Abstract

Soil bacteria play a major role in ecological and biodegradable function processes in oil-contaminated soils. Here, we assessed the bacterial diversity and changes therein in oil-contaminated soils exposed to different periods of oil pollution using 454 pyrosequencing of 16S rRNA genes. No less than 24,953 valid reads and 6246 operational taxonomic units (OTUs) were obtained from all five studied samples. OTU richness was relatively higher in contaminated soils than clean samples. Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Planctomycetes and Proteobacteria were the dominant phyla among all the soil samples. The heatmap plot depicted the relative percentage of each bacterial family within each sample and clustered five samples into two groups. For the samples, bacteria in the soils varied at different periods of oil exposure. The oil pollution exerted strong selective pressure to propagate many potentially petroleum degrading bacteria. Redundancy analysis (RDA) indicated that organic matter was the highest determinant factor for explaining the variations in community compositions. This suggests that compared to clean soils, oil-polluted soils support more diverse bacterial communities and soil bacterial community shifts were mainly controlled by organic matter and exposure time. These results provide some useful information for bioremediation of petroleum contaminated soil in the future.

Highlights

  • Crude oil is a complex mixture of hydrocarbons and other organic compounds that can bring up serious environmental problems when spills occur [1,2]

  • These pyrosequencing reads were clustered into operational taxonomic units (OTUs) [19]

  • The two clean soils harbored the highest water content and electric conductivity (EC) values among all samples (Table 1), meaning that some basic soil properties might have been changed by oil contamination and soil microbial activity

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Summary

Introduction

Crude oil is a complex mixture of hydrocarbons and other organic compounds that can bring up serious environmental problems when spills occur [1,2]. Pyrosequencing of 16S rRNA genes, developed by Roche 454 Life Science using sequencing-by-synthesis technology, is one of the popular high throughout sequencing systems and a powerful approach for investigating the bacterial communities in the environment [12,13]. This technology has been successfully used in analyzing microbial communities and diversity in various environmental samples, such as wastewater [10], biosolids [12], and oil-contaminated soil [14]. The purpose is to help us better understand the dynamics of bacterial communities in oil-contaminated soils and provide useful and appropriate information for bioremediation strategies of petroleum contaminated soil in the future

Study Site and Sample Treatment
DNA Extraction and PCR Amplification of Bacterial 16S rRNA Gene
High Throughput Sequencing of Bacterial 16S rRNA Gene
Statistical and Bioinformatics Analysis
Physicochemical Properties of Soil
Microbial Richness and Diversity
Taxonomic Composition
Relationships between Bacterial Communities among the Five Samples
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