Concentrations Of Crude Oil Research Articles

Stimulation of diesel degradation and biosurfactant production by aminoglycosides in a novel oil-degrading bacterium Pseudomonas luteola PRO23

Bioremediation is promising technology for dealing with oil hydrocarbons contamination. In this research growth kinetics and oil biodegradation efficiency of Pseudomonas luteola PRO23, isolated from crude oil-contaminated soil samples, were investigated under different concentrations (5, 10 and 20 g/L) of light and heavy crude oil. More efficient biodegradation and more rapid adaptation and cell growth were obtained in conditions with light oil. The 5 to 10 g/L upgrade of light oil concentration stimulated the microbial growth and the biodegradation efficiency. Further upgrade of light oil concentration and the upgrade of heavy oil concentration both inhibited the microbial growth, as well as biodegradation process. Aminoglycosides stimulated biosurfactant production in P. luteola in the range of sub-inhibitory concentrations (0.3125, 0.625 ?g/mL). Aminoglycosides also induced biofilm formation. The production of biosurfactants was the most intense during lag phase and continues until stationary phase. Aminoglycosides also induced changes in P. luteola growth kinetics. In the presence of aminoglycosides this strain degraded 82% of diesel for 96 h. These results indicated that Pseudomonas luteola PRO23 potentially can be used in bioremediation of crude oil-contaminated environments and that aminoglycosides could stimulate this process.

The effect of dispersed Petrobaltic oil droplet size on photosynthetically active radiation in marine environment.

Oil pollution in seawater, primarily visible on sea surface, becomes dispersed as an effect of wave mixing as well as chemical dispersant treatment, and forms spherical oil droplets. In this study, we examined the influence of oil droplet size of highly dispersed Petrobaltic crude on the underwater visible light flux and the inherent optical properties (IOPs) of seawater, including absorption, scattering, backscattering and attenuation coefficients. On the basis of measured data and Mie theory, we calculated the IOPs of dispersed Petrobaltic crude oil in constant concentration, but different log-normal size distributions. We also performed a radiative transfer analysis, in order to evaluate the influence on the downwelling irradiance Ed, remote sensing reflectance Rrs and diffuse reflectance R, using in situ data from the Baltic Sea. We found that during dispersion, there occurs a boundary size distribution characterized by a peak diameter d0 = 0.3 μm causing a maximum E d increase of 40% within 0.5-m depth, and the maximum Ed decrease of 100% at depths below 5 m. Moreover, we showed that the impact of size distribution on the "blue to green" ratios of Rrs and R varies from 24% increase to 27% decrease at the same crude oil concentration.

How much crude oil can zooplankton ingest? Estimating the quantity of dispersed crude oil defecated by planktonic copepods

We investigated and quantified defecation rates of crude oil by 3 species of marine planktonic copepods (Temora turbinata, Acartia tonsa, and Parvocalanus crassirostris) and a natural copepod assemblage after exposure to mechanically or chemically dispersed crude oil. Between 88 and 100% of the analyzed fecal pellets from three species of copepods and a natural copepod assemblage exposed for 48 h to physically or chemically dispersed light crude oil contained crude oil droplets. Crude oil droplets inside fecal pellets were smaller (median diameter: 2.4–3.5 μm) than droplets in the physically and chemically dispersed oil emulsions (median diameter: 6.6 and 8.0 μm, respectively). This suggests that copepods can reject large crude oil droplets or that crude oil droplets are broken into smaller oil droplets before or during ingestion. Depending on the species and experimental treatments, crude oil defecation rates ranged from 5.3 to 245 ng-oil copepod−1 d−1, which represent a mean weight-specific defecation rate of 0.026 μg-oil μg-Ccopepod1 d−1. Considering a dispersed crude oil concentration commonly found in the water column after oil spills (1 μl L−1) and copepod abundances in high productive coastal areas, copepods may defecate ∼1.3–2.6 mg-oil m−3 d−1, which would represent ∼0.15%–0.30% of the total dispersed oil per day. Our results indicate that ingestion and subsequent defecation of crude oil by planktonic copepods has a small influence on the overall mass of oil spills in the short term, but may be quantitatively important in the flux of oil from surface water to sediments and in the transfer of low-solubility, toxic petroleum hydrocarbons into food webs after crude oil spills in the sea.

Enrichment and isolation of crude oil degrading bacteria from some mussels collected from the Persian Gulf

To date, little is known about existing relationships between mussels and bacteria in hydrocarbon-contaminated marine environments. The aim of this study is to find crude oil degrading bacteria in some mussels at the Persian Gulf. Twenty eight crude oil degrading bacteria were isolated from three mussels species collected from oil contaminated area at Persian Gulf. According to high growth and degradation of crude oil four strains were selected between 28 isolated strains for more study. Determination the nucleotide sequence of the gene encoding for 16S rRNA show that these isolated strains belong to: Shewanella algae isolate BHA1, Micrococcus luteus isolate BHA7, Pseudoalteromonas sp. isolate BHA8 and Shewanella haliotis isolate BHA35. The residual crude oil in culture medium was analysis by Gas Chromatography (GC). The results confirmed that these strains can degrade: 47.24%, 66.08%, 27.13% and 69.17% of crude oil respectively. These strains had high emulsification activity and biosurfactant production. Also, the effects of some factors on crude oil degradation by isolated strains were studied. The results show that the optimum concentration of crude oil was 2.5% and the best degradation take place at 12% of salinity. This research is the first reports on characterization of crude oil degrading bacteria from mussels at Persian Gulf and by using of these bacteria in the field the effect of oil pollution can be reduce on this marine environment.

English

The influence of rhizobacteria on the growth and tolerance of Zea mays (maize) in a petroleum hydrocarbon (crude oil) impacted medium was investigated. This study evaluated the effect of inoculating maize seeds with plant growth promoting rhizobacterial strains in a crude oil impacted medium. The rhizobacterial strains used in this study were tested for plant growth promoting traits [indole-3-acetic acid production, siderophore production, phosphate solubilisation and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity] following standard methods and plant root and shoot elongation activity of these strains were assayed using modified root elongation assay. The isolates were identified as Bacillus circulans, Enterobacter intermedius and Staphylococcus carnosus, by analytical profile index (API). The results showed that seeds inoculated with plant growth promoting rhizobacteria (PGPR) exhibited significant vegetative growth at various petroleum crude oil concentrations (1, 2 and 4 ml) compared with uninoculated seeds. The root and shoot length of inoculated seeds were 10.2 and 4.3 cm (B. circulans), 7.2 and 1.7 cm (E. intermedius), 5.2 and 3.8 cm (S. carnosus) and 0.9 and 1.5 cm (uninoculated), all at 1 ml concentration of petroleum crude oil. Tolerance Index (TI) for PGPR inoculated maize seeds in the crude oil impacted medium was highest with B. circulans (2.08 to 1.92), S. carnosus (0.69 to 0.59) and E. intermedius (0.79 to 0.71). Thus, this study suggests that B. circulans could be employed as a crude oil tolerant rhizobacterium (PGPR) for mitigating the toxic effects of crude oil on plants and subsequently enhancing the plant growth in a crude oil-impacted soil. Key words: Plant growth-promoting rhizobacteria, tolerance index, crude-oil, impacted medium, growth parameters.

Cold-adapted bacteria for bioremediation of crude oil-contaminated soil

BACKGROUND There are many cold climate terrestrial sites contaminated with petroleum hydrocarbons. Successful bioremediation in these regions relies heavily on suitable microorganisms with biodegrading capability at low temperatures. This work aims at screening cold-adapted bacteria strains and examining their capability of biodegrading petroleum contaminants. RESULTS Eleven strains of cold-adapted bacteria were isolated from oily sludge taken from a cold environment. Three strains, identified as Chryseobacterium, Bacillus and Pseudomonas, respectively, demonstrated high efficiency in biodegradation of crude oil pollutants based on the growth curves and oil removal rate. The optimal degradation conditions of the three bacteria were 10 °C, pH 7 and salinity of 10 g L−1 for a crude oil concentration at 1000 mg L−1. Under these conditions, the oil removal of the three bacteria after 8 days was 62.3, 61.6 and 60.9%, respectively. The strains were applied in simulated bioremediation tests using artificial contaminated soil containing 5.8–10.6 g oil kg−1 soil and achieved 61–78% oil removal after 150 days of bioremediation at 10 °C. CONCLUSION The three cold-adapted bacteria strains are capable of degrading crude oil efficiently at low temperatures and thus are suitable for bioremediation of petroleum contaminated soils in cold environments. © 2015 Society of Chemical Industry

Application of deep eutectic solvents and their individual constituents as surfactants for enhanced oil recovery

Abstract We investigated the potential use of choline chloride/urea and choline chloride/glycerol deep eutectic solvents (DESs) and their individual constituents (the salt and the hydrogen bond donor) as surfactants for enhanced oil recovery. The interfacial tension (IFT) between Saudi medium crude oil and different concentrations of these DESs (and their individual components) in 10 wt% NaCl aqueous solutions were measured as a function of temperature. Results showed that the IFT values decreased with the increase of both the DES concentration and temperature. The effect of adding the salt and the hydrogen bond donor (HBD) separately, without forming the corresponding DES, on IFT values was also explored. It was found that, in most cases, adding the DES or its corresponding constituents separately has the same effect on the IFT. Furthermore, 1 H NMR and different 2D NMR analysis (NOESY and HOESY) were used to examine the nature of molecular interactions that occur in studied DESs and how water affects these interactions. It was found that while the content of water is below 25 wt% the interactions of DES’ components become weak. However, the addition of 50 wt% water breaks the hydrogen bonding so that no interactions between the HBD and the salt were observed.

Sequential Preconditioning and Its Effect on Crude Oil Bioremediation by Indigenous Soil Bacteria

Preconditioning has been proved to result in a significant increase in adaptability of biological organisms to adverse environmental stimulations and various stressful conditions. Accordingly, in a new approach attempt was made to enhance hydrocarbon degradation ability of selected potential isolates from a petroleum polluted soil through sequential adaptation. Firstly 8 isolates selected based on their growth at 5% (v/v) crude oil. Second selection performed based on their ability to adapt gradually them to 10%, 20% and 50% (v/v) crude oil concentration respectively, at simulated natural conditions (6.5 pH, 32°C). Isolates transferred to higher concentration of crude oil every 14 days. Their exponential growth rate served as an indicator of their adaptation success. Selected bacteria identified biochemically and morphologically according to Bergey's manual accompanied by 16s rRNA sequencing. Bacterial species were identified as P. putida, A. lwoffi, A. hydrophila, P. stutzeri, and A. johnsonii. Bacterial isolates were tested for their biodegradation ability individually and as a consortium; based on gas chromatographic analysis the consortium proved to be more efficient in n-alkane degradation as 93% of C8-C33 was removed in liquid cultures and 70% of hydrocarbons in artificially polluted soils, in 28 days. In addition ratios of n17/ pristane and n18/ phytane degradation supported the promising bioremediation ability of the consortium. Comparison between adapted and un-adapted bacteria revealed that aliphatic degradation enhanced up to 40% in soil. In general the results suggest that preconditioning bacterial isolates to higher oil concentration can significantly enhance their biodegradation ability especially as a consortium.

Enhanced bioremediation of crude oil in polluted beach sand by the combination of bioaugmentation and biodiesel

Biodiesel produced from rapeseed oil was used as a cost-effective and sustainable agent to enhance crude oil biodegradation in sand microcosms. The initial concentration of crude oil and total petroleum hydrocarbon (TPH) was 20,000 and 18,750 mg/kg, respectively. The mass ratio of biodiesel to crude oil was 0 (designated T1), 1:10 (designated T2), 1:4 (designated T3), and 1:2 (designated T4). After 80 days of incubation, the total removals of TPH and PAHs were 68.6 and 61.5% in T1, 78.0 and 67.3% in T2, 86.3 and 76.2% in T3, 72.2 and 57.9% in T4, respectively. Higher amounts of biodiesel reduced TPH biodegradation due to the decreased transfer of substrates caused by dilution effect. The addition of biodiesel stimulated bacterial growth during the initial period but the petroleum hydrocarbon degradation is not always correlated with the density of bacteria in the presence of biodiesel. Dehydrogenase activity (DHA) and polyphenol oxidase (PPO) activity increased greatly after the beginning of incubation. From then on, DHA continuously decreased with time. T3 had the highest DHA and PPO activity from day 30 to the end of the experiment. The lowest toxicity was observed in T3 at day 80, and T3 showed the highest degradation rate constant.

Multiwall carbon nanotubes increase the microbial community in crude oil contaminated fresh water sediments

Since crude oil contamination is one of the biggest environmental concerns, its removal from contaminated sites is of interest for both researchers and industries. In situ bioremediation is a promising technique for decreasing or even eliminating crude oil and hydrocarbon contamination. However, since these compounds are potentially toxic for many microorganisms, high loads of contamination can inhibit the microbial community and therefore reduce the removal rate. Therefore, any strategy with the ability to increase the microbial population in such circumstances can be of promise in improving the remediation process. In this study, multiwall carbon nanotubes were employed to support microbial growth in sediments contaminated with crude oil. Following spiking of fresh water sediments with different concentrations of crude oil alone and in a mixture with carbon nanotubes for 30days, the microbial profiles in these sediments were obtained using FLX-pyrosequencing. Next, the ratios of each member of the microbial population in these sediments were compared with those values in the untreated control sediment. This study showed that combination of crude oil and carbon nanotubes can increase the diversity of the total microbial population. Furthermore, these treatments could increase the ratios of several microorganisms that are known to be effective in the degradation of hydrocarbons.

Induction of reactive oxygen species in marine phytoplankton under crude oil exposure.

Exposure of phytoplankton to the water-accommodated fraction of crude oil can elicit a number of stress responses, but the mechanisms that drive these responses are unclear. South Louisiana crude oil was selected to investigate its effects on population growth, chlorophyll a (Chl a) content, antioxidative defense, and lipid peroxidation, for the marine diatom, Ditylum brightwellii, and the dinoflagellate, Heterocapsa triquetra, in laboratory-based microcosm experiments. The transcript levels of several possible stress-responsive genes in D. brightwellii were also measured. The microalgae were exposed to crude oil for up to 96 h, and Chl a content, superoxide dismutase (SOD), the glutathione pool (GSH and GSSG), and lipid peroxidation content were analyzed. The cell growth of both phytoplankton species was inhibited with increasing crude oil concentrations. Crude oil exposure did not affect Chl a content significantly in cells. SOD activities showed similar responses in both species, being enhanced at 4- and 8-mg/L crude oil exposure. Only H. triquetra demonstrated enhanced activity in GSSG pool and lipid peroxidation at 8-mg/L crude oil exposure, suggesting that phytoplankton species have distinct physiological responses and tolerance levels to crude oil exposure. This study indicated the activation of reactive oxygen species (ROS) in phytoplankton under crude oil exposure; however, the progressive damage in cells is still unknown. Thus, ROS-related damage in nucleic acid, lipids, proteins, and DNA, due to crude oil exposure could be a worthwhile subject of study to better understand crude oil toxicity at the base of the food web.

The effect of sublethal concentrations of the water-soluble fraction of crude oil on the chemosensory function of Caspian roach, Rutilus caspicus (YAKOVLEV, 1870).

The water-soluble fraction of crude oil is a complex and toxic mixture of hydrocarbons. Because aquatic organisms directly encounter it, the water-soluble fraction plays an important role in the toxicity of crude oil in aquatic environments. To determine whether fish are attracted to or avoid the water-soluble fraction, Caspian roaches (Rutilus caspicus) were exposed to different concentrations of the water-soluble fraction in a choice maze apparatus. The results showed that Caspian roaches can detect and avoid 2 mg/L of the water-soluble fraction. To study the effect of the water-soluble fraction on the olfactory function of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction for 96 h; afterward, exposed fish encountered food extract in a choice maze apparatus. The present study showed that the water-soluble fraction significantly impairs the olfactory function of roaches. To investigate the effect of olfactory system dysfunction on the feeding behavior of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction. After 4 d, 8 d, and 12 d of exposure, the feeding behavior toward the food extract was tested. The results showed that both 3.2 mg/L and 16 mg/L of the water-soluble fraction suppress the feeding behavior of Caspian roaches. The present study demonstrates that sublethal concentrations of crude oil's water-soluble fraction impair the olfactory function of fish and consequently suppress the feeding behavior.

Evaluation of Trace Metals and Physical Properties of Nigerian Crude Oil Saturate Fraction

Analyses of trace elements and physical properties of the saturate fraction of Nigerian crude oil were done in order to establish the characteristics that may aid the developmental processes of the natural resources. Crude oil samples were collected from three different oil fields in Niger-Delta area of Nigeria. The saturate fractions were eluted by column chromatography using n-hexane. The saturate fractions were investigated for functional groups using Fourier transform infrared spectrometry (FT–IR); the elemental concentrations were determined using Atomic absorption spectrometry, while the physical properties (flash point, ash content, refractive index, and color) were determined using standard analytical methods. The results revealed that the infrared spectra of the saturate fraction of the Nigerian crude oil showed mainly the presence of C-H(CH3) and C-H(CH2) functional groups, indicating high purity of the samples. The concentrations of the analyzed elements (Mn, Cu, Co, Zn, Fe, V, Cr, and Ni) in the saturate fraction were generally low compared to other fractions of Nigerian crude oil. This study revealed that Co has the highest mean concentration of 1.81 ± 0.36 mg/L, while Mn has the lowest mean concentration of 0.04 ± 0.02 mg/L. The t test values for the comparison of the elemental concentrations of Nigerian crude oil /saturate fraction and crude oil asphaltene/saturate fraction showed significant difference (except Mn) with respect to Nigerian crude oil /saturate fraction. The cluster analysis for the elements showed two groups, which are fairly well correlated indicating similar source and similar chemical affinity. The cross-plot analysis of the Nigerian crude oil and its saturate using elemental concentrations as the variables showed a strong positive inter element correlation since (R2 = 0.71), establishing a relationship between the Nigerian crude oil and the saturate fraction. The color of the saturate fraction ranged from off-white to colorless. The results of analysis provide useful information on its conversion mechanism and environmental implications of the development of the fossil fuel deposit.

Modeling Study of Crude Oil Enhanced Removal in a Two-Liquid Phase Partitioning Bioreactor

AbstractA combined process of solvent extraction and two-phase biodegradation was carried out to remove crude oil from water by mixed cultures, where silicone oil was selected as the organic solvent due to its biocompatibility and non-biodegradability. The crude oil removal and cell growth was experimentally studied. A simple model that combined steady mass transfer equations and dynamic growth kinetics of suspended cells was suggested to follow the entire process. Under the conditions studied, complete removal of crude oil from water was achieved at initial crude oil concentration of 5,000 mg/L. Results revealed that the proposed model satisfactorily described the process as long as crude oil level in the cell medium did not exceed the toxicity limit of suspended cells.

Accumulation of Hydrocarbons by Maize (Zea mays L.) in Remediation of Soils Contaminated with Crude Oil

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg−1) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg−1) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21–72.84%, while that of the corresponding controls was only 25.85–34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.

Unexpected interaction with dispersed crude oil droplets drives severe toxicity in Atlantic haddock embryos.

The toxicity resulting from exposure to oil droplets in marine fish embryos and larvae is still subject for debate. The most detailed studies have investigated the effects of water-dissolved components of crude oil in water accommodated fractions (WAFs) that lack bulk oil droplets. Although exposure to dissolved petroleum compounds alone is sufficient to cause the characteristic developmental toxicity of crude oil, few studies have addressed whether physical interaction with oil micro-droplets are a relevant exposure pathway for open water marine speices. Here we used controlled delivery of mechanically dispersed crude oil to expose pelagic embryos and larvae of a marine teleost, the Atlantic haddock (Melanogrammus aeglefinus). Haddock embryos were exposed continuously to two different concentrations of dispersed crude oil, high and low, or in pulses. By 24 hours of exposure, micro-droplets of oil were observed adhering and accumulating on the chorion, accompanied by highly elevated levels of cyp1a, a biomarker for exposure to aromatic hydrocarbons. Embryos from all treatment groups showed abnormalities representative of crude oil cardiotoxicity at hatch (5 days of exposure), such as pericardial and yolk sac edema. Compared to other species, the frequency and severity of toxic effects was higher than expected for the waterborne PAH concentrations (e.g., 100% of larvae had edema at the low treatment). These findings suggest an enhanced tissue uptake of PAHs and/or other petroleum compounds from attached oil droplets. These studies highlight a novel property of haddock embryos that leads to greater than expected impact from dispersed crude oil. Given the very limited number of marine species tested in similar exposures, the likelihood of other species with similar properties could be high. This unanticipated result therefore has implications for assessing the ecological impacts of oil spills and the use of methods for dispersing oil in the open sea.

Investigation of petroleum-contaminated groundwater remediation using multi-stage pilot system: physical and biological approach

In this paper, a pilot-scale system including various process steps was investigated in order to treat contaminated groundwater supplies which have been exposed to oil pollutants for a long time as they are located near the Tehran oil refinery company (TORC). For achieving this goal, a combination of dissolved air flotation unit that is followed by activated sludge bioreactors (ASBRs) and an activated carbon filter was chosen. The crude oil combined with tap water was applied to synthesize contaminated groundwater. Activated sludge taken from wastewater treatment plant at TORC was used to supply oil-degrading bacteria. Besides, the solution of mineral salts was added to the bioreactor as nutrients amendment. The optimum design parameters such as hydraulic retention time, return activated sludge rate of the ASBRs, and total residence time for all steps were 14 h, 100%, and 21 h, respectively. The operation of the pilot system which was implemented in different initial crude oil concentrations (206 ± 1,412 ± 3,1590 ± 10 mg l−1) finally led to total petroleum hydrocarbons removal of 97, 97.25, and 98.57%, respectively. The reduction efficiency of chemical oxygen demand during the experiment was more than 97%. Furthermore, the quality of the treated groundwater was clearly improved, as the turbidity reduction through the experiment exceeded 90%. According to the results of the study, this treatment system can be considered as a reliable and efficient approach that is recommended to be used in case of extremely contaminated groundwater.

Assessment of the toxicity of crude oil inSinonovacula constrictaclams

This study is aimed at investigating the toxic effects on clams (Sinonovacula constricta ) exposed to selected concentrations of individual crude oil: water accommodated fraction (WAF) and chemically enhanced (or dispersed) WAF (CEWAF). For this purpose, a study was performed on clams exposed to 0.04 mg L-1 and 0.01 mg L-1 WAF and CEWAF for 15 days, using parameters of antioxidant defense and oxidative damage. The accumulation of total petroleum hydrocarbon (TPH) in the gills of clams was dependent on time and dose, and CEWAF accumulation was higher than WAF accumulation. Exposure of clams to CEWAF oil resulted in significantly (p < 0.05) elevated ethoxyresorufin-O-deethylase (EROD) activity compared with exposure to controls. The level of EROD induction was concentration-related, as indicated by the induction observed in clams exposed to higher concentrations of CEWAF. Oxidative damage indicators (DNA strand breaks) were also measured in gills to assess the effects of the selected crude oil by alkaline unwinding assay. Results showed that DNA damage was significantly induced, except in the low-level groups of WAF, and different trends were detected with time of exposure. Significant correlations between TPH uptake and both EROD activity and DNA damage can be used as suitable tools for integrated levels of study on the biomarkers of crude oil exposure.

Seahorse (Hippocampus reidi) as a bioindicator of crude oil exposure

This study explored the suitability of the seahorse Hippocampus reidi (Ginsburg, 1933) for assessing biomarkers of genotoxic effects and its use as a sentinel organism to detect the effects of acute exposure to petroleum hydrocarbons. Fish were exposed to three concentrations of crude oil (10, 20 and 30g/kg) for 96h, and the activity of phase II biotransformation enzyme glutathione S-transferase (GST) was measured. In addition, we performed genotoxicity assays, such as comet assay, micronucleus (MN) test and nuclear abnormalities (NA) induction, on the erythrocytes of the fish species. Our results revealed that the inhibition of hepatic GST activity in H. reidi was dependent on increasing crude oil concentrations. In contrast, an increase in the damage index (DI) and MN frequency were observed with increased crude oil concentrations. These results indicate that the alkaline comet assay and micronucleus test were suitable and useful in the evaluation of the genotoxicity of crude oil, which could improve determinations of the impact of oil spills on fish populations. In addition, H. reidi is a promising “sentinel organism” to detect the genotoxic impact of petroleum hydrocarbons.

English

A study was carried out in a screen house to determine the bacterial population dynamics in a crude oil soil undergoing bioremediation. The agricultural soil samples were polluted with different concentrations (5, 8 and 11%) of crude oil. Physiochemical and microbiological analyses were carried out on the polluted and unpolluted soil samples at various intervals beginning from two weeks after the pollution of the soil samples to the fourteenth week. The soil samples were found to be acidic (5.40) and rich in phosphorous (26.52 mg/kg). There were no significant differences in the pH, organic matter, sodium, potassium and magnesium of the unpolluted and the polluted soil samples. The microbial loads of the polluted soil samples were lower than the unpolluted soil samples throughout the study. The highest bacterial loads (27.00d&plusmn;2.20, 19.40c&plusmn;1.80, 8.70b&plusmn;0.50 for 5, 8 and 11% crude oil concentration respectively) were observed, when Ewingella americana (bacterium with known crude oil degrading ability) was inoculated into the polluted soil samples. The bacterial species responsible for the bioremediation from the polluted soil samples were identified using conventional techniques. The bacterial species isolated and identified were Pseudomonas aeruginosa, Bacillus subtilis, Bacillus cereus, Proteus vulgaris and Staphylococcus aureus. Bacillus spp has the highest percentage frequency (Bacillus subtilis = 30.95% and Bacillus cereus = 21.43%). The consistent isolation of these bacteria shows that they could survive the crude oil pollution and possibly utilize the crude oil, thereby making the crude oil less harmful to the environment. Key words: Bacteria, bioremediation, bacterial species, crude oil.