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Molecular analysis of surfactant-driven microbial population shifts in hydrocarbon-contaminated soil.

ABSTRACT: We analyzed the impact of surfactant addition on hydrocarbon mineralization kinetics and the associated population shifts of hydrocarbon-degrading microorganisms in soil. A mixture of radiolabeled hexadecane and phenanthrene was added to batch soil vessels. Witconol SN70 (a nonionic, alcohol ethoxylate) was added in concentrations that bracketed the critical micelle concentration (CMC) in soil (CMC') (determined to be 13 mg g(-1)). Addition of the surfactant at a concentration below the CMC' (2 mg g(-1)) did not affect the mineralization rates of either hydrocarbon. However, when surfactant was added at a concentration approaching the CMC' (10 mg g(-1)), hexadecane mineralization was delayed and phenanthrene mineralization was completely inhibited. Addition of surfactant at concentrations above the CMC' (40 mg g(-1)) completely inhibited mineralization of both phenanthrene and hexadecane. Denaturing gradient gel electrophoresis of 16S rRNA gene segments showed that hydrocarbon amendment stimulated Rhodococcus and Nocardia populations that were displaced by Pseudomonas and Alcaligenes populations at elevated surfactant levels. Parallel cultivation studies revealed that the Rhodococcus population can utilize hexadecane and that the Pseudomonas and Alcaligenes populations can utilize both Witconol SN70 and hexadecane for growth. The results suggest that surfactant applications necessary to achieve the CMC alter the microbial populations responsible for hydrocarbon mineralization.

SUBMITTER: Colores GM

PROVIDER: S-EPMC92097 | biostudies-literature | 2000 Jul

REPOSITORIES: biostudies-literature

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Molecular analysis of surfactant-driven microbial population shifts in hydrocarbon-contaminated soil.

Colores G M GM Macur R E RE Ward D M DM Inskeep W P WP

Applied and environmental microbiology 20000701 7

We analyzed the impact of surfactant addition on hydrocarbon mineralization kinetics and the associated population shifts of hydrocarbon-degrading microorganisms in soil. A mixture of radiolabeled hexadecane and phenanthrene was added to batch soil vessels. Witconol SN70 (a nonionic, alcohol ethoxylate) was added in concentrations that bracketed the critical micelle concentration (CMC) in soil (CMC') (determined to be 13 mg g(-1)). Addition of the surfactant at a concentration below the CMC' (2 ...[more]

PMID: 10877792

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Project description:This study investigated the impacts of crude oil, diesel, and gasoline on the diversity of indigenous microbial communities as well as culturable microorganisms in the studied soil. Oil contamination led to shifts in the diversity of the soil's microbial communities, regardless of the contaminant applied. Unpolluted soils were more diverse and evenly distributed than contaminated samples. The domain Bacteria accounted for 65.15% of the whole microbial community. The bacterial phylum Proteobacteria dominated in all samples, followed by Actinobacteria and Acidobacteria. Pseudomonas with 28.15% of reads dominated in Proteobacteria, while Rhodococcus (3.07%) dominated in Actinobacteria, and Blastocatella (2.53%) dominated in Acidobacteria. The dominant fungal phyla across all samples were Ascomycota dominated by Penicillium (50.48% of sequences), and Zygomycota dominated by Mortierella (16.87%). Sequences similar to the archaeal phyla, Euryarchaeota and Thaumarchaeota, were also detected. The number of culturable microorganisms increased following the contamination and was higher in contaminated samples than in clean samples. Oil contamination also resulted in the enrichment of oil-degrading strains. Two bacteria, Serratia marcescens strain PL and Raoultella ornithinolytica PS, which were isolated from crude oil-contaminated soil, exhibited strong crude oil degradation ability. Strain PL was the most efficient strain and degraded 75.10% of crude oil, while strain PL degraded 65.48%, after 20 days of incubation. However, the mixed culture of the two strains was more effective than single strain and could achieve up to 96.83% of crude oil degradation, with a complete abatement of straight-chain hydrocarbons (from C12 to C25), and more than 91% removal of highly branched hydrocarbons, phytane and pristane, which are known to be more recalcitrant to biodegradation. Strains PS and PL are two newly isolated crude oil degraders that are not among the most prominent crude oil-degrading strains referenced in the literature. Therefore, their high degradation capacity makes them perfect candidates for the bioremediation of petroleum hydrocarbon contaminated environments.

Project description:Soil health deteriorates through the contamination and remediation processes, resulting in the limitation of the reuse and recycling of the remediated soils. Therefore, soil health should be recovered for the intended purposes of reuse and recycling. This study aimed to evaluate the applicability and effectiveness of several amendments to revitalize total petroleum hydrocarbon contaminated soils remediated by the landfarming process. Ten inorganic, organic, and biological amendments were investigated for their dosage and duration, and nine physicochemical, four fertility, and seven microbial (soil enzyme activity) factors were compared before and after the treatment of amendments. Finally, the extent of recovery was quantitatively estimated, and the significance of results was confirmed with statistical methods, such as simple regression and correlation analyses assisted by principal component analysis. The landfarming process is considered a somewhat environmentally friendly remediation technology to minimize the adverse effect on soil quality, but four soil properties-such as water holding capacity (WHC), exchangeable potassium (Ex. K), nitrate-nitrogen (NO3-N), available phosphorus (Av. P), and urease-were confirmed to deteriorate through the landfarming process. The WHC was better improved by organic agents, such as peat moss, biochar, and compost. Zeolite was evaluated as the most effective material for improving Ex. K content. The vermicompost showed the highest efficacy in recovering the NO3-N content of the remediated soil. Chlorella, vermicompost, and compost were investigated for their ability to enhance urease activity effectively. Although each additive showed different effectiveness according to different soil properties, their effect on overall soil properties should be considered for cost-effectiveness and practical implementation. Their overall effect was evaluated using statistical methods, and the results showed that compost, chlorella, and vermicompost were the most relevant amendments for rehabilitating the overall health of the remediated soil for the reuse and/or recycling of agricultural purposes. This study highlighted how to practically improve the health of remediated soils for the reuse and recycling of agricultural purposes.

Dataset Information

Molecular analysis of surfactant-driven microbial population shifts in hydrocarbon-contaminated soil.

Publications

Molecular analysis of surfactant-driven microbial population shifts in hydrocarbon-contaminated soil.

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