Bacterial crude oil and polyaromatic hydrocarbon degraders from Kazakh oil fields as barley growth support.

Bacterial strains of the genera Arthrobacter, Bacillus, Dietzia, Kocuria, and Micrococcus were isolated from oil-contaminated soils of the Balgimbaev, Dossor, and Zaburunye oil fields in Kazakhstan. They were selected from 1376 isolated strains based on their unique ability to use crude oil and polyaromatic hydrocarbons (PAHs) as sole source of carbon and energy in growth experiments. The isolated strains degraded a wide range of aliphatic and aromatic components from crude oil to generate a total of 170 acid metabolites. Eight metabolites were detected during the degradation of anthracene and of phenanthrene, two of which led to the description of a new degradation pathway. The selected bacterial strains Arthrobacter bussei/agilis SBUG 2290, Bacillus atrophaeus SBUG 2291, Bacillus subtilis SBUG 2285, Dietzia kunjamensis SBUG 2289, Kocuria rosea SBUG 2287, Kocuria polaris SBUG 2288, and Micrococcus luteus SBUG 2286 promoted the growth of barley shoots and roots in oil-contaminated soil, demonstrating the enormous potential of isolatable and cultivable soil bacteria in soil remediation. KEY POINTS: • Special powerful bacterial strains as potential crude oil and PAH degraders. • Growth on crude oil or PAHs as sole source of carbon and energy. • Bacterial support of barley growth as resource for soil remediation.

Current research on simultaneous oxidation of aliphatic and aromatic hydrocarbons by bacteria of genus Pseudomonas.

One of the most frequently used methods for elimination of oil pollution is the use of biological preparations based on oil-degrading microorganisms. Such microorganisms often relate to bacteria of the genus Pseudomonas. Pseudomonads are ubiquitous microorganisms that often have the ability to oxidize various pollutants, including oil hydrocarbons. To date, individual biochemical pathways of hydrocarbon degradation and the organization of the corresponding genes have been studied in detail. Almost all studies of this kind have been performed on degraders of individual hydrocarbons belonging to a single particular class. Microorganisms capable of simultaneous degradation of aliphatic and aromatic hydrocarbons are very poorly studied. Most of the works on such objects have been devoted only to phenotype characteristic and some to genetic studies. To identify the patterns of interaction of several metabolic systems depending on the growth conditions, the most promising are such approaches as transcriptomics and proteomics, which make it possible to obtain a comprehensive assessment of changes in the expression of hundreds of genes and proteins at the same time. This review summarizes the existing data on bacteria of the genus Pseudomonas capable of the simultaneous oxidation of hydrocarbons of different classes (alkanes, monoaromatics, and polyaromatics) and presents the most important results obtained in the studies on the biodegradation of hydrocarbons by representatives of this genus using methods of transcriptomic and proteomic analyses.

Biodegradation of binary mixtures of octane with benzene, toluene, ethylbenzene or xylene (BTEX): insights on the potential of Burkholderia, Pseudomonas and Cupriavidus isolates.

The contamination of the environment by crude oil and its by-products, mainly composed of aliphatic and aromatic hydrocarbons, is a widespread problem. Biodegradation by bacteria is one of the processes responsible for the removal of these pollutants. This study was conducted to determine the abilities of Burkholderia sp. B5, Cupriavidus sp. B1, Pseudomonas sp. T1, and another Cupriavidus sp. X5 to degrade binary mixtures of octane (representing aliphatic hydrocarbons) with benzene, toluene, ethylbenzene, or xylene (BTEX as aromatic hydrocarbons) at a final concentration of 100 ppm under aerobic conditions. These strains were isolated from an enriched bacterial consortium (Yabase or Y consortium) that prefer to degrade aromatic hydrocarbon over aliphatic hydrocarbons. We found that B5 degraded all BTEX compounds more rapidly than octane. In contrast, B1, T1 and X5 utilized more of octane over BTX compounds. B5 also preferred to use benzene over octane with varying concentrations of up to 200 mg/l. B5 possesses alkane hydroxylase (alkB) and catechol 2,3-dioxygenase (C23D) genes, which are responsible for the degradation of alkanes and aromatic hydrocarbons, respectively. This study strongly supports our notion that Burkholderia played a key role in the preferential degradation of aromatic hydrocarbons over aliphatic hydrocarbons in the previously characterized Y consortium. The preferential degradation of more toxic aromatic hydrocarbons over aliphatics is crucial in risk-based bioremediation.

Enzymatic C-H activation of aromatic compounds through CO2 fixation.

The direct C-H carboxylation of aromatic compounds is an attractive route to the corresponding carboxylic acids, but remains challenging under mild conditions. It has been proposed that the first step in anaerobic microbial degradation of recalcitrant aromatic compounds is a UbiD-mediated carboxylation. In this study, we use the UbiD enzyme ferulic acid decarboxylase (Fdc) in combination with a carboxylic acid reductase to create aromatic degradation-inspired cascade reactions, leading to efficient functionalization of styrene through CO2 fixation. We reveal that rational structure-guided laboratory evolution can expand the substrate scope of Fdc, resulting in activity on a range of mono- and bicyclic aromatic compounds through a single mutation. Selected variants demonstrated 150-fold improvement in the conversion of coumarillic acid to benzofuran + CO2 and unlocked reactivity towards naphthoic acid. Our data demonstrate that UbiD-mediated C-H activation is a versatile tool for the transformation of aryl/alkene compounds and CO2 into commodity chemicals.

Evaluation of Lignin-Modifying Enzyme Activity of Trametes spp. (Agaricomycetes) Isolated from Georgian Forests with an Emphasis on T. multicolor Biosynthetic Potential.

In this study, a wide diversity in lignin-modifying enzyme (LME) secretion by 11 Trametes spp. strains isolated from the forests of Georgia was revealed in their submerged cultivation in both synthetic and lignocellulose-based media. Among them, T. multicolor BCC 511 was distinguished by simultaneous production of laccase, manganese peroxidase (MnP), and lignin peroxidase (LiP) in the presence of high carbon and nitrogen concentrations. Mannitol at the concentration of 15 g/L provided an accumulation of 23.7 U/mL laccase and 0.56 U/mL MnP. Significant modulation of LME activity by lignocellulosic substrates, metals, aromatic compounds, and their concentrations was established. Mandarin peels manifold increased the fungus laccase and LiP activities, while the ethanol production residue and banana peels activated manganese-oxidizing and Phenol Red-oxidizing manganese peroxidases, respectively. The addition of 2 mM of copper sulfate to the control medium induced the laccase production 28-fold and did not significantly affect the MnP and LiP activities. Fe2+ at a concentration of 0.1 mM enhanced the fungus volumetric and specific laccase activities almost 8-fold; at a concentration of 0.25-0.5 mM, there was a 2-fold increase in the MnP activity. Mn2+ appeared to be an effective inducer of the Mn-oxidizing MnP, increasing specific activity of the enzyme 14-fold. Supplementation of the copper-containing medium with 1 mM veratryl alcohol or guaiacol favored laccase and MnP production. The high yields of laccase (110 U/mL), MnP (0.62 U/mL), and LiP (0.71 U/mL) obtained in a laboratory fermenter make T. multicolor 511 useful for industrial and environmental applications.

Periodically spilled-oil input as a trigger to stimulate the development of hydrocarbon-degrading consortia in a beach ecosystem.

In this study, time-series samples were taken from a gravel beach to ascertain whether a periodic oil input induced by tidal action at the early stage of an oil spill can be a trigger to stimulate the development of hydrocarbon-degrading bacteria under natural in situ attenuation. High-throughput sequencing shows that the microbial community in beach sediments is characterized by the enrichment of hydrocarbon-degrading bacteria, including Alcanivorax, Dietzia, and Marinobacter. Accompanying the periodic floating-oil input, dynamic successions of microbial communities and corresponding fluctuations in functional genes (alkB and RDH) are clearly indicated in a time sequence, which keeps pace with the ongoing biodegradation of the spilled oil. The microbial succession that accompanies tidal action could benefit from the enhanced exchange of oxygen and nutrients; however, regular inputs of floating oil can be a trigger to stimulate an in situ "seed bank" of hydrocarbon-degrading bacteria. This leads to the continued blooming of hydrocarbon-degrading consortia in beach ecosystems. The results provide new insights into the beach microbial community structure and function in response to oil spills.

Bioremediation of petroleum wastewater by hyper-phenol tolerant Bacillus cereus: Preliminary studies with laboratory-scale batch process.

Petroleum wastewater samples from oil refinery and oil exploration site were treated by hyper phenol-tolerant Bacillus cereus (AKG1 and AKG2) in laboratory-scale batch process to assess their bioremediation efficacy. Quality of the treated wastewater samples were analyzed in terms of removal of chemical oxygen demand (COD), total organic carbon (TOC) and ammonium nitrogen content, and improvement of biological oxygen demand (BOD). Adaptation of these bacteria to the toxic environment through structural changes in their cell membranes was also highlighted. Among different combinations, the co-culture of AKG1 and AKG2 showed the best performance in degrading the wastewater samples.

An experimental study on the formation of methoxyaromatics during pyrolysis of Eucalyptus pulverulenta: Yields and mechanisms.

The production of bio-oil rich in methoxyaromatics during catalytic pyrolysis of Eucalyptus pulverulenta (EP) was studied using a fixed-bed reactor in the temperature range of 300-500°C and the bio-oil composition was analyzed by using a GC-MS. The results showed that the highest bio-oil yield of 38.45wt% was obtained at 400°C in the presence of Na2CO3, and the concentration of methoxyaromatics reached the maximum value of 63.4%(area) in the bio-oil. The major methoxyaromatics identified in bio-oil were guaiacol, syringol, 4-ethyl-2-methoxy phenol, and 1,2,4-trimethoxybenzene. The analysis of gaseous products indicated that CO2 was the major gas at low-temperatures and concentrations of H2 and CH4 increased with increasing pyrolysis temperature. Na2CO3 promoted the formation of methoxyaromatics, while NaOH seems to have enhanced the formation of phenolics. The mechanism of the formation of methoxyaromatics during pyrolysis of EP was proposed.

Response of the bacterial community associated with a cosmopolitan marine diatom to crude oil shows a preference for the biodegradation of aromatic hydrocarbons.

Emerging evidence shows that hydrocarbonoclastic bacteria (HCB) may be commonly found associated with phytoplankton in the ocean, but the ecology of these bacteria and how they respond to crude oil remains poorly understood. Here, we used a natural diatom-bacterial assemblage to investigate the diversity and response of HCB associated with a cosmopolitan marine diatom, Skeletonema costatum, to crude oil. Pyrosequencing analysis and qPCR revealed a dramatic transition in the diatom-associated bacterial community, defined initially by a short-lived bloom of Methylophaga (putative oil degraders) that was subsequently succeeded by distinct groups of HCB (Marinobacter, Polycyclovorans, Arenibacter, Parvibaculum, Roseobacter clade), including putative novel phyla, as well as other groups with previously unqualified oil-degrading potential. Interestingly, these oil-enriched organisms contributed to the apparent and exclusive biodegradation of substituted and non-substituted polycyclic aromatic hydrocarbons (PAHs), thereby suggesting that the HCB community associated with the diatom is tuned to specializing in the degradation of PAHs. Furthermore, the formation of marine oil snow (MOS) in oil-amended incubations was consistent with its formation during the Deepwater Horizon oil spill. This work highlights the phycosphere of phytoplankton as an underexplored biotope in the ocean where HCB may contribute importantly to the biodegradation of hydrocarbon contaminants in marine surface waters.

Application of nitrate to enhance biodegradation of gasoline components in soil by indigenous microorganisms under anoxic condition.

Anaerobic/anoxic biodegradation of hydrocarbons offers an attractive approach to the removal of these compounds from polluted environments such as aquifers, aquatic sediments, submerged soils and subsurface soils. The application of nitrate was investigated to accelerate the degradation of gasoline components such as mono-aromatic hydrocarbons and total petroleum hydrocarbons (TPH) in soil by indigenous microorganisms under anoxic condition. The addition of nitrate had little effect on the degradation of mono-aromatic hydrocarbons m- & p-xylene, o-xylene, sec-butylbenzene and 1,2,4-trimethylbenzene, but facilitated the degradation of TPH (C6-C12) and mono-aromatic hydrocarbons toluene and ethylbenzene markedly. Furthermore, the more nitrate added, the higher the percentage of toluene, ethylbenzene and TPH (C6-C12) degraded after 180 days of anoxic incubation. Microorganisms capable of degrading toluene, ethylbenzene and TPH (C6-C12) with nitrate as the electron acceptor under anaerobic/anoxic condition are composed predominantly of Alpha-, Beta-, Gamma- or Delta-proteobacteria. Beta- and Gamma-proteobacteria were the main components of indigenous microorganisms, and accounted for 83-100% of the total amount of indigenous microorganisms in soil used in this study. Furthermore, the total amount of indigenous microorganisms increased with nitrate added. The addition of nitrate stimulated the growth of indigenous microorganisms, and therefore facilitated the degradation of toluene, ethylbenzene and TPH (C6-C12).

[Isolation and Identification of Petroleum Degradation Bacteria and Interspecific Interactions Among Four Bacillus Strains].

Six petroleum-degrading strains were isolated from oil-contaminated soil at Dagang oil field and oil sewage on Bohai offshore drilling platform in Tianjin using enrichment culture and isolation method. The physiological biochemical test together with 16S rDNA sequencing analysis indicated that they belonged to Bacillus (S1, S2, S3, S4), Pseudomonas (W1) and Ochrobactrum (W2), respectively. The strain S3 had the maximum degradation rate of alkane (41.3%) and aromatic hydrocarbon (30.9%) among all isolated strains showing the better degradation efficiency by endogenous bacteria when compared to that by the exogenous bacteria. The four Bacillus strains were used to construct microbiome, thereafter subjected to petroleum degradation efficiency test and analyzed. The results showed that microbiome F3 consisting of S1 and S4 had the maximum degradation rates of alkane (50.5%) and aromatic hydrocarbon (54.0%), which were 69.9% and 156.1% higher than those by single bacterium, respectively. Furthermore, they were 22.1% and 74.6% respectively higher than those by the most optimal degradation bacterium S3. Microbiome F4 consisting of S2 and S3 had the minimum degradation rates of alkane (18.5%) and aromatic hydrocarbon (18.9%) which were 55.3% and 39.0% lower than the degradation rates of single bacterium, respectively. The results also demonstrated that there were both microbial synergy promotion and antagonism inhibition among bacteria of the same genus in the petroleum degradation period. Bacteria with close affinity in Bacillus genus displayed mainly promoted petroleum degradation effect.

Bioremediation of Petrochemical Wastewater Containing BTEX Compounds by a New Immobilized Bacterium Comamonas sp. JB in Magnetic Gellan Gum.

In this study, we investigated the bioremediation of petrochemical wastewater containing BTEX compounds by immobilized Comamonas sp. JB cells. Three kinds of magnetic nanoparticles were evaluated as immobilization supports for strain JB. After comparison with Fe3O4 and a-Fe2O3 nanoparticles, r-Fe2O3 nanoparticle was selected as the optimal immobilization support. The highest biodegradation activity of r-Fe2O3-magnetically immobilized cells was obtained when the concentration of r-Fe2O3 nanoparticle was 120 mg L(-1). Additionally, the recycling experiments demonstrated that the degradation activity of r-Fe2O3-magnetically immobilized cells was still high and led to less toxicity than untreated wastewater during the eight recycles. qPCR suggested the concentration of strain JB in r-Fe2O3-magnetically immobilized cells was evidently increased after eight cycles of degradation experiments. These results supported developing efficient biocatalysts using r-Fe2O3-magnetically immobilized cells and provided a promising technique for improving biocatalysts used in the bioremediation of not only petrochemical wastewater but also other hazardous wastewater.

Bioremediation potential of microorganisms derived from petroleum reservoirs.

Bacterial strains and metagenomic clones, both obtained from petroleum reservoirs, were evaluated for petroleum degradation abilities either individually or in pools using seawater microcosms for 21 days. Gas Chromatography-Flame Ionization Detector (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS) analyses were carried out to evaluate crude oil degradation. The results showed that metagenomic clones 1A and 2B were able to biodegrade n-alkanes (C14 to C33) and isoprenoids (phytane and pristane), with rates ranging from 31% to 47%, respectively. The bacteria Dietzia maris CBMAI 705 and Micrococcus sp. CBMAI 636 showed higher rates reaching 99% after 21 days. The metagenomic clone pool biodegraded these compounds at rates ranging from 11% to 45%. Regarding aromatic compound biodegradation, metagenomic clones 2B and 10A were able to biodegrade up to 94% of phenanthrene and methylphenanthrenes (3-MP, 2-MP, 9-MP and 1-MP) with rates ranging from 55% to 70% after 21 days, while the bacteria Dietzia maris CBMAI 705 and Micrococcus sp. CBMAI 636 were able to biodegrade 63% and up to 99% of phenanthrene, respectively, and methylphenanthrenes (3-MP, 2-MP, 9-MP and 1-MP) with rates ranging from 23% to 99% after 21 days. In this work, isolated strains as well as metagenomic clones were capable of degrading several petroleum compounds, revealing an innovative strategy and a great potential for further biotechnological and bioremediation applications.

Application of a biofilm formed by a mixture of yeasts isolated in Vietnam to degrade aromatic hydrocarbon polluted wastewater collected from petroleum storage.

In this study, three good biofilm-forming yeast strains, including Candida viswanathii TH1, Candida tropicalis TH4 and Trichosporon asahii B1, were isolated from oil-contaminated water and sediment samples collected in coastal zones of Vietnam. These strains were registered in the GenBank database with the accession numbers JX129175, JX129176 and KC139404 for strain TH1, TH4 and B1, respectively. The biofilm formed by a mixture of these organisms degraded 90, 85, 82 and 67% of phenol, naphthalene, anthracene and pyrene, respectively, after a 7-day incubation period using an initial concentration of 600 ppm phenol and 200 ppm of each of the other compounds. In addition, this biofilm completely degraded these aromatic compounds, which were from wastewater collected from petroleum tanks in Do Xa, Hanoi after 14 days of incubation based on gas chromatography mass spectrometry analysis. To the best of our knowledge, reports on polycyclic aromatic hydrocarbon and phenol degradation by biofilm-forming yeasts are limited. The results obtained indicate that the biofilm formed by multiple yeast strains may considerably increase the degradation efficiency of aromatic hydrocarbon compounds, and may lead to a new approach for eliminating petroleum oil-contaminated water in Vietnam.

Intracellular hydrogen peroxide and superoxide poison 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase, the first committed enzyme in the aromatic biosynthetic pathway of Escherichia coli.

In Escherichia coli, aromatic compound biosynthesis is the process that has shown the greatest sensitivity to hydrogen peroxide stress. This pathway has long been recognized to be sensitive to superoxide as well, but the molecular target was unknown. Feeding experiments indicated that the bottleneck lies early in the pathway, and the suppressive effects of fur mutations and manganese supplementation suggested the involvement of a metalloprotein. The 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase (DAHP synthase) activity catalyzes the first step in the pathway, and it is provided by three isozymes known to rely upon a divalent metal. This activity progressively declined when cells were stressed with either oxidant. The purified enzyme was activated more strongly by ferrous iron than by other metals, and only this metalloform could be inactivated by hydrogen peroxide or superoxide. We infer that iron is the prosthetic metal in vivo. Both oxidants displace the iron atom from the enzyme. In peroxide-stressed cells, the enzyme accumulated as an apoprotein, potentially with an oxidized cysteine residue. In superoxide-stressed cells, the enzyme acquired a nonactivating zinc ion in its active site, an apparent consequence of the repeated ejection of iron. Manganese supplementation protected the activity in both cases, which matches the ability of manganese to metallate the enzyme and to provide substantial oxidant-resistant activity. DAHP synthase thus belongs to a family of mononuclear iron-containing enzymes that are disabled by oxidative stress. To date, all the intracellular injuries caused by physiological doses of these reactive oxygen species have arisen from the oxidation of reduced iron centers.

Phenol-oxidizing enzyme expression in Lentinula edodes by the addition of sawdust extract, aromatic compounds, or copper in liquid culture media.

This study examined how the addition of a sawdust extract from Castanopsis cuspidata, several aromatic compounds, and copper affected the expression of a phenol-oxidizing enzyme in the white-rot basidiomycete, Lentinula edodes. Compared to liquid media that had not been supplemented with sawdust extract (MYPG), MYPG containing low (MYPG-S100) or high (MYPG-S500) concentrations of sawdust extract had a marked effect on the promotion of mycelial growth. No manganese peroxidase (MnP) production was observed in either MYPG or MYPG-S100 media until 35 days after inoculation. However, MnP production was enhanced by culture in MYPG-S500, with a marked increase observed suddenly at 14 days after inoculation. Northern blot analysis revealed that the transcription of the lemnp2 gene coding extracellular MnP was initially observed at detectable levels at day 10 after the initial inoculation of MYPG-S500, increasing gradually thereafter until days 22-25. However, laccase (Lcc) production was not observed in any of the media until 35 days after inoculation. Addition of 10 mM aromatic compounds - 1,2-benzenediol, 2-methoxyphenol, hydroquinone, and 4-anisidine--into the MYPG-S500 medium completely inhibited MnP production and did not enhance any Lcc production. While the addition of 1 or 2 mM Cu2+ (CuSO4 x 5H2O) to MYPG-S500 medium completely inhibited MnP production, this Cu2+ addition caused a marked increase in Lcc production at 17 and 6 days after the addition, respectively.

Construction and validation of metagenomic DNA libraries from landfarm soil microorganisms.

Landfarming biodegradation is a strategy used by the petrochemical industry to reduce pollutants in petroleum-contaminated soil. We constructed 2 metagenomic libraries from landfarming soil in order to determine the pathway used for mineralization of benzene and to examine protein expression of the bacteria in these soils. The DNA of landfarm soil, collected from Ilhéus, BA, Brazil, was extracted and a metagenomic library was constructed with the Copy Control(TM) Fosmid Library Production Kit, which clones 25-45-kb DNA fragments. The clones were selected for their ability to express enzymes capable of cleaving aromatic compounds. These clones were grown in Luria-Bertani broth plus L-arabinose, benzene, and chloramphenicol as induction substances; they were tested for activity in the catechol cleavage pathway, an intermediate step in benzene degradation. Nine clones were positive for ortho-cleavage and one was positive for meta-cleavage. Protein band patterns determined by SDS-polyacrylamide gel electrophoresis differed in bacteria grown on induced versus non-induced media (Luria-Bertani broth). We concluded that the DNA of landfarm soil is an important source of genes involved in mineralization of xenobiotic compounds, which are common in gasoline and oil spills. Metagenomic library allows identification of non-culturable microorganisms that have potential in the bioremediation of contaminated sites.

Oil-bioremediation potential of two hydrocarbonoclastic, diazotrophic Marinobacter strains from hypersaline areas along the Arabian Gulf coasts.

Two halophilic, hydrocarbonoclastics bacteria, Marinobacter sedimentarum and M. flavimaris, with diazotrophic potential occured in hypersaline waters and soils in southern and northern coasts of Kuwait. Their numbers were in the magnitude of 10(3) colony forming units g(-1). The ambient salinity in the hypersaline environments was between 3.2 and 3.5 M NaCl. The partial 16S rRNA gene sequences of the two strains showed, respectively, 99 and 100% similarities to the sequences in the GenBank. The two strains failed to grow in the absence of NaCl, exhibited best growth and hydrocarbon biodegradation in the presence of 1 to 1.5 M NaCl, and still grew and maintained their hydrocarbonoclastic activity at salinities up to 5 M NaCl. Both species utilized Tween 80, a wide range of individual aliphatic hydrocarbons (C9-C40) and the aromatics benzene, biphenyl, phenanthrene, anthracene and naphthalene as sole sources of carbon and energy. Experimental evidence was provided for their nitrogen-fixation potential. The two halophilic Marinobacter strains successfully mineralized crude oil in nutrient media as well as in hypersaline soil and water microcosms without the use of any nitrogen fertilizers.

Tactic responses to pollutants and their potential to increase biodegradation efficiency.

A significant number of bacterial strains are able to use toxic aromatic hydrocarbons as carbon and energy sources. In a number of cases, the evolution of the corresponding degradation pathway was accompanied by the evolution of tactic behaviours either towards or away from these toxic carbon sources. Reports are reviewed which show that a chemoattraction to heterogeneously distributed aromatic pollutants increases the bioavailability of these compounds and their biodegradation efficiency. An extreme form of chemoattraction towards aromatic pollutants, termed 'hyperchemotaxis', was described for Pseudomonas putida DOT-T1E, which is based on the action of the plasmid-encoded McpT chemoreceptor. Cells with this phenotype were found of being able to approach and of establishing contact with undiluted crude oil samples. Although close McpT homologues are found on other degradation plasmids, the sequence of their ligand-binding domains does not share significant similarity with that of NahY, the other characterized chemoreceptor for aromatic hydrocarbons. This may suggest the existence of at least two families of chemoreceptors for aromatic pollutants. The use of receptor chimers comprising the ligand-binding region of McpT for biosensing purposes is discussed.

Biodegradation of alkyl derivatives of aromatic hydrocarbons and cell surface properties of a strain of Pseudomonas stutzeri.

Pseudomonas stutzeri strain 9 was isolated from petroleum-contaminated soil. The main purpose of this study was to investigate how the long-term contact of this strain with diesel oil influences its surface and biodegradation properties. The experiments showed that the tested strain was able to degrade aromatic alkyl derivatives (butylbenzene, sec-butylbenzene, tert-butylbenzene and isobutylbenzene) and that the storage conditions had an influence on the cell surface properties. Also greater agglomeration of the cells was observed in the scanning electron microscope (SEM) micrographs and confirmed in particle size distribution results. The results also indicated that the addition of rhamnolipids to the hydrocarbons led to modification of the surface properties of P. stutzeri strain 9, which could be observed in the zeta potential and hydrophobicity values.