Alkane utilization by Rhodococcus strain NTU-1 alone and in its natural association with Bacillus fusiformis L-1 and Ochrobactrum sp

Multispecies Diesel Fuel Biodegradation and Niche Formation Are Ignited by Pioneer Hydrocarbon-Utilizing Proteobacteria in a Soil Bacterial Consortium

A soil bacterial consortium that was grown on diesel fuel and consisted of more than 10 members from different genera was maintained through repetitive subculturing and was utilized as a practical model to investigate a bacterial community that was continuously exposed to petroleum hydrocarbons. Through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification which supported the linkage of genomic data and functionality, two pioneering genera, Sphingobium and Pseudomonas, whose catabolic capabilities were differentiated, were found to be responsible for the creation of specialized ecological niches that were apparently occupied by other bacterial members for survival within the consortium. Coexisting genera Achromobacter and Cupriavidus maintained their existence in the consortium through metabolic dependencies by utilizing hydrocarbon biotransformation products of pioneer metabolism, which was confirmed through growth tests and identification of biotransformation products of the isolated strains. Pioneering Sphingobium and Pseudomonas spp. utilized relatively water-insoluble hydrocarbon parent compounds and facilitated the development of a consortium community structure that resulted in the creation of niches in response to diesel fuel exposure which were created through the production of more-water-soluble biotransformation products available to cocolonizers. That these and other organisms were still present in the consortium after multiple transfers spanning 15 years provided evidence for these ecological niches. Member survival through occupation of these niches led to robustness of each group within the multispecies bacterial community. Overall, these results contribute to our understanding of the complex ecological relationships that may evolve during prokaryotic hydrocarbon pollutant biodegradation.IMPORTANCE There are few metagenome studies that have explored soil consortia maintained on a complex hydrocarbon substrate after the community interrelationships were formed. A soil bacterial consortium maintained on diesel fuel was utilized as a practical model to investigate bacterial community relationships through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification, which supported the linkage of genomic data and functionality. Two pioneering genera were responsible for the biodegradation of aromatics and alkanes by initiating biotransformation and thereby created specialized niches that were populated by other members. A model that represents these relationships was constructed, which contributes to our understanding of the complex ecological relationships that evolve during prokaryotic hydrocarbon pollutant biodegradation.

Multilevel changes in bacterial properties on long-term exposure to hydrocarbons and impact of these cells on fresh-water communities

To handle the impact of habitat transformations, the microbial cells developed mechanisms aimed at adjustment of their biological processes in response to signals indicating environmental changes. One of the first changes in their properties is observed on their surface, which has direct contact with the dynamically varying surroundings. In this study, we present results of changes in the cell surface properties which may have a decisive impact on the xenobiotics' bioavailability and microbial cell survival. These changes influence their ability to remove xenobiotics by accelerating and empowering this process. Moreover, the application of microorganisms exposed for long-term to hydrocarbons in bioremediation processes might have positive impact on biodegradation of the latter in the natural environment as well as natural microbial community diversity. This study demonstrates a variety of microbial cell mechanisms of adaptation to long-term exposure to hydrocarbons and their potential as the bioremediation tools.

Biodegradation of A-fuel oil in soil samples with bacterial mixtures of Rhodococcus and Gordonia strains under low temperature conditions

Bioaugmentation is an effective treatment to clean up polluted sites using contaminant-degrading bacteria. However, this treatment is influenced by various environmental conditions, including temperature. In this study, an effective bioaugmentation system under low temperature condition was developed with three Rhodococcus (strains A, C, and D) and one Gordonia (strain B) oil-degraders, which are officially permitted for bioaugmentation applications in Japan. The oil-degrading ability of each strain and mixture was assessed in liquid culture and in model soils supplemented with A-fuel oil. In liquid culture, Rhodococcus strains A and C degraded the A-fuel oil in cold temperature conditions (15°C and 10°C) as well as in mesophilic condition (30°C). In the model soil samples, the mixture of four degraders was the most effective at removing the A-fuel oil under mesophilic condition (>90%), suggesting that strains B and/or D might have factors that promote degradation. In contrast, A-fuel oil was efficiently removed (>80%) in the soil samples inoculated with A or C as well as that with mixture in cold temperature condition, suggesting that strains A and C were the major degraders under cold condition. Our results indicate that the four degraders could be applied to the bioaugmentation in cold areas.

Oil-degrading properties of a psychrotolerant bacterial strain, Rhodococcus sp. Y2-2, in liquid and soil media

The aim of this study was to investigate oil-degrading ability of newly isolated strain Rhodococcus Y2-2 at low temperature. Rhodococcus sp. Y2-2 was isolated from oil-contaminated soil sampled at the end of winter using a newly developed transwell plate method. In the liquid phase, the oil-degradation efficiency of strain Rhodococcus sp. Y2-2 was about 84% with an initial concentration of 1500 ppm TPH (500 ppm each of kerosene, gasoline, and diesel) when incubated for 2 weeks under optimal conditions: 10 °C, pH 7, and 0.5 g L^- 1 inoculum. In the soil phase, the isolate showed 80% oil degradation efficiency using glucose as a carbon source, with an initial concentration of 4000 ppm TPH and the addition of water during 14 days of incubation at 10 °C. Additionally, the degradation efficiency of the isolate was increased by the addition of mixture of surfactant alpha olefin sulfonate and gelatin, although strain Y2-2 also produced many biosurfactant components. This study shows Rhodococcus sp. Y2-2 can degrade oil components both in liquid and soil media by consuming kerosene, gasoline, and diesel as a carbon and energy source. Therefore, the crude oil-degrading ability of Rhodococcus sp. Y2-2 at low temperature provides proper bioremediation tool to clean up oil-contaminated sites especially in cold area or during winter season.

Removal of cyclohexane gaseous emissions using a biotrickling filter system

The removal of cyclohexane from gaseous emissions was studied using a biotrickling filter packed with polyurethane foam. Acivodorax sp. CHX100 was chosen as inoculum due to its ability to use cyclohexane as carbon source. Performance was evaluated by means of different resident times from 18 s to 37 s and concentration levels of 60, 90, 120, 160, 320, 480 and 720 mg C m^-3, respectively. Removal efficiencies of 80%-99% and elimination capacities in the range of 5.4 g C m^-3 h^-1-38 g C m^-3 h^-1 were achieved for concentrations among 60 mg C m^-3-480 mg C m^-3. The removal efficiency decreased to 40% at concentrations of cyclohexane of 720 mg C m^-3. The dynamics of the microbial population showed the strain CHX100 as predominant during the different operational process of biotrickling filter. The results of this study propose a novel approach for cleaning waste air containing cyclohexane by means of a biotrickling filter.

Characterization of a Novel Polymeric Bioflocculant Produced from Bacterial Utilization of n-Hexadecane and Its Application in Removal of Heavy Metals

A novel polymeric bioflocculant was produced by a bacterium utilizing degradation of n-hexadecane as the energy source. The bioflocculant was produced with a bioflocculating activity of 87.8%. The hydrocarbon degradation was confirmed by gas chromatography-mass spectrometry analysis and was further supported with contact angle measurements for the changes in hydrophobic nature of the culture medium. A specific aerobic degradation pathway followed by the bacterium during the bioflocculant production and hydrocarbon utilization process has been proposed. FT-IR, SEM-EDX, LC/MS, and ¹H NMR measurements indicated the presence of carbohydrates and proteins as the major components of the bioflocculant. The bioflocculant was characterized for its carbohydrate monomer constituents and its practical applicability was established for removing the heavy metals (Ni²⁺, Zn²⁺, Cd²⁺, Cu²⁺, and Pb²⁺) from aqueous solutions at concentrations of 1–50 mg L^-1. The highest activity of the bioflocculant was observed with Ni²⁺ with 79.29 ± 0.12% bioflocculation efficiency.

Production of a non-cytotoxic bioflocculant by a bacterium utilizing a petroleum hydrocarbon source and its application in heavy metal removal

A bacterium isolated from the activated sludge of an oil refinery of Assam, India retained efficient bioflocculating activity through production of the bioflocculant when it was grown on a crude oil amended medium void of any other carbon source.

Degradation of recalcitrant aliphatic and aromatic hydrocarbons by a dioxin-degrader Rhodococcus sp. strain p52

This study investigates the ability of Rhodococcus sp. strain p52, a dioxin degrader, to biodegrade petroleum hydrocarbons. Strain p52 can use linear alkanes (tetradecane, tetracosane, and dotriacontane), branched alkane (pristane), and aromatic hydrocarbons (naphthalene and phenanthrene) as sole carbon and energy sources. Specifically, the strain removes 85.7 % of tetradecane within 48 h at a degradation rate of 3.8 mg h(-1) g(-1) dry cells, and 79.4 % of tetracosane, 66.4 % of dotriacontane, and 63.9 % of pristane within 9-11 days at degradation rates of 20.5, 14.7, and 20.3 mg day(-1) g(-1) dry cells, respectively. Moreover, strain p52 consumes 100 % naphthalene and 55.3 % phenanthrene within 9-11 days at respective degradation rates of 16 and 12.9 mg day(-1) g(-1) dry cells. Metabolites of the petroleum hydrocarbons by strain p52 were analyzed. Genes encoding alkane-hydroxylating enzymes, including cytochrome P450 (CYP450) enzyme (CYP185) and two alkane-1-monooxygenases, were amplified by polymerase chain reaction. The transcriptional activities of these genes in the presence of petroleum hydrocarbons were detected by reverse transcription-polymerase chain reaction. The results revealed potential of strain p52 to degrade petroleum hydrocarbons.

Application of bioflocculating property of Pseudomonas aeruginosa strain IASST201 in treatment of oil-field formation water

A bioflocculating activity of 89.8% was depicted by an activated sludge-borne bacteria Pseudomonas aeruginosa strain IASST201 with a yield of bioflocculant of 2.68 g L(-1) obtained from production media broth after optimization of different parameters. The highest bioflocculation efficiency was found at the pre-stationary phase of the bacterial growth period in the production media broth at 96th hour examined from a growth-flocculation kinetics study. 85.67% of bioflocculation was observed in oil-field formation water, with a separation of 68.7% of aliphatic hydrocarbon contents of the formation water after the application of the bacterial bioflocculant by entrapment mechanism with formation of flocs which was analyzed and examined comparatively through gas-chromatography. Extensive removal of heavy metal contents of the oil-field formation water due to bioflocculation was estimated by Atomic Absorption Spectrophotometer (AAS). The SEM and AFM studies declare the extracellular polymeric nature of the bioflocculant produced by this bacterium clumped within bacterial biofilm supported with FTIR study of the extracted bioflocculant.