Hydrocarbon Degradation Ability Research Articles

Mitigation of hydrocarbon toxicity using bacterial consortium in microcosm environment for agrarian fecundity

Petroleum contamination in the soil has been well emphasized as a toxic and hazardous soil pollution contributing to a significant portion of soil infertility worldwide. In the present study, bacterial consortium CHM1 composed of 5 strains belonging to genera Klebsiella, Pantoea, and Enterobacter was evaluated for hydrocarbon degradation ability in the soil environment, as well as their performance in remediating ecotoxicity and phytotoxicity. Initially, the degradation efficiency (1.98%/day) in the soil environment was evaluated. Scanning Electron Microscopy combined with Energy Dispersive X-ray spectroscopy revealed an increase in nitrogen content by 24.98% and a decrease in carbon content by 22.76% implying an improvement in soil fertility. The Fourier Transform InfraRed spectroscopy and Gas Chromatographic analysis revealed significant depletion of aromatic, cyclic, long aliphatic, and complex acid and ester content of the test soil. Moreover, the quantitative PCR analysis exhibited the non-competitive coexistence of each component of the CHM1 consortium. Different enzymatic assays revealed elevated dehydrogenase and superoxide dismutase activity in the degradation system due to the introduction of CHM1 in the soil microcosm. Vibrio fischeri-assisted ecotoxicity analysis had established the potential of CHM1 to efficiently minimize the ecotoxicity of hydrocarbon contamination. The phytotoxicity analysis was performed using four different plant models viz. Chickpeas (Cicer arientinum), Coriander (Coriandrum sativum), Fenugreek (Trigonella foenum-graecum), and Spinach (Spinacia oleracea) exhibiting CHM1 amendment helped to restore plant germination and growth in hydrocarbon-contaminated soil system efficiently. The promising results from this study indicated the possible application of the bacterial consortium in hydrocarbon-contaminated land management and soil restoration for cultivation or other plantation purposes.

Genome analysis of a coral-associated bacterial consortium highlights complementary hydrocarbon degradation ability and other beneficial mechanisms for the host

Here we report the oil degradation genetic potential of six oil-degrading bacteria (ODB), previously used as a bioremediation consortium, isolated from the hydrocoral Millepora alcicornis and seawater. The strains were identified as Halomonas sp. (LC_1), Cobetia sp. (LC_6), Pseudoalteromonas shioyasakiensis (LC_2), Halopseudomonas aestusnigri (LC_3), Shewanella algae (LC_4), and Brucella intermedia (LC_5). The taxonomic identification differed from that of the original paper when we used whole genome gene markers instead of just 16S rRNA gene. Genes responsible for the degradation of aromatic hydrocarbons and n-alkanes were found in all genomes, although different (and complementary) steps of the metabolic pathways were unique to each strain. Genes for naphthalene and toluene degradation were found in various strains. We annotated quinate degradation genes in LC_6, while LC_3 and LC_5 presented genes for biosurfactant and rhamnolipid biosynthesis. We also annotated genes related to beneficial mechanisms for corals, such as genes involved in nitrogen and DMSP metabolism, cobalamin biosynthesis and antimicrobial compounds production. Our findings reinforce the importance of using bacterial consortia for bioremediation approaches instead of single strains, due to their complementary genomic arsenals. We also propose a genome-based framework to select complementary ODB that can provide additional benefits to coral health.

Combined Omics Approach Reveals Key Differences between Aerobic and Microaerobic Xylene-Degrading Enrichment Bacterial Communities: Rhodoferax─A Hitherto Unknown Player Emerges from the Microbial Dark Matter.

Among monoaromatic hydrocarbons, xylenes, especially the ortho and para isomers, are the least biodegradable compounds in oxygen-limited subsurface environments. Although much knowledge has been gained regarding the anaerobic degradation of xylene isomers in the past 2 decades, the diversity of those bacteria which are able to degrade them under microaerobic conditions is still unknown. To overcome this limitation, aerobic and microaerobic xylene-degrading enrichment cultures were established using groundwater taken from a xylene-contaminated site, and the associated bacterial communities were investigated using a polyphasic approach. Our results show that the xylene-degrading bacterial communities were distinctly different between aerobic and microaerobic enrichment conditions. Although members of the genus Pseudomonas were the most dominant in both types of enrichments, the Rhodoferax and Azovibrio lineages were only abundant under microaerobic conditions, while Sphingobium entirely replaced them under aerobic conditions. Analysis of a metagenome-assembled genome of a Rhodoferax-related bacterium revealed aromatic hydrocarbon-degrading ability by identifying two catechol 2,3-dioxygenases in the genome. Moreover, phylogenetic analysis indicated that both enzymes belonged to a newly defined subfamily of type I.2 extradiol dioxygenases (EDOs). Aerobic and microaerobic xylene-degradation experiments were conducted on strains Sphingobium sp. AS12 and Pseudomonas sp. MAP12, isolated from the aerobic and microaerobic enrichments, respectively. The obtained results, together with the whole-genome sequence data of the strains, confirmed the observation that members of the genus Sphingobium are excellent aromatic hydrocarbon degraders but effective only under clear aerobic conditions. Overall, it was concluded that the observed differences between the bacterial communities of aerobic and microaerobic xylene-degrading enrichments were driven primarily by (i) the method of aromatic ring activation (monooxygenation vs dioxygenation), (ii) the type of EDO enzymes, and (iii) the ability of degraders to respire utilizing nitrate.

Mechanism of visible light enhances microbial degradation of Bisphenol A.

Bisphenol A (BPA) is a toxic endocrine disruptor detected in various environments. Microbial metabolic/enzymatic degradation has been thought to be the main pathway for BPA attenuation in natural environments. In this study, we found that under visible light conditions, superoxide produced by bacteria was the main reason for the rapid removal of BPA, accounting for 57% of the total removal rate. With visible light, the bacteria degraded BPA at a rate of 0.22mg/L/d, and the total removal within 8 days reached 85%, which is 4.7 times compared with that of dark culture. The intermediate product 4-iso-propenylphenol, which was considered as an end-product of microbial degradation of BPA in previous reports, was detected in large quantities at 24h in culture but gradually decreased in our experiment. Community analysis suggested bacteria with aromatic hydrocarbon degradation ability were more enriched under light incubation. Moreover, the bacteria showed well degradation ability to various pharmaceutically active but nonbiodegradable compounds including diclofenac and fluoxetine, with a removal rate of 88 % and 20%, respectively. Our study revealed the organic pollutant transformation pathway under the combined action of light and microorganisms, providing new insights into the microbial treatment of aromatic hydrocarbon pollutants.

A deeper insight into the phytoremediation of soil polluted with petroleum hydrocarbons supported by the Enterobacter ludwigii ZCR5 strain

The Enterobacter ludwigii ZCR5 strain, isolated from the leaves of Zea mays growing in soil cocontaminated with hydrocarbons and heavy metals, was investigated under laboratory conditions for its plant growth-promoting traits, petroleum hydrocarbon (PH) degradation and biosurfactant production abilities and then used in bacterial-assisted phytoremediation. The whole genome of the ZCR5 was sequenced, and the presence of several genes encoding enzymes important for the enhancement of phytoremediation of soil polluted with PHs was detected. Next, the ZCR5 strain was introduced into polluted soil planted with Lolium perenne cv. Pinia. After inoculation, the ZCR5 strain was able to survive in polluted soil and colonized plant tissues. The highest efficacy of PHs removal (30.6 %) was observed for soil bioaugmented with living cells of the ZCR5, whereas in soil treated with bacterial necromass, it reached a value of 17.6 %. During the experimental period, the mechanisms enhancing the phytoremediation of PH-polluted soils were also tested in situ through the quantification of the expression of selected genes. The expression of genes encoding proteins involved in the biosurfactant production and promotion of plant growth by the ZCR5 strain was not detected either in the rhizosphere or in the endosphere of ryegrass. Among the genes involved in the degradation of PH, only CYP153 (in the rhizo- and endo-spheres) and nahAC (in the rhizosphere) were expressed. Despite the fact that we observed a higher efficiency of phytoremediation in the ZCR5-bioaugmented soil than in the controls, we were not able to indicate the bacterial mechanisms responsible for the observed effect of phytoremediation enhancement by the ZCR5 strain. The results obtained in our experiments indicate the necessity to study bacterial-plant interactions during assisted phytoremediation at the more detailed level. Thus the metatranscriptomic analysis of bacterial activity will be performed in the next step.

Differences in geological conditions have reshaped the structure and diversity of microbial communities in oily soils

High-throughput sequencing was used to study the microbial community structure diversity changes in oil-contaminated soils under different spatial distances and environmental conditions. 239 Phyla, 508 Classes, 810 Orders, 1417 Families, 2048 Genera, 511 Species of microbial communities were obtained from 16 samples in three regions. The physicochemical properties of the soil, microorganisms' community structure has been changed by Petroleum hydrocarbon (PHA). Alpha diversity results showed that the soil contained high bacterial diversity, especially in Qingyang's loess soil. The bacterial abundance was in the order of loess soil > black soil > sandy soil. Beta diversity revealed that spatial distance limitation and random variation of repeated samples may be the main factors leading to soil heterogeneity and microbial community structure differences. The dominant bacteria phyla with broad petroleum hydrocarbon degradation ability such as Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were identified. Pseudomonas, Bacillus, Nocardioides, Oceanobacillus, Sphingomonas, Alkanindiges and Streptomyces were identified as functional microbial for the PHA degradation. The microbial communities manifested the co-exclusion under different geological conditions, and played the key role in the soil PHA degradation through amino acid metabolism, energy metabolism and carbohydrate metabolism. The correlation results of amos structural equation showed that the diversity and abundance of soil microorganisms in different regions were controlled by soil PHA content and environmental factors. Altitude, annual average temperature and annual rainfall were positively correlated with microbial diversity. Annual rainfall and soil physical and chemical factors exhibited the most significant influence on it. Microbial diversity indirectly affected the PHA content in different type soil. We believe that reshape the structure and diversity of microbial communities in soil could be changed and reshaped by different geological conditions, pollutants and soil type. This study can provide helps for understanding the ecological effect of geomicrobiology formation under the driving force of geographic environment and other factors.

Trifluralin Impacts Soil Microbial Community and Functions

A 3-month experiment was designed to research the impact of trifluralin (TFL) on soil microbial communities and functions under the condition of greenhouse. In this work, silty loam from Langfang was treated with three doses of TFL (1,260, 12,600, and 126,000 g ha−1) and incubated for 90 days. The half-lives of TFL were 15–23 days in all cases. The bacterial and fungal diversities and community structures were impacted by TFL. The bacterial functions of chemoheterotrophy and sulfur oxidation were decreased shortly, but the hydrocarbon degradation ability was significantly increased in the results of functional annotation of prokaryotic taxa (FAPROTAX). For the predicted results of Tax4Fun, amino acid (arginine and proline) metabolism and ABC transporter were decreased significantly, while nitrogen metabolism and ribosome translation were significantly increased. In conclusion, this work aids us to understand the risk of TFL in soil more comprehensively.

Remediation of petroleum hydrocarbon contaminated soil using hydrocarbonoclastic rhizobacteria, applied through Azadirachta indica rhizosphere

Crude oil/petroleum hydrocarbons (PHs) are major pollutants worldwide. In the present study, three bacterial isolates -Pseudomonas aeruginosa BB-BE3, P. aeruginosa BBBJ, and Gordonia amicalis BB-DAC were selected for their efficient hydrocarbon degradation and plant growth promotion (PGP) abilities. All three isolates were positive for siderophore production, phosphate solubilization, and IAA production, even in the presence of crude oil. The rhizoremediation ability was validated through pot trials where all three isolates promoted the growth of the Azadirachta indica plant in crude oil-contaminated soils. Treatment with the combination of the plant (A. indica) and bacteria, i.e., Pseudomonas aeruginosa BB-BE3; P. aeruginosa BBBJ; Gordonia amicalis BB-DAC showed 95.71, 93.28, and 89.88% removal of TPHs respectively, while the treatment with the plant (only) resulted in 13.44% removal of TPHs whereas, in the control (Sterile bulk soil + Crude oil), the hydrocarbon removal percentage was only 5.87%. The plant tissues were analyzed for catalase (CAT) and peroxidase (POX) activities, and the plants augmented with bacterial strains had significantly low CAT and POX activities as compared to uninoculated control. Therefore, the results suggest that the A. indica plant, in symbiotic association with these hydrocarbonoclastic rhizobacteria, could be used for bioremediation of crude oil-polluted soil.

Genetic and Comparative Genome Analysis of Exiguobacterium aurantiacum SW-20, a Petroleum-Degrading Bacteria with Salt Tolerance and Heavy Metal-Tolerance Isolated from Produced Water of Changqing Oilfield, China.

The genome of Exiguobacterium aurantiacum SW-20 (E. aurantiacum SW-20), a salt-tolerant microorganism with petroleum hydrocarbon-degrading ability isolated from the Changqing Oilfield, was sequenced and analyzed. Genomic data mining even comparative transcriptomics revealed that some genes existed in SW-20 might be related to the salt tolerance. Besides, genes related to petroleum hydrocarbon degradation discovered in genomic clusters were also found in the genome, indicating that these genes have a certain potential in the bioremediation of petroleum pollutants. Multiple natural product biosynthesis gene clusters were detected, which was critical for survival in the extreme conditions. Transcriptomic studies revealed that some genes were significantly up-regulated as salinity increased, implying that these genes might be related to the salt tolerance of SW-20 when living in a high salt environment. In our study, gene clusters including salt tolerance, heavy metal tolerance and alkane degradation were all compared. When the same functional gene clusters from different strains, it was discovered that the gene composition differed. Comparative genomics and in-depth analysis provided insights into the physiological features and adaptation strategies of E. aurantiacum SW-20 in the oilfield environment. Our research increased the understanding of niches adaption of SW-20 at genomic level.

Response of the bacterial metagenome in port environments to changing environmental conditions

Port environments are highly dynamic and hotspots for marine bioinvasion. This study investigated the bacterial diversity at two geographically distant ports (Mangalore-marine port; and Haldia-riverine port) using next-generation sequencing during southwest monsoon and non-monsoon (Pre-monsoon) seasons. During southwest monsoon, at both marine and riverine ports, operational taxonomic units (OTUs) affiliated to bacteria reported to have hydrocarbon degrading ability were observed. Whereas during pre-monsoon, a significant increase in benthic bacterial OTUs was evident at the marine port, and the riverine port was characterized by oceanic species OTUs. Results suggest that the dynamics of prevalent environmental conditions, driven by seasons, led to emergence of ecologically relevant bacteria, many of which have been observed for the first time in Indian coastal waters. Their presence could be used as indicators of prevailing environmental conditions and nature of anthropogenic influence in port ecosystems. Unravelling functional roles of such ecologically relevant species is a way forward.

Statistical Optimisation of Diesel Biodegradation at Low Temperatures by an Antarctic Marine Bacterial Consortium Isolated from Non-Contaminated Seawater.

Hydrocarbon pollution is widespread around the globe and, even in the remoteness of Antarctica, the impacts of hydrocarbons from anthropogenic sources are still apparent. Antarctica’s chronically cold temperatures and other extreme environmental conditions reduce the rates of biological processes, including the biodegradation of pollutants. However, the native Antarctic microbial diversity provides a reservoir of cold-adapted microorganisms, some of which have the potential for biodegradation. This study evaluated the diesel hydrocarbon-degrading ability of a psychrotolerant marine bacterial consortium obtained from the coast of the north-west Antarctic Peninsula. The consortium’s growth conditions were optimised using one-factor-at-a-time (OFAT) and statistical response surface methodology (RSM), which identified optimal growth conditions of pH 8.0, 10 °C, 25 ppt NaCl and 1.5 g/L NH4NO3. The predicted model was highly significant and confirmed that the parameters’ salinity, temperature, nitrogen concentration and initial diesel concentration significantly influenced diesel biodegradation. Using the optimised values generated by RSM, a mass reduction of 12.23 mg/mL from the initial 30.518 mg/mL (4% (w/v)) concentration of diesel was achieved within a 6 d incubation period. This study provides further evidence for the presence of native hydrocarbon-degrading bacteria in non-contaminated Antarctic seawater.

Indigenous microbial strains as bioresource for remediation of chronically polluted Niger Delta soils

An increase in artisanal crude oil refining within the Niger Delta Creeks has led to colossal environmental problems occasioned by spillages and subsequent ecosystem damage. Bacteria have been shown to play key role in biogeochemical cycling and degradation of pollutants from petroleum sources. The present study investigated the degradation efficiency of a bacterial consortia recovered from heavily inundated site in Bie-Ama community, having total petroleum hydrocarbons (TPH) concentration of 22,000 mg/kg, a value higher than Department of Petroleum Resources (DPR)’s 1000 mg/kg intervention limit. Soil samples were collected at 15 cm depth with soil auger while microbial isolation was done using enrichment and vapor phase transfer methods in Bushnell Haas medium. Colorimetric method using 2, 6-dichlorophenol indophenol (DCPIP) redox indicator was employed to determine biodegradation potentials of isolates. Bacterial isolates identified using 16S rRNA gene by Sanger sequencing were further screened for biosurfactant production and aromatic hydrocarbon degradation abilities. A consortium for efficient biodegradation of crude oil was constituted from individual isolates that totally decolorized DCPIP. Total culturable heterotrophic and hydrocarbon utilizing bacterial counts were 2.07 × 106 and 1.71 × 106 CFU/g soil respectively. Bacterial strains from the genera Pseudomonas, Bacillus, Klebsiella, Enterobacter produced biosurfactants while all strains utilized aromatics (benzene and naphthalene). A combination of Pseudomonas, Bacillus, Lysinibacillus and Enterobacter was the most efficient crude oil degrading consortium with significant mean difference (p = 0.05) as evidenced by GC-analysis confirming a more than 25% reduction in total petroleum hydrocarbon (TPH) concentration of 1% crude oil within 48 h. Conclusively, the extant indigenous bacterial community in the impacted site has the natural capability to degrade hydrocarbons and could be further enhanced through biostimulation for in situ remediation.

Complete genome sequence and comparative genome analysis of Alcanivorax sp. IO_7, a marine alkane-degrading bacterium isolated from hydrothermally-influenced deep seawater of southwest Indian ridge

Genome of Alcanivorax sp. IO_7, an alkane degrading deep-sea bacteria isolated from hydrothermally-influenced Southwest Indian Ridge was sequenced and analysed. Genomic data mining revealed gene clusters for degrading n-alkane and cycloalkanes, including biosurfactant production. The strain was shown to grow on hexadecane as its sole carbon source, supporting the findings of genomic analysis. Presence of cyclohexanone monooxygenase among genomic islands suggest that this strain may have used gene transfer to enhance its hydrocarbon degradation ability. Genes encoding for heavy metal resistance, multidrug resistance and multiple natural product biosynthesis crucial for survival in the hydrothermally influenced deep sea environment were detected. In our comparative genome analysis, it was evident that marine Alcanivorax strains contain a suite of enzymes for n-alkane and haloalkanoate degradation. Comparative genome and genomic synteny analysis provided insights into the physiological features and adaptation strategies of Alcanivorax sp. IO_7 in the deep-sea hydrothermal environment.

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.

Isolation and characterization of hydrocarbon-degrading bacteria from gas station leaking-contaminated groundwater in the Southern Amazon, Brazil.

Twenty-three hydrocarbon-degrading bacteria strains were isolated from gas station leaking-contaminated groundwater located in the Southern Amazon, Brazil. Based on hydrocarbon (diesel, hexadecane, benzene, toluene and xylene) degradation ability, two strains were selected for further study. The amplification and sequencing of the 16S rRNA gene showed that these two strains belonged to the genus Bacillus (Bacillus sp. L26 and Bacillus sp. L30). GC-MS analysis showed that strain L30 was the most effective in degrading n-alkane (C10-C27) from diesel after 7 days of cultivation in mineral medium. Both strains produced biosurfactants and showed emulsification activity, specially the strain L30. Alkane hydroxylase gene (group III), which is important for alkane biodegradation, was present in strains. As a result, this study indicated that these bacteria could have promising applications in hydrocarbon bioremediation.

Exploring the genetic potential of a fosmid metagenomic library from an oil-impacted mangrove sediment for metabolism of aromatic compounds.

Aromatic hydrocarbons (AH) are widely distributed in nature, and many of them have been reported as relevant environmental pollutants and valuable carbon sources for different microorganisms. In this work, high-throughput sequencing of a metagenomic fosmid library was carried out to evaluate the functional and taxonomic diversity of genes involved in aromatic compounds degradation in oil-impacted mangrove sediments. In addition, activity-based approach and gas chromatography were used to assess the degradation potential of fosmid clones. Results indicated that AH degradation genes, such as monooxygenases and dioxygenases, were grouped into the following categories: anaerobic degradation of aromatic compounds (20.34%), metabolism of central aromatic intermediates (35.40%) and peripheral pathways for catabolism of aromatic compounds (22.56%). Taxonomic affiliation of genes related to aromatic compounds metabolism revealed the prevalence of the classes Alphaproteobacteria, Actinobacteria, Betaproteobacteria, Gammaproteobacteria and Deltaproteobacteria. Aromatic hydrocarbons (phenol, naphthalene, phenanthrene, pyrene and benzopyrene) were used as the only carbon source to screen clones with degradation potential. Of the 2500 clones tested, 48 showed some respiratory activity in at least one of the five carbon sources used. The hydrocarbon degradation ability of the top ten fosmid clones was confirmed by GC-MS. Further, annotation of assembled metagenomic fragments revealed ORFs corresponding to proteins and functional domains directly or indirectly involved in the aromatic compound metabolism, such as catechol 2,3-dioxygenase and ferredoxin oxidoreductase. Finally, these data suggest that the indigenous mangrove sediment microbiota developed essential mechanisms towards ecosystem remediation of petroleum hydrocarbon impact.

Biological Degradation of Polycyclic Aromatic Compounds (PAHs) in Soil: a Current Perspective

Here we examine recent research on the degradation of polyaromatic hydrocarbons (PAHs) by fungi and bacteria. In addition, we provide information regarding the role that omics tools (next-generation sequencing) can play in the future development of bioremediation of PAHs. The toxicity of petrogenic wastes containing PAHs to biotic communities, including humans, is well established. Bioremediation strategies based on the use of microorganisms represent an economic and environmentally friendly approach (compared with other remediation methods) which is increasingly being applied for the treatment of PAH-contaminated soils. Biological treatments or bioremediation exploits the hydrocarbon-degrading abilities of microorganisms, resulting in destruction of the contaminants and significant detoxification of the contaminated material. To further develop this approach as a consistent commercial technology, it is important to understand the microbial ecology of the remediation process, determining the key microorganisms which drive the underlying PAH degradation processes.

Characterisation of microbial communities of drill cuttings piles from offshore oil and gas installations

Drill cuttings (DC) are produced during hydrocarbon drilling operations and are composed of subsurface rock coated with hydrocarbons and drilling fluids. Historic disposal of DC at sea has resulted in the formation of large piles on the seabed that may be left in situ following infrastructure decommissioning. This study provides a first insight into the microbial abundance, diversity and community structure of two DC piles from North Sea oil and gas installations. The abundance of both bacteria and archaea was lower in DC than in surrounding natural sediments. Microbial diversity and richness within DC were low but increased with distance from the piles. Microbial community structure was significantly different in DC piles compared to nearby natural sediments. DC bacterial communities were dominated by Halomonas, Dietzia and Dethiobacter. The presence of such organisms suggests a potential function of hydrocarbon degradation ability and may play an active role in DC pile remediation.

Environmental Aspects of the Use of Hedera helix Extract in Bioremediation Process.

This paper analyzes the impact of saponins from English ivy leaves on the properties of environmental bacterial strains and hydrocarbon degradation ability. For this purpose, two bacterial strains, Raoultella ornitinolytica M03 and Acinetobacter calcoaceticus M1B, have been used in toluene, 4-chlorotoluene, and α,α,α-trifluorotoluene biodegradation supported by Hedera helix extract. Moreover, theeffects of ivy exposition on cell properties and extract toxicity were investigated. The extract was found to cause minor differences in cell surface hydrophobicity, membrane permeability, and Zeta potential, although it adhered to the cell surface. Acinetobacter calcoaceticus M1B was more affected by the ivy extract; thus, the cells were more metabolically active and degraded saponins at greater amounts. Although the extract influenced positively the cells’ viability in the presence of hydrocarbons, it could have been used by the bacteria as a carbon source, thus slowing down hydrocarbon degradation. These results show that the use of ivy saponins for hydrocarbon remediation is environmentally acceptable but should be carefully analyzed to assess the efficiency of the selected saponins-rich extract in combination with selected bacterial strains.

Degradation of poly aromatic fractions of crude oil and detection of catabolic genes in hydrocarbon-degrading bacteria isolated from Agbabu bitumen sediments in Ondo State.

Pollution due to release of Poly aromatic hydrocarbons (PAHs) are a major environmental issue especially in oil producing communities. This study investigates the polyaromatic hydrocarbon degradation potentials of some bacteria: Campylobacter hominis, Bacillus cereus, Dyadobacter koreensis, Pseudomonas aeruginosa and Micrococcus luteus isolated from Agbabu bitumen sediments in Ondo State. The isolates were used singly and in consortium for the degradation of Bonny light crude oil. Concentrations of residual aromatic hydrocarbons in crude oil degraded by these isolates were determined by Gas chromatography/Mass Spectroscopy with flame ionization detector (FID). Detection of catabolic genes (nahH, CatA and AlkB) in the isolates was determined by PCR amplification of their specific primers. The GC-MS analyses showed degradation of poly aromatic hydrocarbons (PAHs) by these isolates. The consortium exhibited the highest PAH reduction (73%) while C. hominis had the least PAH reduction (56%). Dyadobacter koreensis, P. aeruginosa, Micrococcus luteus and B. cereus, displayed 66%, 60%, 59% and 58% PAH reduction respectively. The catabolic gene nahH gene was present in B. cereus, D. koreensis, P. aeruginosa and M. luteus, alkB gene was present in B. cereus, C. hominis, and D. koreensis while CatA was not detected in any of the isolates. The findings of this study affirmed the hydrocarbon-degrading abilities and presence of catabolic genes in these bacteria, these make them potential tools in oil prospecting and cleaning up of hydrocarbon contaminated sites.