Hydrocarbon-oxidizing Bacteria Research Articles

Study of biotechnological potential of hydrocarbon-oxidizing bacteria from oil-contaminated soils of the Uzen oil field

Background: Oil-contaminated soils are one of the significant environmental concerns in Western Kazakhstan. Cleaning soils from oil contamination is becoming extremely important. Biological soil treatment, which uses hydrocarbon-oxiding bacteria for microbiological remediation, is a more environmentally friendly and delicate method of soil treatment than any other currently used technology (physical, chemical, biological). One of the important aspects of microbiological remediation is the use of bacteria endomimic to the treated soil. This guarantees the most effective soil purification, as the bacteria perform in relatively optimal conditions for themselves. The soil of the Mangistau region, especially the coastal regions, is distinctive due to its high mineralisation and low moisture content, which have helped to form a specific microflora that is adapted to these conditions. Aim: The study aims to search and isolate highly effective hydrocarbon-oxidizing bacteria that are native to highly mineralized soils of the Uzen oil field. Materials and methods: The research employs a variety of analytical techniques, including water chemistry analysis and infrared spectrometry, as well as the microbiological culture of aerobic bacteria on liquid and dense media in environments (temperature and salinity) that closely resemble their native ecotopes. Results: Four enrichment cultures of hydrocarbon-oxidizing bacteria were obtained, and three pure cultures of oil-oxidizing bacteria were isolated. Their hydrocarbon-oxidizing efficiency has been studied. On the basis of heavy, extremely viscous paraffinic oil from the Uzen field, their hydrocarbon-oxidizing efficiency was examined. Conclusion: In this study, active enrichment cultures of halophilic hydrocarbon-oxidizing bacteria as well as active accumulative cultures of halophilic and moderately thermophilic aerobic bacteria were obtained. These bacteria are capable of oxidising a wide range of hydrocarbons, including high-molecular polycyclic and sulfur-containing compounds. Their high biotechnological potential will be studied in further studies.

Analysis of spatial structure and singularity of microbial biogeochemical anomalies in the Taiwan Strait Basin

The abundance of specific hydrocarbon-oxidizing bacteria (MV value) in surface soil is closely linked to the concentration of thermogenic light hydrocarbons found in the underlying layers. The identification of these bacteria using specific detection techniques offers unique insights into microbiological anomalies associated with oil and gas, underscoring the significance of delineating microbiological geochemical anomalies in the exploration process. Accurate determination of the anomaly range is crucial for forecasting potential oil and gas reservoirs. In this study, a variety of fractal and geological statistical methods were employed to analyze microbiological geochemical data from the Taiwan Strait Basin. The multifractal approach allows for the simultaneous assessment of spatial autocorrelation and singularity in geochemical fields, with the fractal distribution reflecting the localized enrichment and depletion patterns of microbiological geochemical elements in rocks and other substrates. Geological statistical methods, such as the variation function, enable the assessment of spatial autocorrelation in geochemical and geophysical fields. The results indicate that microbiological anomalies in the Jiulongjiang Depression are mainly concentrated in the southwestern part of the study area, with some anomalies also observed in the central region. Conversely, microbiological anomalies in the Jinjiang Depression are predominantly located in the southern portion of the study area. Microbiological anomalies in the study area (Jinjiang Depression and Jiulongjiang Depression) exhibit a northeast-southwest strip distribution, aligning with the trend of the depressions and faults, suggesting that faults could influence the distribution of oil and gas resources in the region. Based on microbiological statistical analyses, the Jiulongjiang Depression shows better potential for oil and gas prospects compared to the Jinjiang Depression, guiding future research efforts in the Jiulongjiang Depression.

SEASONAL DYNAMICS OF CHEMICAL AND MICROBIOLOGICAL CHARACTERISTICS OF BOTTOM SEDIMENTS IN THE SEA ESTUARY OF A SMALL RIVER IN THE SEVASTOPOL REGION (BY THE EXAMPLE OF THE CHERNAYA RIVER, CRIMEA)

The annual dynamics of (1) chloroform-extractable substances (CES) and petroleum hydrocarbons (PH) in riverside fluvial sediments, in the bottom sediments of the mixing zone of river and sea waters, and in the bottom sediments of the marine area, and (2) the abundance of hydrocarbon-oxidizing (HOB) and heterotrophic (HB) bacterial groups in the bottom sediments of the marine area and riverside sediments is analysed. The maximal content of CES was found in the marine area (450±17.5 mg/100 g), and the minimal one - in the river part (127.6±10.9 mg/100 g), in the mixing zone of river and sea waters - 370±37.9 mg/100 g. The average concentrations of PH are distributed similarly to the concentrations of CES: the maximal values (127.5±10.9 mg/100 g) are detected in marine ground, the values for the sediments of the mixing zone are slightly lower (103.1±9.4 mg/100 g), and the minimal values (54.8±23.9 mg/100 g) are detected in river sediments. The physicochemical characteristics of bottom and coastal sediments are presented. The abundance of HB in the bottom sediments of the marine area varied from 7.5•103 to 2.5•106 cells/g, respectively, and from 9.5•103 to 9.5•108 cells/g in the river area. There was no seasonal variability in the abundance of HB at both areas. Hydrocarbon-oxidizing bacteria were registered in 100 % of the samples of bottom and riverside sediments of the designated water areas. The abundance of HOB varied from 25 to 2.5•104 cells/g in the marine zone and from 25 to 4.5•103 cells/g in the river zone. The maximal values of HOB abundance in the riverside sediments were recorded during the flood period (February-April).

Progress of Crude Oil Gasification Technology Assisted by Microorganisms in Reservoirs.

Crude oil gasification bacteria, including fermenting bacteria, hydrocarbon-oxidizing bacteria, reducing bacteria, and methanogenic bacteria, participate in multi-step reactions involving initial activation, intermediate metabolism, and the methanogenesis of crude oil hydrocarbons. These bacteria degrade crude oil into smaller molecules such as hydrogen, carbon dioxide, acetic acid, and formic acid. Ultimately, they convert it into methane, which can be utilized or stored as a strategic resource. However, the current challenges in crude oil gasification include long production cycles and low efficiency. This paper provides a summary of the microbial flora involved in crude oil gasification, the gasification metabolism pathways within reservoirs, and other relevant information. It specifically focuses on analyzing the factors that affect the efficiency of crude oil gasification metabolism and proposes suggestions for improving this efficiency. These studies deepen our understanding of the potential of reservoir ecosystems and provide valuable insights for future reservoir development and management.

Effectiveness of biogeosorbents based on mineral carriers for treatment oil-contaminated soil

Methods for cleaning oil-contaminated areas include the use of sorbents, the effectiveness of which is enhanced by the immobilization of hydrocarbon-oxidizing microorganisms on their surface. Biogeosorbents are obtained on the basis of mineral raw materials (analcime- and glauconite-containing rocks and thermally activated vermiculite) and hydrocarbon-oxidizing bacteria of the genera Pseudomonas and Microbacterium extracted from contaminated soils of the Murmansk region. The number of immobilized bacteria on the studied carriers remains high throughout 9 months of storage, and the bacterial film on the surface of mineral carriers persists for 12 months of storage in an air-dry state. When storing biogeosorbents, no special conditions or additional preparation are required before use. Mineral carriers have a stimulating effect on the height of seedlings and the length of roots of test plants. When biogeosorbents are added, the number of bacteria capable of microbiological transformation of petroleum products increases, and the degree of soil purification from petroleum hydrocarbons at the initial stage (during the first 30 days) increases. The most effective is the introduction of thermally activated vermiculite and glauconite-containing rock with immobilized hydrocarbon-oxidizing bacteria. The use of a biogeosorbent based on thermally activated vermiculite can reduce the cleaning time to 20–22 months, and based on glauconite-containing rock – up to 17 months, while without treatment this period will be at least 29 months.

Accelerated technology for cleaning oil-contaminated soils

Relevance. The uniqueness of the practical application of accelerated and environmentally safe technology for the reclamation of oil–polluted lands, which uses local mineral raw materials, a consortium of autochthonous hydrocarbon-oxidizing bacteria with multifunctional positive properties, effective phytomeliorants, is theoretically substantiated. Hydrocarbon pollution is eliminated directly at the spill site, and the rate ofreturn of disturbed soils to agricultural circulation is 3–4 times faster than traditional methods.Methods. Objects of research: mechanically activated bentopowder and nanobentonite, a consortium of hydrocarbon-oxidizing bacteria composed of three autochthonous strains, soil leached chernozem, spring wheat, Devonian oil. The concentration of oil pollution at the site was 6.4%. Bentopowder and nanobentonite were introduced in doses of 6.0 t/ha and 0.3 t/ha, respectively. Sampling was carried out with a sampler on the 0th, 15th, 30th, and 90th days.Results. The optimal doses of application of bento powder and nano bentonite to disturbed soil above the average pollution level (6.0 t/ha and 0.3 t/ha respectively) are recommended. After 15 days, the level of contamination is halved (to 51.1 g/kg and 40.8 g/kg with benton powder and nanobentonite respectively). Removal of the introduced mineral sorbent is not required, since it later becomes a source of mineral nutrition for autochthonous microorganisms-destructors and a soil improver. At the second innovative stage, a consortium formed from effective strains and adapted to specific conditions is used. The strains of the consortium fit into an ecological niche, adapt and begin to actively develop, utilizing oil and petroleum products. After a month, the level of contamination decreases to 19.2 g/kg and 9.2 g/kg with the addition of benton powder and nanobentonite respectively.

Комплексная оценка экологического состояния участка трансграничной реки Нарвы

A comprehensive study of the ecological state on the transboundary Narva River (Russia –Estonia border) downstream of Ivangorod, Kingisepp District, Leningrad Region, was carried out. It included the determination of chemical indicators of pollution of the natural river water, with an emphasis on some heavy metals content in water, sediments and soft tissues of local filter-feeding mollusks; the latter were used as bioindicators of river pollution in this location. Zn was determined in maximum concentrations in bottom sediments, then Cu, to a lesser extent Pb, Cd and Ni. The coefficient of metal bioconcentration calculated in soft tissues of mollusks showed maximum for Zn and Cu, to a lesser extent for Pb, Cd and minimum for Ni. However, such values have no negative effect on local biota as shown by physiological testing of bivalves from study site. The functional assessment of bivalves by non-invasive cardiac rhythm recording made it possible to characterize their functional status and adaptive capabilities as good. The relative abundance of hydrocarbon-oxidizing bacteria in the digestive tract of mollusks from the Narva River has been determined as an indicator of environmental pollution by oil products. It was noted that the number of hydrocarbon-oxidizing bacteria does not exceed the values characteristic of the reference waters of the Eastern Gulf of Finland. Based on the totality of the studies, it was concluded that the river waters in the studied location can be characterized as slightly polluted and its ecological status as of a good quality.

Оценка качества воды и донных отложений Северо-Крымского канала перед запуском основного потока воды по содержанию углеводородов и некоторым микробиологическим показателям (весна 2022 г., полуостров Крым)

In the Spring 2014, the supply of Dnieper water to the North Crimean Canal (NCC) was stopped. The canal was previously used for centralized water supply and agriculture in the steppe part of Crimea. After 8 years, the active use of the Dnieper water in the Crimea requires comprehensive studies of its quality. Traditionally, microbiological studies are used to assess the ecological condition of water areas. In addition, it is important to monitor components of hydrocarbon origin such as aliphatic hydrocarbons. In general, the NCC waters by microbiological parameters (the number of heterotrophic, lipolytic and hydrocarbon-oxidizing bacteria) and the concentration of hydrocarbons can be attributed to the oligosapropic, low-polluted zone. According to the level of aliphatic hydrocarbons, the bottom sediments of the studied section of the NCC and the soil in the area adjacent to the canal are classified as naturally pure.

Response of the rhizosphere microbial community of phytoremediation plants to oil pollution and the application of biopreparations

The present study aims to evaluate microbiological activity in the rhizosphere of plants growing under oil pollution conditions and in the presence of biopreparations having a different spectrum of action. Common sunflower (Helianthus annuus L.) and crested wheatgrass (Agropyron cristatum L.) were selected as phytoremediation plants. The soil was treated with the hydrocarbon-oxidizing preparation “Lenoil” and two preparations of nonspecific action having a growth-stimulating effect: “Elena” and “Azolen”. A soil pollutant concentration of 4% was selected for conducting plant-based bioremediation. The study showed a slight increase in the total microbial count and the microscopic fungi count in the rhizosphere of plants due to pollution, while indicating a decrease in the count of amino-autotrophs and cellulolytics. The introduction of non-specific biopreparations into the soil promoted the growth of destructive microorganisms despite the fact that microorganisms in the preparations are not designed for soil detoxification and decontamination. Under the effect of biopreparations, the rhizosphere of sunflower and wheatgrass plants exhibited an increase or stabilization of microbiological activity, which may indicate their positive effect on microbiological processes occurring in contaminated soil. The rhizosphere of Agropyron cristatum L. plants generally provided a more favorable environment for the development of such groups of bacteria as amino-autotrophs, cellulolytics, micromycetes, and hydrocarbon-oxidizing bacteria. Of the studied variants of soil treatment with biopreparations for phytoremediation purposes, it is recommended to combine the application of the “Lenoil” biopreparation and the planting of phytoremediation plants in oil-contaminated soil.

Novel Use of Microbial Hydrocarbon Detection Technology in Reducing the Risk of Nonhydrocarbon Exploration in Oil and Gas Exploration in the South China Sea

Summary As the exploration of the South China Sea continues into deeper water, the chances of encountering nonhydrocarbon gas (CO2, N2, etc.) reservoirs rise. The question of how to avoid the risks associated with the discovery of nonhydrocarbon gas reservoirs becomes an issue for deepwater (DW) oil and gas exploration. Geomicrobial hydrocarbon detection (GMHD) is a nonseismic hydrocarbon detection technology that is able to predict the hydrocarbon potential of a prospective area at depth. This is accomplished via the detection of specific hydrocarbon-oxidizing bacteria in both onshore soils and offshore sea bottom sediment samples. The effectiveness of this method has been proved repeatedly in DW explorations of the northern South China Sea. It documents a possible solution to nonhydrocarbon gas risk prediction by combining the oil and gas prediction results of geomicrobial hydrocarbon detection with results from geological and geophysical studies to analyze the different microbial responses above nonhydrocarbon gas and hydrocarbon gas reservoirs. This was verified in the DW exploration practices undertaken in the Pearl River Mouth Basin and Qiongdongnan Basin of South China Sea.

Chemical and Microbiological Composition of Tom River Bottom Sediments (Yurginskii District, Western Siberia)

Data of chemical and microbiological analyses of bottom sediment composition of the Tom R. near Yurga Town, Kemerov oblast, are given. All samples of bottom sediments were found to contain organic compounds of mixed, biogenic, and anthropogenic origin with the predominance of the latter. Clayey and silty bottom sediments show a higher content of ash-free substance, heavy metals, practically all classes of identified hydrocarbons, except for oxygen-containing and acyclic compounds. Bottom sediments with sand composition contain minimal concentrations of organic pollutants, and the proportions of hydrocarbons of different origin in them are comparable. Microbiological analysis showed the predominance of hydrocarbon-oxidizing bacteria in bottom sediments composed of clays and silty sand.

Ecological Assessment of Drilling Sludge and Development of a Method for their Bioremediation in Western Siberia

The article considers the issue of bioremediation of drilling sludge. The aim of the research is studying of the microbiological processes occurring in soils based on drilling sludge, with their subsequent application for the biological stage of reclamation of disturbed lands. Microbiological characteristics of drilling sludge and four samples of soils based on it with the addition of diatomite, dolomite flour, peat, gypsum, glauconite, humic preparation Rostock in different proportions were studied. Crops were shown on agarized medium: meat-peptone agar (MPA), starch-ammonia agar (SAA), Munz medium, Chapek medium, depending on the determined group of microorganisms. The total number of microflora, the number of saprophytes, microorganisms growing on starch-ammonia agar (SAA), hydrocarbon-oxidizing bacteria (PSB), micromycetes and actinomycetes were estimated. The mineralization coefficient is calculated. The total number of microflora in the samples ranged from 51 to 271 million CFU/g. The share of saprophytes was 16.724.8% of the total amount of microflora. The proportion of microorganisms growing on SAA was 15.6-36.6%. The minimum number of PSB was 2.0 million CFU/g of soil; the maximum was 22.0 million CFU/g. The mineralization coefficient varies from 0.81 to 1.63, which indicates different rates of mineralization processes. The number of micromycetes determined on the Chapek medium ranged from 0.01 to 3.33 million CFU/g, on SAA from 0.03 to 10.4 million CFU/g. At the same time, the number of micromycetes is much lower than the number of bacteria, which is normal for soils. The number of actinomycetes varied from 0.2 to 7.3 million CFU/g. The largest number of actinomycetes was noted when peat and humic preparation Rostock were introduced. The share of actinomycetes in the total number of microflora on the SAA ranged from 0.6 to 14%. There is a development of the total number of microflora, an increase in the diversity of microbocenosis, which indicates a decrease in the concentrations of water-soluble salts, petroleum products and the presence of an additional food source in the form of peat. Based on the data obtained, a conclusion was made about the possibility of using soils based on drilling sludge with the addition of peat and humic preparation Rostock for the reclamation of disturbed lands.

БАКТЕРИИ-НЕФТЕДЕСТРУКТОРЫ С УСТОЙЧИВОСТЬЮ К ПРИСУТСТВИЮ ДОПОЛНИТЕЛЬНЫХ ПОЛЛЮТАНТОВ

Throughout the world, significant areas of agricultural land are polluted with hydrocarbons. Their microbiological purification is hampered by the presence of residual amounts of pesticides (herbicides, in particular), which inhibit the vital activity of oil-destructing bacteria. In addition, along with crude oil, heavy metals and salts (mainly chlorides) can enter arable soils, which, in turn, have a negative effect on microorganisms. Therefore, for the bioremediation of such territories, hydrocarbon-oxidizing bacteria resistant to the presence of additional pollutants should be used. In the present work, three isolates were identified that are capable of active growth in a liquid medium with oil. Using time-of-flight matrix-activated laser desorption-ionization (MALDI-TOF) mass spectrometry of the cellular protein fraction, sequencing of the nucleotide sequence of the 16S rRNA gene and phylogenetic analysis, the species of microorganisms belonging to the genus Acinetobacter was determined. The bacteria had a significant ability to biodegrade oil (71.8-74.1%), which was estimated from the degree of destruction of the aliphatic oil fraction by the gas chromatographic method after preliminary extraction with hexane. The resistance of microorganisms to the presence of herbicides, heavy metals, and sodium chloride was determined by their growth on meat-peptone agar with different concentrations of preparations, salts of these metals, or NaCl. The strains showed resistance to the presence in the medium of herbicides based on 2,4-D and imazethapyr at a concentration of 10.0 ml/l, sodium chloride in an amount of 5.0-6.0%, and lead ions (1.00-1.25 g/l). In addition, they produced lipase and were capable of fixing atmospheric nitrogen and dissolving inorganic phosphate. The last two properties are important for stimulating the growth and development of remedial plants. The obtained results indicate that all three strains have certain prospects of application for cleaning oil-contaminated agricultural soils and require further study of their biotechnological potential.

Promising Strains of Hydrocarbon-Oxidizing Pseudomonads with Herbicide Resistance and Plant Growth-Stimulating Properties for Bioremediation of Oil-Contaminated Agricultural Soils

Nowadays, large areas of agricultural land are contaminated with chemical plant-protection products. Agricultural soils are also susceptible to oil pollution as a result of accidents on oil pipelines. Bioremediation of such soils from oil with the help of hydrocarbon-oxidizing bacteria is hindered by the presence of additional pollutants such as herbicides. In this work, seven strains of Pseudomonas were isolated and identified, which showed differences in ability of oil biodegradation (32.7–77.3%). All strains showed resistance to herbicides based on 2,4-D and substances from the class of imidazolinones, possessed phosphate-solubilizing and nitrogen-fixing activity, and produced indolyl-3-acetic acid (305–1627 ng/mL culture liquid). They stimulated the growth of barley and clover in soil with oil, as well as the growth of clover in soil with herbicide. In a vegetative experiment (duration 30 days, initial oil content in soil 2% wt., herbicide based on imazethapyr 0.002% wt.) of barley plants and P. alcaligenes UOM 10 or P. frederiksbergensis UOM 11, oil degradation was 48.1–52.7%, the same strains and clover plants, 37.9–38.6%. The studied bacteria have the potential to be used in the bioremediation of oil-contaminated agricultural soils, including in combination with phytomeliorant plants.

Ways of Long-Term Survival of Hydrocarbon-Oxidizing Bacteria in a New Biocomposite Material-Silanol-Humate Gel.

Immobilized bacterial cells are presently widely used in the development of bacterial preparations for the bioremediation of contaminated environmental objects. Oil hydrocarbons are among the most abundant pollutants. We have previously described a new biocomposite material containing hydrocarbon-oxidizing bacteria (HOB) embedded in silanol-humate gels (SHG) based on humates and aminopropyltriethoxysilane (APTES); high viable cell titer was maintained in this material for at least 12 months. The goal of the work was to describe the ways of long-term HOB survival in SHG and the relevant morphotypes using the techniques of microbiology, instrumental analytical chemistry and biochemistry, and electron microscopy. Bacteria surviving in SHG were characterized by: (1) capacity for rapid reactivation (growth and hydrocarbon oxidation) in fresh medium; (2) ability to synthesize surface-active compounds, which was not observed in the cultures stored without SHG); (3) elevated stress resistance (ability to grow at high Cu2+ and NaCl concentrations); (4) physiological heterogeneity of the populations, which contained the stationary hypometabolic cells, cystlike anabiotic dormant forms (DF), and ultrasmall cells; (5) occurrence of piles in many cells, which were probably used to exchange genetic material; (6) modification of the phase variants spectrum in the population growing after long-term storage in SHG; and (7) oxidation of ethanol and acetate by HOB populations stored in SHG. The combination of the physiological and cytomorphological properties of the cells surviving in SHG for long periods may indicate a new type of long-term bacterial survival, i.e., in a hypometabolic state.

Structure and Seasonal Variability of Groundwater Microbial Communities in the City of Moscow

Abstract—Groundwater, which appears on the surface in the form of springs, is an important ecologically significant component of the aquatic ecosystem, sensitive to changes in environmental conditions. The anthropogenic impact associated with urbanization leads to a change in the characteristics of groundwater, which in turn affects the composition of microbial communities in spring waters. Using high-throughput sequencing of the 16S ribosomal RNA gene fragments, we characterized the composition of microbial communities in five natural springs in the city of Moscow in the spring, summer, and winter seasons. The microbial communities of each spring in different seasons were similar to each other and clearly differed from the microbiomes of other springs. Among the Archaea, which averaged about 20% of microbial communities, ammonium-oxidizing Crenarchaeota predominated, as well as Nanoarchaeota. Most of the Bacteria belonged to the phyla Proteobacteria, Patescibacteria, Verrucomicrobiota, Chloroflexi, and Bacteroidota. Autotrophic bacteria, including iron-oxidizing bacteria of the family Gallionellaceae and nitrifiers, as well as methanotrophs, accounted for significant proportions in microbial communities in the springs with a presumably deeper water source. Chemical and molecular analyzes did not reveal contamination of spring waters with toxic substances and oil-derived products, as well as the presence of pathogenic microorganisms and indicators of fecal pollution. However, during the spring season, the proportions of halophilic and hydrocarbon-oxidizing bacteria increased in water microbiomes, which may reflect entry into groundwater after snow thawing of deicin reagents and hydrocarbons, which are successfully biodegraded in the soil.

Biological Activity of Leached Chernozem under Oil and Sodium Chloride Pollution and the Effect of Treatment with Halotolerant Oil-Destructing Bacteria

Soil contamination with oil is often accompanied by pollution by oilfield wastewater, which contains a significant amount of NaCl, which enhances the negative impact of hydrocarbons on soil, plants, and soil microbiota. Therefore, for the biotechnological purification of soils subjected to such combined pollution, hydrocarbon-oxidizing bacteria resistant to salinity should be used. In a model experiment, the effect of artificial pollution with oil (5%) and sodium chloride (1 and 3%) and their combinations, as well as bioremediation using halotolerant hydrocarbon-oxidizing bacteria on the biological activity of leached chernozem (Luvic Chernozem) was studied. Soil contamination with all types of pollution increased its phytotoxicity, while bacterization did not have a positive effect on this indicator in the presence of NaCl and with combined pollution, but contributed to a decrease in toxicity for plants of oil-containing soil. The most sensitive to the presence of oil and/or NaCl were actinomycetes, the number of which decreased by 1–2 orders of magnitude. The introduction of microorganisms increased the decomposition of hydrocarbons, including in complex polluted soil by 10.5–31.8%. In general, the presence of pollutants reduced the activity of soil enzymes. Bacterization contributed to some increase in the level of catalase in soil with oil, restored urease activity in oil-containing soil and under the combined action of pollutants, and increased invertase activity under combined pollution.

МИКРОБИОЛОГИЧЕСКАЯ ХАРАКТЕРИСТИКА ГИДРОТЕХНИЧЕСКИХ СООРУЖЕНИЙ НЕКОТОРЫХ БУХТ Г. СЕВАСТОПОЛЯ

Hydraulic structures, which are constantly present in bays, are one of the factors affecting the condition of coastal waters. Microperiphyton, which is formed on hydraulic structures in coastal zones with varying degrees of anthropogenic and recreational pressure, has the greatest indicative value. Microbiological studies of periphyton significantly complement the characterization of the ecological state of the coast. This study presents data on the quantitative distribution of heterotrophic and hydrocarbon-oxidizing bacteria in the microperiphyton of silt deposits of the southern breakwater of Sevastopol Bay and the eastern breakwater of Kamyshovaya Bay. The total number of heterotrophic bacteria in the silt deposits of the southern breakwater generally ranged from 103 to 104 cells/ml, while that of the eastern breakwater mainly varied within 103–105 cells/ml. The results obtained indicate that the silty deposits in the considered water areas to the development of the analyzed groups of bacteria participating in the processes of self-purification of water areas, and their number does not depend on the depth. Data analysis showed that the number of heterotrophic bacteria in the eastern breakwater was higher than in the southern breakwater. Seasonal differences in the number of studied groups of bacteria were not revealed. It was found that the processes of self-purification of the marine environment from oil and petroleum products are more active on the outer side of the breakwater, and these processes are more pronounced on the southern breakwater.

Bioremediation potential of native microorganisms of the southern chernozem

In the course of the conducted studies, main groups of soil microorganisms in the southern chernozem were identified. The resistance of isolates to the action of oil in the concentration range of 15–25%, the possibility of using it as a carbon source, the ability of soil microbiota to biodegradate oil in contaminated soil and the resistance of bacteria to low temperatures, high NaCl concentrations, acid and alkali resistance were established. 15 genera (31 species) of heterotrophic bacteria were isolated from uncontaminated soil samples of the southern chernozem subtype. Our assessment of the abundance dynamics of microorganisms isolated from laboratory contaminated soils showed that as a result of oil exposure, there was a significant decrease in the numbers of microorganisms: by the 180th day of our experiment, 10 bacteria species belonging to 3 genera were isolated, namely: Bacillus, Micrococcus and Serratia. Among the isolated bacteria, resistance to the action of the pollutant at a concentration of 25% was established for B. coagulans, B. mojavensis, B. megaterium, M. luteus, as well as for the museum strain of B. pumilus CM. By cultivating the studied bacterial strains on a carbon-free medium M9 with 15 and 20% oil added, their ability to use petroleum hydrocarbons as the only carbon source was established; however, when the concentration increased to 25%, only M. luteus, B. mojavensis and B. pumilus KM retained this ability. The presence of hydrocarbon-oxidizing bacteria in soil samples contributed to the 42% decrease in the oil mass concentration in 180 days. The most significant decrease in the concentration of petroleum products occurred in the period from the 10th to the 30th day and amounted to 25%, which is probably due to the increase in the numbers of heterotrophic bacteria. The ability to grow at a temperature of +4°C was established for representatives of the genus Bacillus, including the museum strain of B. pumillus CM, 4 strains of bacilli remained viable in an acidic environment (pH 5), 7 strains of bacilli and M. luteus and S. plymuthica remained viable in an alkaline environment (pH 9). The studied bacterial strains were growing on a GRM-agar with a NaCl concentration of 7%, the ability to grow at a NaCl concentration of 15% was preserved only by the museum strain of B. pumillus KM. The obtained results open the prospects for the use of hydrocarbon-oxidizing bacteria with a high adaptive potential as potential oil destructors capable of biodegradation at low temperatures, in conditions of high salinity and in a wide range of pH of the medium.

The state of the intestinal bacterial community in mollusks for assessing habitat pollution in the gulf of Finland (Baltic Sea)

In this study, we investigated the abundance and diversity of bacteria in the digestive tract of the bivalve mollusks Unio pictorum after 30-day exposure in experimental cages and field-collected gastropod mollusk Radix balthica in the eastern Gulf of Finland, Baltic Sea. Contamination of water and sediments with petroleum hydrocarbons had a significant impact on the intestinal bacterial community of mollusks stimulating the growth of hydrocarbon-oxidizing bacteria. The abundance of the intestinal hydrocarbon-oxidizing bacteria correlated with the concentration of the total hydrocarbons in the water of the coastal sites in the Gulf, where the mollusks were exposed. Metagenomic analysis revealed significant differences in the intestinal microbial community composition between polluted and unpolluted sites. The increased abundance of members of the phylum Gammaproteobacteria, including species of Aeromonas, Acinetobacter, Arenimonas, Pseudomonas, Rheinheimera, and Shewanella, and Bacteroidetes (Flavobacterium and Pedobacter) in the intestinal tracts of mollusks Unio pictorum were found at hydrocarbon-contaminated site: therefore, these bacteria are key players in the adaptation of intestinal community to this kind of pollution and hydrocarbon degradation. Our study suggests that hydrocarbon-oxidizing bacteria have the potential as a sensitive bioindicator for the further monitoring and ecological assessment of marine ecosystems.