Petroleum Hydrocarbon-degrading Bacteria Research Articles

Naphthalene-Degrading Bacteria with Potential for Remediating Marine Environments

Brazil is one of the largest oil producers in the world, and petroleum exploration is predominant in marine environments, mainly in the city of Rio de Janeiro. These environments become vulnerable to oil spills, which can be remedied by petroleum hydrocarbon-degrading bacteria. To better understand the distribution of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria in these marine environments, water samples were collected from eight beaches (Arpoador, Grumari, Vermelha, Sahy, Itacuruçá, Itaipuaçu, Ferradura, and Itaipu) along the Rio de Janeiro coastline and further contaminated with 0.1% naphthalene, used as a PAH model. Naphthalene-enriched bacteria were isolated in marine agar, identified using 16S rRNA sequencing, and tested for emulsification and naphthalene degradation. Thirty-five different genera were observed among the 231 isolates, most belonging to Proteobacteria. Some genera were found in at least half of the studied beaches, such as Mesoflavibacter, Muricauda, Alteromonas, Salipiger, Pseudooceanicola, and Celeribacter, while others were found in only a few water samples. Seventeen and 18 strains were considered to be positive for naphthalene degradation and emulsification, respectively, making them the most promising strains for naphthalene bioremediation. Five of these strains were positive for both degradation and emulsification. This study contributes to the selection of potential candidates for further studies on the remediation of PAHs in tropical marine environments worldwide.

Inoculum of Pseudomonas sp. D_192 significantly alters the prokaryotic community in simulated liquid paraffin-contaminated seawater environment

The investigation involved the utilization of coastal water microcosms that simulated hydrocarbon pollution with liquid paraffin over a duration of 56 days. An inoculum of Pseudomonas sp. D_192 (P_D192), possessing oil degradability, was introduced into the microcosms to examine the impact of externally fortified bacteria within the background medium on the prokaryotic community during the treatment of hydrocarbon pollution in seawater. Significant disparities in alpha/beta diversity and prokaryotic community composition were observed between microcosms with and without the addition of P_D192 inoculum. The introduction of the P_D192 inoculum was found to expedite the degradation of hydrocarbon pollutants by enhancing the relative abundance of petroleum hydrocarbon-degrading bacteria (especially Alcanivorax sp.) and fortifying metabolic functions associated with xenobiotics biodegradation and hydrocarbon degradation metabolism. Furthermore, the co-occurrence network of the microcosm with P_D192 inoculum exhibited a higher number of positive correlations, indicating an augmentation of facilitative interactions under the influence of Pseudomonas sp. D_192 inoculum.

Construction of Shale Gas Oil-Based Drilling Cuttings Degrading Bacterial Consortium and Their Degradation Characteristics.

Oil-based drilling cuttings (OBDCs) contain petroleum hydrocarbons with complex compositions and high concentrations, which have highly carcinogenic, teratogenic, and mutagenic properties. In this study, three highly efficient petroleum hydrocarbon-degrading bacteria were screened from OBDCs of different shale gas wells in Chongqing, China, and identified as Rhodococcus sp. and Dietzia sp. Because of their ability to degrade hydrocarbons of various chain lengths, a new method was proposed for degrading petroleum hydrocarbons in shale gas OBDCs by combining different bacterial species. Results showed that the bacterial consortium, consisting of the three strains, exhibited the highest degradation rate for petroleum hydrocarbons, capable of degrading 74.38% of long-chain alkanes and 93.57% of short-chain alkanes, respectively. Moreover, the petroleum hydrocarbon degradation performance of the bacterial consortium in actual OBDCs could reach 90.60% in the optimal conditions, and the degradation kinetic process followed a first-order kinetic model. This study provides a certain technical reserve for the bioremediation of shale gas OBDCs.

Remediation of Petroleum-contaminated Soil by Highly Efficient Oil-degrading Bacteria and Analysis of Its Enhancement Mechanism

A 120-day in situ remediation of oil-contaminated soil was carried out by using highly efficient oil-degrading bacteria. The effects of bio-enhanced remediation and changes in soil physicochemical properties and enzyme activities were investigated. Combined with metagenomic sequencing and bioinformatics analysis, the strengthening mechanism was revealed. The results showed that compared with the blank control group (Ctrl), the degradation rate of total petroleum hydrocarbons in the bioremediation group (Exp-BT) was significantly increased, reaching 81.23%. During enhanced bioremediation by highly efficient oil-degrading bacteria, the pH of the soil was stable, the oxidation capacity of the system was improved, and the electrical conductivity was in the range suitable for agricultural activities. Lipase and dehydrogenase maintained high activity during repair. In addition, the analysis of the initial contaminated soil (B0), the highly efficient oil-degrading bacteria obtained from domestication (GZ), and the soil samples after bioremediation (BT) in the obtained samples showed that, at the phylum level, the total proportion of Proteobacteria and Actinobacteria increased by 17.1%. At the genus level, the abundance of Nocardioides, Achromobacter, Gordonia, and Rhodococcus increased significantly. The species and function contribution analysis of COG and KEGG proved that the above bacterial genera had important contributions to the degradation of petroleum hydrocarbons. A high abundance of petroleum hydrocarbon-related metabolic enzymes and five petroleum hydrocarbon-related degradation genes was found in the soil after remediation:alkM, tamA, rubB, ladA, and alkB. The analysis showed that the introduction of the exogenous petroleum hydrocarbon-degrading bacteria group enhanced the metabolic activity of microorganism-related enzymes and the expression of corresponding functional genes.

Remediation of petroleum hydrocarbon-contaminated groundwater by biochar-based immobilized bacteria

It is essential to research the technology for effective remediation of petroleum hydrocarbon-contaminated groundwater because the petroleum hydrocarbon contamination of groundwater is becoming more and more serious. The petroleum hydrocarbon-degrading bacteria screened in this experiment were identified as Pseudomonas spp. by 16 S rDNA sequencing. Using wheat straw biochar as the carrier, a highly stable immobilized bacteria integrating adsorption and degradation was prepared by microbial immobilization technology. The results of scanning electron microscopy and Fourier transform infrared spectroscopy analysis showed that the microorganisms were adsorbed on the biochar. Degradation of petroleum hydrocarbon by immobilized bacteria conformed to the second-order kinetic model. For the manufacture of immobilized bacteria, the following immobilization parameters worked best: immobilization pH of 7 and immobilization time of 24 h. Finally, the produced immobilized bacteria were added to four groundwater samples with various initial concentrations of petroleum hydrocarbon, and it was found that all of the petroleum hydrocarbon degradations were above 95%. The study can serve as a useful resource for groundwater petroleum hydrocarbon remediation technology since the immobilized bacteria can successfully adapt to the groundwater petroleum hydrocarbon environment and significantly reduce the concentration of petroleum hydrocarbon.

Bioremediation of petroleum hydrocarbon contaminated soil by microorganisms immobilized on sludge modified by non-ionic surfactant.

The immobilization of microorganisms on high-quality and inexpensive carriers to remediate oil-contaminated soil is an effective strategy for contaminated soil remediation. Due to the abundance in nutrients, large specific surface area, and fewer pathogens, the composting sludge is considered a high-quality immobilized material. Herein, two non-ionic surfactants, TW-80 and sophorolipid, were used to modify composted sludge. High-efficiency petroleum hydrocarbon-degrading bacteria groups selected in the laboratory were fixed on the modified composting sludge under optimal conditions. The immobilized material was placed in the soil contaminated by petroleum hydrocarbons at an additive amount of 2wt/%, and a simulated remediation experiment was performed for 90days. Both soil properties and microbial structure were characterized. Surfactant-modified compost sludge enhances the adsorption capacity to petroleum hydrocarbon. The immobilized microorganisms in the modified compost sludge showed a good effect on the remediation of soil contaminated by petroleum hydrocarbons. In addition, immobilized materials also increase the diversity of the microbial community structure in the soil. High-efficiency petroleum hydrocarbon-degrading bacteria immobilized on surfactant-modified compost can effectively promote the degradation of petroleum hydrocarbons in the soil and increase the abundance of microorganisms in the soil. It shows the feasibility of eco-friendly remediation of hydrocarbon-contaminated soil.

New Technique for Enhancing Residual Oil Recovery from Low-Permeability Reservoirs: The Cooperation of Petroleum Hydrocarbon-Degrading Bacteria and SiO2 Nanoparticles.

Residual crude oil production from low-permeability reservoirs has become a huge challenge because conventional recovery techniques are inefficient. Nanofluids as a new type of oil-displacement agent have become a hot topic in recent years to enhance oil recovery (EOR) in reservoirs. However, the imperfection of agglomeration, dissolution, and instability of nanofluids in reservoir environments limit their ability to drive oil. Here, a novel "microbial-nanofluid" composed of petroleum hydrocarbon-degrading bacteria (PHDB, namely Bacillus cereus) and SiO2 nanoparticles was proposed as a potential new technology for enhancing residual oil recovery. The micromodel displacement test results showed that the optimum composite concentration of "microbial-nanofluids" were PHDB (7.0%, v/v) and SiO2 nanoparticles (100 mg/L), and the residual oil recovery was increased by 30.1% compared with waterflooding (68.8%). Moreover, the morphological characteristics of residual oil mobilization after "microbial-nanofluid" flooding were mainly small and dispersed oil droplets in the excessive areas, and the dead-end areas were almost clean with mobilization. Furthermore, the cooperation mechanism of four kinds of "microbial-nanofluids" to enhance the residual oil recovery in low-permeability reservoirs was preliminarily clarified, namely the co-emulsification of oil, working together to unclog oil clog, microbial-nanofluid self-assembly, and structural disjoining pressure. This study demonstrated that PHDB-SiO2 nanoparticle composite flooding technology provided a significant potential for the EOR from low-permeability reservoirs.

Complete Genome Sequences of One Salt-Tolerant and Petroleum Hydrocarbon-Emulsifying Terribacillus saccharophilus Strain ZY-1.

Salt tolerance is one of the most important problems in the field of environmental governance and restoration. Among the various sources of factors, except temperature, salinity is a key factor that interrupts bacterial growth significantly. In this regard, constant efforts are made for the development of salt-tolerant strains, but few strains with salt tolerance, such as Terribacillus saccharophilus, were found, and there are still few relevant reports about their salt tolerance from complete genomic analysis. Furthermore, with the development of the economy, environmental pollution caused by oil exploitation has attracted much attention, so it is crucial to find the bacteria from T. saccharophilus which could degrade petroleum hydrocarbon even under high-salt conditions. Herein, one T. saccharophilus strain named ZY-1 with salt tolerance was isolated by increasing the salinity on LB medium step by step with reservoir water as the bacterial source. Its complete genome was sequenced, which was the first report of the complete genome for T. saccharophilus species with petroleum hydrocarbon degradation and emulsifying properties. In addition, its genome sequences were compared with the other five strains that are from the same genus level. The results indicated that there really exist some differences among them. In addition, some characteristics were studied. The salt-tolerant strain ZY-1 developed in this study and its emulsification and degradation performance of petroleum hydrocarbons were studied, which is expected to widely broaden the research scope of petroleum hydrocarbon-degrading bacteria in the oil field environment even in the extreme environment. The experiments verified that ZY-1 could significantly grow not only in the salt field but also in the oil field environment. It also demonstrated that the developed salt-tolerant strain can be applied in the petroleum hydrocarbon pollution field for bioremediation. In addition, we expect that the identified variants which occurred specifically in the high-salt strain will enhance the molecular biological understanding and be broadly applied to the biological engineering field.

Presence of Hydrocarbon Degrading Bacteria in Contaminated Soil Collected From Various Fuel Station in Bhilai, Chhattisgarh

Abstract: In this study, we isolated seven strains (termed BY1–7) from polluted soil at an oil station and evaluated their abilities to degrade total petroleum hydrocarbons (TPHs). Among 45 bacterial colonies one bacterial strain was identified based on the cultural, morphological and biochemical characteristics. The isolated bacterium was then subjected to a preliminary assessment of their crude oil after 48 hours of incubation on nutrient agar plates overlaid with 100 ML of petroleum crude oil, the zone of clearance was observed. The isolated bacteria showed 35% petrol degradation, whereas a relatively high oil degradation rate, almost 40% was observed when the bacterium was acclimatized. The selected bacterial strains crude oil resistance was analysed based on the growth ability on the crude oil containing mediums. This strain was identified as Brevibacterium brevis. After inoculation, growth ability was measured and the highest percentage of petrol degradation occurred at temperature 37 °C with the value 30.8%. Bacteria displaying such capabilities are often exploited for the bio-remediation of petroleum oil contaminated environments. Recently, microbial remediation technology has developed rapidly and achieved major gains. However, this technology is not omnipotent. It is affected by many environmental factors that hinder its practical application, limiting the large-scale application of the technology. Keywords: Petroleum hydrocarbon-degrading Bacteria, Petroleum oil, Bio-remediation, Bacterial consortia, Environmental factors, Enzymes.

Evaluating the bio-removal of crude oil by vetiver grass (Vetiveria zizanioides L.) in interaction with bacterial consortium exposed to contaminated artificial soils

Remediation of crude oil-impacted areas is a major pervasive concern in various environmental conditions. The major aim of this study was to investigate the collaboration of vetiver grass (Vetiveria zizanioides L.) and petroleum hydrocarbon-degrading bacteria to clean up contaminated soils. Vetiver grass and five native bacterial isolates were used in one consortium to remediate contaminated soil by crude oil at various concentrations (2.0, 4.0, 6.0 8.0, 10, and 12.0% woil/wsoil). The presence of isolated bacteria caused a significant (p < 0.05) increment of root-shoot ratio of vetiver in contaminated soils in comparison to non-contaminated soil. The combination of vetiver and bacterial consortium revealed efficient dissipation of more than 30% of low-molecular-weight polycyclic aromatic hydrocarbons (PAHs) and more than 50% of high-molecular-weight PAHs in all crude oil concentrations. The removal of n-alkanes in the simultaneous presence of the bacteria and plant was more than 70.0% at 10.0% of oil concentration, whereas the removals in control were 20.7, 13.7 and 9.2%, respectively. The hydrocarbons dissipation efficiency of applied treatments decreased at 12.0% of contamination. It is concluded that a combination of vetiver grass and the isolated bacteria could be a feasible strategy for remediation of crude oil-polluted soils. Novelty statement Determination of the responses of vetiver grass under different crude oil concentrations is one of the novelties of the present study, which is helpful for demonstrating plant tolerance on polluted environments. Also, it adds information about the potential of this grass to clean up crude oil-polluted soils solely as well as in the presence of promising selected bacterial strains.

Oil Degrading Bacteria: Remediation of Environmental Pollution Resulting from Petroleum Hydrocarbons

It is widely known that petroleum hydrocarbons constitute one of the most hazardous pollutants that affect human and environmental health. The ongoing research on bioremediation with petroleum hydrocarbon-degrading bacteria has shown tremendous promise of the technology due to its advantages of high efficiency and eco-friendly nature. To this end, studies have been carried out to identify a large amount of bacterial species with petroleum hydrocarbon-degrading ability for applications in bioremediation. Here, we present a brief perspective of some of the notable advances in oil degrading bacteria and the remedial actions for decontamination of water and soil along with recovering the spilled materials at oil sites.

Directional culture of petroleum hydrocarbon degrading bacteria for enhancing crude oil recovery

An oxygen-constrained system of crude oil reservoir environment was constructed to stimulate the growth of indigenous microbes, such as petroleum hydrocarbon-degrading bacteria. Addition of nitrogen and phosphorus sources was investigated for the growth of petroleum hydrocarbon-degrading bacteria. The results show that nitrates and phosphates stimulated the growth of the bacteria and promoted the biodegradation of crude oil as the sole carbon source in this process. The minimum surface tension was 29.63 mN/m when the amounts of the nitrogen (NaNO3: NH42SO4 = 2:1) and phosphorus (KH2PO4: NaH2PO4 = 5:2) sources added were 0.8 wt% and 1.4 wt%, respectively. Furthermore, the dominant petroleum hydrocarbon-degrading bacteria were shifted from Arcobacter in production water to Pseudomonas after the first subculture and then to Bacillus after the sixth subculture. The heteroatom groups in the crude oil were biodegraded simultaneously with normal alkanes and alkyl cyclohexanes. Addition of the nutrients resulted in microbial growth, microbial community shift, and enhanced microbial degradation.

Degradation potential of petroleum hydrocarbon-degrading bacteria immobilized on different carriers in marine environment

Immobilization technology is a method for restoring the ecological environment of oil-polluted areas. In this paper, the performance and degradation characteristics of immobilized microorganisms on different carriers were systematically studied starting with the selection of immobilized carriers. The results showed that cinnamon shell was the best carrier for screened Pseudomonas YT-11 to prepare immobilized microorganisms (diesel degradation rate was 69.57% in 5 days). On the basis of the determination of diesel degradability and SEM structure, the degradation mechanism of immobilized microspheres was concluded: diesel was adsorbed on the surface of microspheres and then entered the interior to be degraded by microorganisms.

Petroleum Hydrocarbon-Degrading Bacteria for the Remediation of Oil Pollution Under Aerobic Conditions: A Perspective Analysis.

With the sharp increase in population and modernization of society, environmental pollution resulting from petroleum hydrocarbons has increased, resulting in an urgent need for remediation. Petroleum hydrocarbon-degrading bacteria are ubiquitous in nature and can utilize these compounds as sources of carbon and energy. Bacteria displaying such capabilities are often exploited for the bioremediation of petroleum oil-contaminated environments. Recently, microbial remediation technology has developed rapidly and achieved major gains. However, this technology is not omnipotent. It is affected by many environmental factors that hinder its practical application, limiting the large-scale application of the technology. This paper provides an overview of the recent literature referring to the usage of bacteria as biodegraders, discusses barriers regarding the implementation of this microbial technology, and provides suggestions for further developments.

Impact of nanoparticles on transcriptional regulation of catabolic genes of petroleum hydrocarbon-degrading bacteria in contaminated soil microcosms.

This study was conducted to determine what effects nanoparticles (NPs) like TiO2 , ZnO, and Ag may pose on natural attenuation processes of petroleum hydrocarbons in contaminated soils. The solid NPs used were identified using x-ray diffraction technique and their average size was certified as 18.2, 16.9, and 18.3 nm for Ag-NPs, ZnO-NPs, and TiO2 -NPs, respectively. NPs in soil microcosms behave differently where it was dissolved as in case of Ag-NPs, partially dissolved as in ZnO-NPs or changed into other crystalline phase as in TiO2 -NPs. In this investigation, catabolic gene encoding catechol 2,3 dioxygenase (C23DO) was selected specifically as biomarker for monitoring hydrocarbon biodegradation potential by measuring its transcripts by RT-qPCR. TiO2 -NPs amended microcosms showed almost no change in C23DO expression profile or bacterial community which were dominated by Bacillus sp., Mycobacterium sp., Microbacterium sp., Clostridium sp., beside uncultured bacteria, including uncultured proteobacteria, Thauera sp. and Clostridia. XRD pattern suggested that TiO2 -NPs in microcosms were changed into other non-inhibitory crystalline phase, consequently, showing the maximum degradation profile for most low molecular weight oil fractions and partially for the high molecular weight ones. Increasing ZnO-NPs concentration in microcosms resulted in a reduction in the expression of C23DO with a concomitant slight deteriorative effect on bacterial populations ending up with elimination of Clostridium sp., Thauera sp., and uncultured proteobacteria. The oil-degradation efficiency was reduced compared to TiO2 -NPs amended microcosms. In microcosms, Ag-NPs were not detected in the crystalline form but were available in the ionic form that inhibited most bacterial populations and resulted in a limited degradation profile of oil, specifically the low molecular weight fractions. Ag-NPs amended microcosms showed a significant reduction (80%) in C23DO gene expression and a detrimental effect on bacterial populations including key players like Mycobacterium sp., Microbacterium sp., and Thauera sp. involved in the biodegradation of petroleum hydrocarbons.

Long-term biodegradation of aged saline-alkali oily sludge with the addition of bulking agents and microbial agents.

Huge amount of aged oily sludge was generated during the drilling and transportation of crude oil. Sometimes, the sludge exhibited characters of combined pollution, such as saline-alkali oily sludge. Orthogonal experiments of L16(45) were conducted to evaluate the long-term effects of total petroleum hydrocarbons (TPH) concentration, microbial agents (Oil Gator and ZL) and bulking agents (peat and wheat bran) on the biodegradation of aged saline-alkali oily sludge. Compared with the control group, the significant improvement in the removal rate of TPH was exhibited with the addition of microbial agents and bulking agents after 231 days of the experimental period. Based on the values of mean range (R), it was revealed that the predominant influencing factor of the bioremediation was TPH concentration. After biostimulation and bioaugmentation, the quantity of petroleum hydrocarbon-degrading bacteria in the oily sludge increased by 2–4 orders of magnitude. Furthermore, the bioremediation improved the microbial diversity based on the analysis of PCR-DGGE. It was inferred that the addition of microbial agents and bulking agents reconstructed the microbial ecological niche. The principal component analysis indicated that the differentiation of the microbial community was generated by the biostimulation and bioaugmentation in comparison with the control samples.

Flavobacterium naphthae sp. nov., isolated from oil-contaminated soil.

During a study of petroleum hydrocarbon-degrading bacteria, a yellow-coloured, Gram-stain-negative, non-motile and rod-shaped bacterium, designated strain Brt-MT, was isolated from oil-contaminated soil of Biratnagar, Morang, Nepal. Strain Brt-MT was able to grow at 15-45 °C, pH 5.0-9.0 and 0-1 % (w/v) NaCl concentration. The strain was characterized by multiple taxonomic approaches. Based on 16S rRNA gene sequence analysis, strain Brt-MT belonged to the genus Flavobacterium and shared highest sequence similarity with Flavobacterium cloacae wh15T (95.69 %) and Flavobacterium anatoliense MK3T (94.91 %). The only respiratory quinone was MK-6; the major polar lipid was phosphatidylethanolamine; and the predominant fatty acids were iso-C15 : 0, summed feature 9 (iso-C17 : 1ω9c and/or C16 : 010-methyl), iso-C17 : 0 3-OH and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The DNA G+C content was 37.2 mol%. The morphological, physiological, chemotaxonomic and phylogenetic analyses clearly distinguished this strain from its closest phylogenetic neighbours. Thus, strain Brt-MT represents a novel species of the genus Flavobacterium, for which the name Flavobacteriumnaphthae sp. nov. is proposed. The type strain is Brt-MT (=KEMB 9005-692T=KACC 19393T=JCM 32171T).

Isolation of Petroleum Hydrocarbon Degrading Bacteria from the Liaohe Estuary at Cold Climate

Two cold-tolerant petroleum hydrocarbon degrading bacteria strain named CHD1 and CHD2 were isolated from oil-contaminated soil at cold climate. The isolated strains were able use diesel oil as sole carbon. The petroleum hydrocarbon degradation rate was analyzed using UV-spectrometry-based methods. The results showed that the diesel oil degradation rate of CHD1 and CHD2 were 22% and 25%, respectively.

Isolation and Characterization of Petroleum Hydrocarbon Degrading Bacteria from the Bohai Sea, China

Fourteen petroleum hydrocarbon degrading bacteria strains were isolated from oil-contaminated site. Isolated strains were able use diesel oil as sole carbon and energy source. Bacterial strain HD1 was selected due to the luxuriant growth on oil agar. The oil degradation rate of strain HD1 was analyzed using UV-spectrometry-based methods. The result showed that the rate of diesel oil degradation of 75% was observed after 14days of cultivation.

Aquatic Organisms and Petroleum Hydrocarbon Degrading Bacteria Associated with Their Digestive System

Laboratory investigation was carried out on the abundance and composition of bacteria in the digestive system of a total of 35 specimens, including bivalve molluscs, i.e. swan mussel Anodonta cygnea (Linnaeus, 1758) from Lake Spėra (Sirvintos district) and swollen river mussel Unio tumidus (Philipson, 1788) from the Curonian Lagoon near Juodkrantė, zebra mussel ( Dreissena polymorpha ) from the Curonian Lagoon near Juodkrantė and an anostracan – Chirocephalus josephinae (Grube, 1853) from a pond in Ilciukai village, Utena district, and in the water of related water bodies. Studies on bivalve molluscs (swan mussel and swollen river mussel), zebra mussel and an anostracan – Chirocephalus josephinae , as well as microbiological investigation of water demonstrated that the number of microorganisms in the digestive system of mollusc and anostracan species fluctuated and varied between different species and water bodies. The greatest percentage of HDB among total heterotrophic bacteria was found in the digestive system of swollen river mussels (21.53%) and in zebra mussels (19.99%) caught in the Curonian Lagoon and in the water of the lagoon (24%). A considerably smaller percentage of HDB was detected in the digestive system of swan mussels from Lake Spėra (17.6%) and in the water of the lake (16.66%). The smallest percentage of HDB was found in the digestive system of Chirocephalus josephinae (6.63%) and in the water of the Ilciukai pond (2.72%). According to the values of abundance of petroleum hydrocarbon-degrading bacteria (HDB) and total coliform bacteria (TCFB) in the digestive system of aquatic organisms we can state that the water ecosystem of Ilciukai pond was the least contaminated with petroleum, its products and sewage water, and the Curonian Lagoon water ecosystem was the most contaminated. Abundance of petroleum hydrocarbons degrading bacteria could be used as a bioindicator reflecting the level of ecosystem pollution petroleum and its products. DOI: http://dx.doi.org/10.5755/j01.erem.66.4.5300