Abstract
The study of microbial communities involved in soil bioremediation is important to identify the specific microbial characteristics that determine improved decontamination rates. Here, we characterized bacterial, archaeal, and fungal communities in terms of (i) abundance (using quantitative PCR) and (ii) taxonomic diversity and structure (using Illumina amplicon sequencing) during the bioremediation of long-term hydrocarbon-contaminated soil from an Alpine former military site during 15 weeks comparing biostimulation (inorganic NPK fertilization) vs. natural attenuation and considering the effect of temperature (10 vs. 20 °C). Although a considerable amount of total petroleum hydrocarbon (TPH) loss could be attributed to natural attenuation, significantly higher TPH removal rates were obtained with NPK fertilization and at increased temperature, which were related to the stimulation of the activities of indigenous soil microorganisms. Changing structures of bacterial and fungal communities significantly explained shifts in TPH contents in both natural attenuation and biostimulation treatments at 10 and 20 °C. However, archaeal communities, in general, and changing abundances and diversities in bacterial and fungal communities did not play a decisive role on the effectiveness of soil bioremediation. Gammaproteobacteria and Bacteroidia classes, within bacterial community, and undescribed/novel groups, within fungal community, proved to be actively involved in TPH removal in natural attenuation and biostimulation at both temperatures.
Highlights
Many places around the world are impacted by petroleum hydrocarbon contamination as a consequence of anthropogenic activities such as industrial and municipal runoffs, effluent release, and offshore and onshore petroleum industry as well as accidental spills, which has become a major environmental concern (Brassington et al 2007; Gkorezis et al 2016)
Regardless of temperature, fertilization resulted in an increase in bacterial abundance compared to natural attenuation after 15 weeks
These findings, as well as those obtained for fungal community, concur with the data obtained through the PLFA-based analysis (Mair et al 2013), indicating that most of the microorganisms targeted through qPCR are living microorganisms (Blagodatskaya and Kuzyakov 2013)
Summary
Many places around the world are impacted by petroleum hydrocarbon contamination as a consequence of anthropogenic activities such as industrial and municipal runoffs, effluent release, and offshore and onshore petroleum industry as well as accidental spills, which has become a major environmental concern (Brassington et al 2007; Gkorezis et al 2016). Physical and chemical strategies, such as chemical inactivation, combusting, photolysis, soil vapor extraction, and soil washing, have been used as decontamination strategies for petroleum-polluted soils (Varjani 2017; Xu et al 2013). These methods are not economically viable and can involve significant site disturbances (Shahi et al 2016a). Bioremediation, taking advantage of the capacity of a wide range of microorganisms to use hydrocarbons as the sole source of carbon and energy (biodegradation), has shown to be a cost-effective and ecologically acceptable clean-up approach to treat hydrocarboncontaminated soils (Varjani 2017). Bioremediation treatments have been extensively applied for the decontamination of soils from an ample range of environments using laboratory or in situ approaches (Azubuike et al 2016; Margesin 2007; Appl Microbiol Biotechnol (2018) 102:4409–4421
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