetes fungi Trametes hirsuta and Trametes maxima]

The ability of the white rot basidiomycetes Trametes hirsuta and Trametes maxima to transform coal humic substances (HS's) under the conditions of solid phase cultivation in the presence or absence of an easily available source of corbon (glucose) has been studied. It was shown that during the growth of the fungal strains used in media, containing HS's, destructive and condensation processes of HS transformation proceeded simultaneously. Based on a comparative physicochemical analysis of the initial HS's and HS's transformed by the fungi, it was established that, despite the introduction of glucose may favor a deeper transformation of HS's by basidiomycetes, the general direction of their modification is dominant reduction or oxidation and is determined by the physiological biochemical peculiarities of the strain used.

[Effect of Coriolus hirsutus laccase on atrazine adsorption and desorption by different types of soil ]

Study of adsorption-desorption behavior of herbicide atrazine in soils of different geographical zones in the presence of Coriolus hirsutus laccase was performed. Laccase was shown to significantly increase adsorption coefficient and to facilitate irreversible adsorption of atrazine to soil. Supposably, laccase catalyzes oxidative binding of atrazine to soil.

[A comparative characterization of fungal melanin and the humin-like substances synthesized by Cerrena maxima 0275]

Comparative studies of fungal melanin and two preparations of the high-molecular-weight humin-like substances formed during a solid-phase cultivation of the basidiomycete Cerrena maxima 0275 for 45 and 70 days were performed. The fungal melanin from Aspergillus niger and the humin-like substances synthesized by the basidiomycete C. maxima 0275 are similar in their physicochemical properties (elemental composition and behavior in acids and alkalis) and auxin-like activities. However, these biopolymers differ, essentially, at the structural level. According to IR spectroscopy data, the obtained humin-like substances display a higher similarity to natural humic acids and are more diverse in their functional groups compared with fungal melanins. Presumably, this is connected with the fact that laccase is involved in formation of humin-like substances; moreover, this enzyme is involved not only in the synthesis of these polymers, but also in their modification and degradation.

Molecular weight characteristics of humic substances from different environments as determined by size exclusion chromatography and their statistical evaluation

Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1)to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition: humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7-30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5-4.4) were seen for peat HF and soil HA, while much lower values (1.6-3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds.

Binding of atrazine to humic substances from soil, peat and coal related to their structure

Partition coefficients for the binding affinities of atrazine to 16 different humic materials were determined by the ultrafiltration HPLC technique. Sources included humic acids (HA), fulvic acids (FA), and combined humic and fulvic fractions (HF) from soil, peat, and coal humic acid. Each of the humic materials was characterized by elemental composition, molecular weight, and composition of main structural fragments determined by 13C solution-state NMR. The magnitude of K(OC) values varied from 87 to 575 L/kg of C, demonstrating relatively low binding affinity of humic substances (HS) for atrazine. On the basis of the measured K(OC) values, the humic materials can be arranged in the following order: coal HA approximately = gray wooded soil HA > chernozemic soil HA and HF > sod-podzolic soil HA approximately = peat HF > sod-podzolic soil FA >> peat dissolved organic matter. The magnitude of the K(OC) values correlated strongly with the percentage of aromatic carbon in HS samples (r = 0.91). The hydrophobic binding was hypothesized as the key interaction underlying the binding of atrazine to HS.

[Ganglion block in cardiopulmonary bypass surgery]

Ganglion blockers increase the antinociceptive defense in anesthesiological support of cardiopulmonary bypass operations for mitral and aortic valve failure. Benzohexonium decreased total peripheral vascular resistance, increased cardiac and stroke indexes, and increased systolic potency of the heart. Ganglionar blocking was associated with an increase of systemic oxygen transport, arrhythmias developed rarely, blood concentrations of epinephrine, norepinephrine, ACTH, vasopressin, and leukinferon were lower.

[The effect of an invasion by Trichinella spiralis and Trichinella pseudospiralis on the ultrastructure of skeletal muscle tissue in the white mouse]

The ultrastructure of striated muscular tissue was studied in experiments with three groups of white mice: those infected with T. spiralis, T. pseudospiralis, and in those uninfected (controls). There was a heterogeneity of changes in the striated muscular tissue during 35-day infection. Deep damages to the contractile, trophic, energetic, supporting, and membranous apparatuses of muscle fibers are responsible for subcellular structural changes. At the same time compensatory and adaptative processes that reflect the hyperfunction of musculoskeletal tissue develop. Generally, T. spiralis causes focal ultrastructural changes while T. pseudospiralis induces diffuse ones.

[Changes in the blood oxygen capacity under the action of a permanent magnetic field]

The level of oxygen the blood was tested in 2 series of experiment on 20 dogs where the of apneic hypoxia is used. In addition in stand investigations (35 cases) with donor blood the content of oxygen in the blood was checked during and after combined influence to the blood the constant magnetic field (CMF) and oxygen. Peculiarity of alterations of oxygen blood capacity on conditions of influence CMF was the fact, that in 3 min. after CMF action only comparatively little surplus rise the part of oxygen connected with haemoglobin was seen; meanwhile the oxygen tension increased more than 1.5 times. It is reasonable to consider that under the conditions of CMF influence very short, unstable and upper than calculative level of connection oxygen and haemoglobin took place and after stopping the influence of CMF this oxygen translocated to the instant (soluble) part. It stimulated the growth of oxygen tension in the blood and ensured required level of the total oxygen balance of the body during hypoxia.

[Effect of prolonging the periods of endurance of mortal hypoxia during extracorporeal exposure to a magnetic field on the blood]

The influence of constant magnetic field to organism (through blood) during mortal hypoxia, combined with apnoea, was studied in 2 series of experiments in 38 dogs. It has been established that extracorporal influence of magnetic field to blood promotes 1.5 fold prolongation of animal's clinical death coming on the average after the cutting-off their breathing. Effect of prolongation of the mortal hypoxia sustaining periods was reached by complex influence of constant magnetic field (induction 0.1-0.5 TL) to circulated blood in extracorporal circuit with volume speed 20-25 ml/min/kg combined with short (2 min) inhalation of oxygen to lungs before apnoea.

[Placentitis induced by hepatitis viruses]

The results of morphological studies of 66 placentas from women suffering from various forms of viral hepatitis and HBs antigen carriers as well as results of a pathomorphological study of a late abortion, 3 stillborns and 2 newborns are presented. 33 placentas showed lymphocytic infiltration of varying degree and vasculitis. Of most importance were cellular changes, particularly in the decidua, with the appearance in the nuclei of inclusions similar to those found in the liver affected with viral hepatitis. A correlation is observed in some cases between liver changes in the mother, placental alterations and changes in the child.

[Trichinelliasis in western Podolia]

Situation with trichinosis in the Ternopol Province (Ukraine) in the period from 1962 to 1987 was studied. Muscle samples taken from 6695 animals of 20 species were investigated by the compressor method and by the method of digestion in artificial gastric juice. Trichinosis was detected in wolves, foxes, martens, ferrets, domestic dogs, cats and gray rats. In 1954--1979 39 trichinosis cases were registered in humans with 4 lethal cases. Domestic pigs proved to be the source of invasion. Since 1980 up to the end of investigation trichinosis cases have not been registered in people or in domestic pigs. Trichinosis invasion of wild, domestic and synanthropic mammals has decreased. Large work is being carried out to realize antitrichinosis measures.

[Noradrenaline content of the brain of rats of various ages following adaptation to a new situation and to the development of a passive avoidance conditioned reflex]

Noradrenaline (NA) levels in cortico-striatal (including cerebral cortex, hippocamp, striatum) and hypothalamo-brainstem (including hypothalamus, thalamus, tectum + tegmentum) regions were determined by fluorometry in I- and 2-month-old male rats after 7-day adaptation to experimental conditions and passive avoidance learning by single electric foot shock. Neither the new environment nor a week's adaptation to it resulted in any significant alteration of NA content in both brain regions of 1- and 2-month-old rats. No considerable differences in NA levels were found in rats of both age groups with and without passive avoidance responses. But 24 hours after the exposure to foot shock NA basal levels markedly decreased in both brain regions of 1-month-old rats, while in 2-month-old ones NA basal levels markedly increased in hypothalamo-brainstem region.

[Function of the adrenal cortex during elaboration of the passive avoidance conditioned reflex in immature rats]

Plasma 11-hydroxycorticosteroid (11-OHCS) levels were measured in 30-day-old rats by fluorometry during passive avoidance (PA) learning by means of a single electric footshock. In contrast to the data obtained in adult animals, pre-exposure of young rats for 7 days to the experimental environment (over 3 min daily) resulted in elevation of the basal 11-OHCS levels and in the lack of distinct changes in the hormonal background after placing the young rats into a chamber. As in previous experiments on adult rats, one day after PA learning the 11-OHCS levels were significantly lower in young rats displaying PA than in the animals which did not exhibit PA behavior. Five days after PA training these differences in adrenocortical reactivity disappeared, as was the case in adult animals.

[Adrenal cortical function in elaborating a passive avoidance conditioned reflex in rats adapted to experimental conditions]

Fluorometry was used to determine the content of 11-hydroxycorticosteroids (11-HCS) in the blood plasma of 2-month-old male rats in the course of passive avoidance learning by means of single electrocutaneous irritation (ECI) of the limbs. Pre-exposure of the animals for 7 days to experimental environment (over 3 min daily) led to a distinct reduction of the basal content of 11-HCS which returned to the initial level after adaptation discontinuance. One day after ECI the content of 11-HCS in rats which learned passive avoidance, was appreciably lower as compared to that in the animals which failed to learn the behavioral task. Five days after ECI the differences in the content of the corticosteroids in the animals of the two groups were little pronounced. It appears that while using passive avoidance as a long-term memory model, account should be taken of both the behavioral and emotional responses.

[Adrenal cortical function in rats with traumatic shock following removal and deafferentation of the hypothalamus]

The 11-oxycorticosteroid (11-OCS) content was studied in the blood plasma of sham-operated rats, rats with intact, ablated and deafferentated medial-basal hypothalamus (MBH) in traumatic shock. There were no reliable differences in the 11-OCS basal level in various groups of rats. MBH ablation led to the reduction in the weight of adrenal and pituitary glands and MBH deafferentation -- to increase in the weight of the former. The 11-OCS level was reliably higher in traumatic shock of rats with complete MBH deafferentation than in sham-operated animals.