Degradation of a Model Mixture of PAHs by Bacterial-Fungal Co-Cultures

BACKGROUND

Bacteria and fungi are the most important soil organisms owing to their abundance and the key roles they play in the functioning of ecosystems. We examined possible synergistic and antagonistic effects during the degradation of polycyclic aromatic hydrocarbons (PAHs) by co-cultures of ascomycetes and a plant-growth-promoting bacterium.

METHODS

Bacteria and fungi were grown in a liquid nutrient medium supplemented with PAHs. The PAH degradations and the identification of metabolites were checked by high-performance liquid chromatography (HPLC). Enzymatic activities were measured spectrophotometrically using test substrates. All experimental treatments were analyzed using Excel 2019 (Microsoft Office 2019, USA).

RESULTS

The model system included the plant-growth-promoting rhizobacterium (PGPR) Azospirillum brasilense and one of the following ascomycetes: Fusarium oxysporum (plant pathogen), Talaromyces sayulitensis (rhizospheric fungus), Trichoderma viride (plant-growth-promoting fungus, PGPF), and Trichoderma harzianum (PGPF). The notable results are: (1) synergistic effects consisted of more active utilization of the PAH mixture compared to individual compounds, while the PAH mixture was more actively degraded by co-cultures than monocultures; (2) three effects of mutual influence by the studied organisms were also revealed: depressing (F. oxysporum and A. brasilense), partially depressing (T. sayulitensis suppressed the growth of A. brasilense but increased the degradation of anthracene, pyrene, and fluoranthene), and positive effects (A. brasilense and T. viride or T. harzianum); (3) for the first time quinone metabolites of PAH degradation and extracellular oxidase and peroxidase were produced during PAH degradation by T. sayulitensis.Conclusions: The results of the study contribute to the understanding of bacterial-fungal interactions in polluted settings.

Effect of Heavy-Metal-Resistant PGPR Inoculants on Growth, Rhizosphere Microbiome and Remediation Potential of Miscanthus × giganteus in Zinc-Contaminated Soil

Microbial-assisted phytoremediation is considered a more effective approach to soil rehabilitation than the sole use of plants. Mycolicibacterium sp. Pb113 and Chitinophaga sp. Zn19, heavy-metal-resistant PGPR strains originally isolated from the rhizosphere of Miscanthus × giganteus, were used as inoculants of the host plant grown in control and zinc-contaminated (1650 mg/kg) soil in a 4-month pot experiment. The diversity and taxonomic structure of the rhizosphere microbiomes, assessed with metagenomic analysis of rhizosphere samples for the 16S rRNA gene, were studied. Principal coordinate analysis showed differences in the formation of the microbiomes, which was affected by zinc rather than by the inoculants. Bacterial taxa affected by zinc and the inoculants, and the taxa potentially involved in the promotion of plant growth as well as in assisted phytoremediation, were identified. Both inoculants promoted miscanthus growth, but only Chitinophaga sp. Zn19 contributed to significant Zn accumulation in the aboveground part of the plant. In this study, the positive effect of miscanthus inoculation with Mycolicibacterium spp. and Chitinophaga spp. was demonstrated for the first time. On the basis of our data, the bacterial strains studied may be recommended to improve the efficiency of M. × giganteus phytoremediation of zinc-contaminated soil.

Natural and Technical Phytoremediation of Oil-Contaminated Soil

Natural and technical phytoremediation approaches were compared for their efficacy in decontaminating oil-polluted soil. We examined 20 oil-contaminated sites of 800 to 12,000 m² each, with different contamination types (fresh or aged) and levels (4.2-27.4 g/kg). The study was conducted on a field scale in the industrial and adjacent areas of a petroleum refinery. Technical remediation with alfalfa (Medicago sativa L.), ryegrass (Lolium perenne L.), nitrogen fertilizer, and soil agrotechnical treatment was used to clean up 10 sites contaminated by oil hydrocarbons (average concentration, 13.7 g/kg). In technical phytoremediation, the per-year decontamination of soil was as high as 72-90%, whereas in natural phytoremediation (natural attenuation with native vegetation) at 10 other oil-contaminated sites, per-year decontamination was as high as that only after 5 years. Rhizodegradation is supposed as the principal mechanisms of both phytoremediation approaches.

THE STUDY OF THE IMMUNE STATUS IN POST-COVID SYNDROME BY FLOW CYTOMETRY

A novel coronavirus infection was described in 2019 in Wuhan, China. From the first months of the spread of the infection around the world, evidence began to appear that patients after recovery had various symptoms. Duration, intensity, and variability of symptoms vary among patients and are often not associated with the severity of the most acute illness. Recently the concept of post-COVID syndrome (post-COVID or long-COVID in the English-language literature) has acquired increasingly clear diagnostic criteria. Persistent symptoms and / or the appearance of delayed complications after 4 weeks or more from the onset of symptoms of an acute illness are commonly called post-COVID syndrome. The wide range of symptoms that can occur in patients with post-COVID syndrome is now a major health concern worldwide. A proper clinical evaluation will help determine the etiology and build a treatment plan. Longer studies aimed at identifying the effects of COVID-19, possible risk factors for their development, a detailed study of the pathogenetic mechanisms of SARS-CoV-2, and the development of treatment and rehabilitation methods to improve the mental and physical health of surviving patients are relevant elements of study for the foreseeable future. T-lymphocytes are a poorly studied population of T lymphocytes. These cells are more often localized in the mucous membranes of the body which have the properties of innate and acquired immunity. The main biological functions are cytolysis, immunoregulation which indicates an important immunocompetent role of this type of cell population in severe infectious diseases. This article provides information on the fraction of T-lymphocytes during the formation of adaptive immunity in patients with post-COVID syndrome.

PROGNOSTIC EVALUATION OF LABORATORY BLOOD PARAMETERS IN SEPTIC PATIENTS OF INTENSIVE CARE UNIT

Sepsis is a serious disease accompanied by the development of a systemic inflammatory response syndrome. The informativeness of existing diagnostic markers of sepsis at various stages of its development remains controversial. Research into septic conditions has led to significant progress in determining the body’s response to infection. The search for laboratory indicators capable of indicating the prognosis of the disease is an important diagnostic criterion in the timely treatment and prevention of sepsis in hospital treatment. The publication presents data from a survey of the studied changes in arterial blood parameters in septic patients with a prognostic assessment. The indicators of biomarkers of inflammation in septic patients were analyzed, the tinctorial and other bacteriological properties of pathogens in the development of generalized sepsis were evaluated, the components influencing the favorable and unfavorable outcome of the disease were determined in the research. The identification of laboratory parameters that help to give the real assessment of the severity and prognosis of the disease in patients of the intensive care unit in a timely manner will allow you to choose effective treatment methods, timely adjust the prescribed therapy and reduce the number of deaths.

Effect of remediation techniques on petroleum removal from and on biological activity of a drought-stressed Kastanozem soil

Many petroleum extraction and refinement plants are located in arid climates. Therefore, the remediation of petroleum-polluted soils is complicated by the low moisture conditions. We ran a 70-day experiment to test the efficacy of various combining of remediation treatments with sorghum, yellow medick, and biochar to remove petroleum from and change the biological activity of Kastanozem, a soil typical of the dry steppes and semideserts of the temperate zone. At normal moisture, the maximum petroleum-degradation rate (40%) was obtained with sorghum-biochar. At low moisture, the petroleum-degradation rate was 22 and 30% with yellow medick alone and with yellow medick - sorghum, respectively. Biochar and the biochar-plant interaction had little effect on soil remediation. Both plants promoted the numbers of soil microbes in their rhizosphere: yellow medick promoted mostly hydrocarbon-oxidizing microorganisms, whereas sorghum promoted both hydrocarbon-oxidizing and total heterotrophic microorganisms. Low moisture did not limit microbial development. In the rhizosphere of sorghum, dehydrogenase and urease activities were maximal at normal moisture, whereas in the rhizosphere of yellow medick, they were maximal at low moisture. Peroxidase activity was promoted by the plants in unpolluted soil and was close to the control values in polluted soil. Biochar and the biochar-plant interaction did not noticeably affect the biological activity of the soil.

Physiological and biochemical characteristic of Miscanthus × giganteus grown in heavy metal - oil sludge co-contaminated soil

The effect of oil sludge and zinc, present in soil both separately and as a mixture on the physiological and biochemical parameters of Miscanthus × giganteus plant was examined in a pot experiment. The opposite effect of pollutants on the accumulation of plant biomass was established: in comparison with uncontaminated control the oil sludge increased, and Zn reduced the root and shoot biomass. Oil sludge had an inhibitory effect on the plant photosynthetic apparatus, which intensified in the presence of Zn. The specific antioxidant response of M. × giganteus to the presence of both pollutants was a marked increase in the activity of superoxide dismutase (mostly owing to oil sludge) and glutathione-S-transferase (mostly owing to zinc) in the shoots. The participation of glutathione-S-transferase in the detoxification of both the organic and the inorganic pollutants was assumed. Zn inhibited the activity of laccase-like oxidase, whereas oil sludge promoted laccase and ascorbate oxidase activities. This finding suggests that these enzymes play a part in the oxidative detoxification of the organic pollutаnt. With both pollutants used jointly, Zn accumulation in the roots increased 6-fold, leading to increase in the efficiency of soil clean-up from the metal. In turn, Zn did not significantly affect the soil clean-up from oil sludge. This study shows for the first time the effect of co-contamination of soil with oil sludge and Zn on the physiological and biochemical characteristics of the bioenergetic plant M. × giganteus. The data obtained are important for understanding the mechanisms of phytoremediation with this plant.

Study of Boraginaceae plants for phytoremediation of oil-contaminated soil

Long-term field observations of the natural vegetation cover in industrial and adjacent areas has revealed that the Boraginaceae was one of the main plant family representatives of which were noted in oil-contaminated area. In this study against the background of the previously well characterized plant families Poaceae and Fabaceae, the phytoremediation potential of Boraginaceae plants was investigated under the field conditions and described. Among the members of this family, Lithospermum arvense, Nonea pulla, Asperugo procumbens, Lappula myosotis, and Echium vulgare were the most common in oil-contaminated areas. N. pulla was the most tolerant to hydrocarbons and, along with L. arvense and E. vulgare, actively stimulated the soil microorganisms, including hydrocarbon-oxidizing ones, in their rhizosphere. A comparative assay confirmed that the plants of the Fabaceae family as a whole more efficiently enrich the soil both with available nitrogen and with pollutant degradation genes. Nevertheless, the comparatively high ammonium nitrogen content in the rhizosphere of N. pulla and E. vulgare allows these species to be singled out to explain their high rhizosphere effect, and to suggest their remediation potential for oil-contaminated soil.Novelty statement Against the background of the previously well characterized plant families Poaceae and Fabaceae, the remediation potential of Boraginaceae plants was described for the first time. Overall, this study contributes to understanding the differences in remediation potential of plants at the family level and suggests the monitoring pollutant degradation genes as an informative tool to the search for plant promising for use in the cleanup of oil-contaminated soil.

Combined effects of cadmium and oil sludge on sorghum: growth, physiology, and contaminant removal

The physiological and biochemical responses of Sorghum bicolor (L.) Moench. to cadmium (Cd) (30 mg kg^-1) and oil sludge (OS) (16 g kg^-1) present in soil both separately and as a mixture were studied in pot experiments. The addition of oil sludge as a co-contaminant decreased Cd entry into the plant by almost 80% and simultaneously decreased the stimulation of superoxide dismutase (SOD) and peroxidase. The decrease in glutathione reductase (GR) activity and the increase in glutathione-S-transferase (GST) activity under the influence of oil sludge indicated that its components were detoxified by conjugation with glutathione. Cd additionally activated the antioxidant and detoxifying potential of the plant enzymatic response to stress. This helped to enhance the degradation rate of oil sludge in the rhizosphere, in which the participation of the root-released enzymes in the degradation could be possible. Cd increased the extent of soil clean-up from oil sludge, mainly owing to the elimination of paraffins, naphthenes, and mono- and bicyclic aromatic hydrocarbons. The mutual influence of the pollutants on the biochemical responses of sorghum and on soil clean-up was evaluated. The results are important for understanding the antistress and detoxification responses of the remediating plant to combined environmental pollution.

Dynamics of natural revegetation of hydrocarbon-contaminated soil and remediation potential of indigenous plant species in the steppe zone of the southern Volga Uplands

The result of monitoring of natural vegetation growing on oil-contaminated (2.0-75.6 g/kg) and uncontaminated (0.04-2.0 g/kg) soils of a petroleum refinery for a period of 13 years is presented. Floristic studies showed that the families Poaceae, Asteraceae, Fabaceae, and eventually Brassicaceae were predominant in the vegetation cover of both types of soils. Over time, the projective vegetation cover of the contaminated sites increased from 46 to 90%; the species diversity increased twofold: in the ecological-cenotic structure of the flora, the number of ruderal plant species decreased; and the number of steppe, i.e., zonal, plant species increased. Using 62 dominant plant species, we conducted a field study of plant characteristics such as resistance to oil pollution, the ability to enrich the rhizosphere soil with microorganisms and bioavailable mineral nitrogen, and reduction of the concentration of petroleum hydrocarbons. The results enable us to characterize the phytoremediation potential (PRP) of the native plants and identify species that, probably, played a key role in the natural restoration of oil-contaminated soils. Statistical analysis showed correlations between the PRP constituents, and the leading role of rhizosphere microorganisms in the rhizodegradation of petroleum hydrocarbons was proven. A conditional value of PRP was proposed which allowed the investigated plants to be ranked in 11 classes. The study of a large sample of plant species showed that some plants held promise for the use in reclamation of soils in arid steppe zone, and that other species can be used for the rehabilitation of saline soils and semideserts.

Peroxidases from root exudates of Medicago sativa and Sorghum bicolor: Catalytic properties and involvement in PAH degradation

Peroxidases from root exudates of sorghum (Sorghum bicolor L. Moench) and alfalfa (Medicago sativa L.) were purified and characterized, and their ability to oxidize native PAHs and PAH-derivatives was evaluated. The obtained data confirm that peroxidases are involved in the rhizosphere degradation of PAHs. Nondenaturing PAGE showed that the peroxidases of both plants were represented by a range of isoforms/isoenzymes (five to eight). Minor forms were lost during further purification, and as a result, the major anionic form from alfalfa root exudates and the major cationic form from those of sorghum were obtained. Both electrophoretically homogeneous peroxidases were monomeric proteins with a molecular weight of about 46-48 kDa. The pH optima and the main catalytic constants for the test substrates were determined. On the basis of their molecular and catalytic properties, the obtained enzymes were found to be typical plant peroxidases. Derivatives of PAHs and potential products of their microbial degradation (9-phenanthrol and 9,10-phenanthrenequinone), unlike the parent PAH (phenanthrene), inhibited the catalytic activity of the peroxidases, possibly indicating greater availability of the enzymes' active centers to these substances. Peroxidase-catalyzed decreases in the concentrations of a number of PAHs and their derivatives were observed. Sorghum peroxidase oxidized anthracene and phenanthrene, while alfalfa peroxidase oxidized only phenanthrene. 1-Hydroxy-2-naphthoic acid was best oxidized by peroxidase of alfalfa. However, quinone derivatives of PAHs were unavailable to sorghum peroxidase, but were oxidized by alfalfa peroxidase. These results indicate that the major peroxidases from root exudates of alfalfa and sorghum can have a role in the rhizosphere degradation of PAHs.

Comparison of the phytoremediation potentials of Medicago falcata L. And Medicago sativa L. in aged oil-sludge-contaminated soil

Thirteen-year monitoring of the vegetation growing in the industrial and adjacent areas of an oil refinery showed the prevalence of yellow medick (Medicago falcata L.) over other plant species, including alfalfa (Medicago sativa L.). A comparative field study of the two Medicago species established that yellow medick and alfalfa exhibited similar resistance to soil petroleum hydrocarbons and that the pollutant concentration in their rhizosphere was 30% lower than that in the surrounding bulk soil. In laboratory pot experiments, yellow medick reduced the contaminant content by 18% owing to the degradation of the major heavy oil fractions, such as paraffins, naphthenes, and alcohol and benzene tars; and it was more successful than alfalfa. Both species were equally effective in stimulating the total number of soil microorganisms, but the number of hydrocarbon-oxidizing microorganisms, including polycyclic aromatic hydrocarbon degraders, was larger in the root zone of alfalfa. In turn, yellow medick provided a favorable balance of available nitrogen. Both Medicago species equally stimulated the dehydrogenase and peroxidase activities of the soil, and yellow medick increased the activity of soil polyphenol oxidase but reduced the activity of catalase. The root tissue activity of catalase, ascorbate oxidase, and tyrosinase was grater in alfalfa than in yellow medick. The peroxidase activity of plant roots was similar in both species, but nondenaturing polyacrylamide gel electrophoresis showed some differences in the peroxidase profiles of the root extracts of alfalfa and yellow medick. Overall, this study suggests that the phytoremediation potentials of yellow medick and alfalfa are similar, with some differences.

Effect of cadmium stress and inoculation with a heavy-metal-resistant bacterium on the growth and enzyme activity of Sorghum bicolor

In this study, the influence of the heavy-metal-resistant rhizobacterial inoculant Rhodococcus ruber N7 on the growth and enzyme activity of Sorghum bicolor (L.) Moench. under cadmium stress was investigated in quartz sand pot experiments. The effect of cadmium and bacterium on the plant biomass accumulation, photosynthetic pigments, protein content, and the activities of plant-tissue enzymes such as peroxidase, laccase, and tyrosinase were estimated. It was shown that the presence of cadmium in the sand influenced the roots to a greater extent than it influenced the aerial parts of sorghum. This is manifested as increased protein content, reduced activity of peroxidase, and increased activity of laccase. Compared with cadmium stress, inoculation of plants with rhizobacterium R. ruber N7 has a stronger (and often opposite) effect on the biochemical parameters of sorghum, including a decrease in the concentration of protein in the plant, but increased the activity of peroxidase, laccase, and tyrosinase. Under cadmium contamination of sand, R. ruber N7 successfully colonizes the roots of Sorghum bicolor, survives in its root zone, and contributes to the accumulation of the metal in the plant roots, thereby reducing the concentration of the pollutant in the environment.

The coupling of the plant and microbial catabolisms of phenanthrene in the rhizosphere of Medicago sativa

We studied the catabolism of the polycyclic aromatic hydrocarbon phenanthrene by four rhizobacterial strains and the possibility of enzymatic oxidation of this compound and its microbial metabolites by the root exudates of alfalfa (Medicago sativa L.) in order to detect the possible coupling of the plant and microbial metabolisms under the rhizospheric degradation of the organic pollutant. A comparative study of phenanthrene degradation pathways in the PAH-degrading rhizobacteria Ensifer meliloti, Pseudomonas kunmingensis, Rhizobium petrolearium, and Stenotrophomonas sp. allowed us to identify the key metabolites from the microbial transformation of phenanthrene, including 9,10-phenanthrenequinone, 2-carboxybenzaldehyde, and 1-hydroxy-2-naphthoic, salicylic, and o-phthalic acids. Sterile alfalfa plants were grown in the presence and absence of phenanthrene (0.03 g kg(-1)) in quartz sand under controlled environmental conditions to obtain plant root exudates. The root exudates were collected, concentrated by ultrafiltration, and the activity of oxidoreductases was detected spectrophotometrically by the oxidation rate for various substrates. The most marked activity was that of peroxidase, whereas the presence of oxidase and tyrosinase was detected on the verge of the assay sensitivity. Using alfalfa root exudates as a crude enzyme preparation, we found that in the presence of the synthetic mediator, the plant peroxidase could oxidize phenanthrene and its microbial metabolites. The results indicate the possibility of active participation of plants in the rhizospheric degradation of polycyclic aromatic hydrocarbons and their microbial metabolites, which makes it possible to speak about the coupling of the plant and microbial catabolisms of these contaminants in the rhizosphere.

Oxidoreductase activity of Sorghum root exudates in a phenanthrene-contaminated environment

The effect of the polycyclic aromatic hydrocarbon (PAH) phenanthrene on the enzymatic activity of root exudates of the phytoremediating plant Sorghum bicolor (L.) Moench was studied. Analysis of sorghum root exudates allowed us to reveal the activities of oxidase, peroxidase, and tyrosinase. The activities of these enzymes were progressive as the soil phenanthrene concentration increased. Using lyophilized samples, we found that as a result of the enzymatic activity of the root exudates, some of the PAHs and products of PAH degradation were oxidized in the reaction mixture supplemented with the mediating agents (ABTS or DL-DOPA) but that no oxidation was observed in the reaction mixtures without the mediators. The revealed enzymatic activity of the sorghum root exudates may indicate the involvement of the root-released oxidoreductases in rhizospheric degradation of PAHs and/or their derivatives. In addition, from the data obtained, the coupling of plant and microbial metabolisms of PAHs in the rhizosphere may be surmised.

Rhizosphere microflora of plants used for the phytoremediation of bitumen-contaminated soil

The microbial communities and their degradative potential in rhizospheres of alfalfa (Medicago sativa) and reed (Phragmites australis) and in unplanted soil in response to bitumen contamination of soil were studied in pot experiments. According to the results of fluorescence microscopy, over a period of 27 months, bitumen contamination of soil reduced the total number of microorganisms more significantly (by 75%) in unplanted than in rhizosphere soil (by 42% and 7% for reed and alfalfa, respectively) and had various effects on some important physiological groups of microorganisms such as actinomycetes as well as nitrogen-fixing, nitrifying, denitrifying, ammonifying, phosphate-solubilizing, sulphur-oxidizing, cellulolytic and hydrocarbon-degrading microorganisms. The changes in the physiological structure of the microbial community under bitumen contamination were found to hinge on not merely the presence of plants but also their type. It was noted that the rhizosphere microflora of alfalfa was less inhibited by hydrocarbon pollution and had a higher degradative potential than the rhizosphere microflora of reed.

Plant--rhizosphere-microflora association during phytoremediation of PAH-contaminated soil

The capability of plants to promote the microbial degradation of pollutants in rhizosphere soil is a principal mechanism of phytoremediation of PAH-contaminated soil. The formation of a specific rhizosphere microbocenosis with a high degradative potential toward contaminants is largely determined by plant species. The comparative PAH-degradation in unplanted soil and in soil planted with reed (Phragmites australis) and alfalfa (Medicago sativa) was studied in pot experiments during 2 years. Both alfalfa and reed successfully remediated contaminated soil by degrading 74.5 and 68.7% of PAHs, respectively. The study of the rhizosphere, rhizoplane, and unplanted-soil microflora in experimental pots showed that alfalfa stimulated the rhizosphere microflora of PAH-contaminated soil more effectively than did reed. Alfalfa clearly enhanced both the total number of microorganisms (1.3 times, according to fluorescence microscopy data) and the rate of the PAH-degrading population (almost seven times, according to plate counting). The degradative potential of its rhizosphere microflora toward PAHs was higher than the degradative activity of the reed rhizosphere. This study provides relevant information for the successful application of alfalfa to phytoremediate PAH-contaminated soil.