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Ben-Gurion University of the Negev (2019)

Microbial biodegradation of aliphatic and aromatic hydrocarbons in arid soil contaminated by crude oil

Meshulam, Mor,

Titre : Microbial biodegradation of aliphatic and aromatic hydrocarbons in arid soil contaminated by crude oil

Auteur : Meshulam, Mor,

Etablissement de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science (MS) 2019

Résumé partiel
Accidental crude oil spills in the aquatic and terrestrial environments are common events with long-term adverse effects. Although of extremely slow rates, natural attenuation of the contaminating oil occurs through both abiotic (volatilization, photo- oxidation) and biotic (biodegradation) processes. The latest is the most significant mechanisms of oil mass reduction. From an ecological point of view, biodegradation, metabolizing of oil constituents by microorganisms, is an advantageous removal practice. Yet, biodegradation is often limited and in particularly in hot dry desert ecosystems due to the extreme environmental conditions of dryness, high temperatures, high solar radiation and nutrients poor soils. Bioremediation, cleaning of contaminated sites, can be achieved by several strategies depending on the nature of the contaminant and the contaminated environment. To accelerate contaminants biodegradation, practices such as microbial augmentation and/or on-site water content adjustment and nutrient amendments (such as nitrogen) to enhance the activity of the native microbial communities are common actions. This study has examined the effect of the crude oil spill on the microbial community structure and the possible emergence of oil degrading microbial species in the oil contaminated soil of Ein Evrona. in the southern Negev desert, Israel. Additionally, we examined the potential contribution of bio fertilization with soil bio-crust dwelling nitrogen fixing cyanobacteria (NFC), to the acceleration of crude oil biodegradation by providing bioavailable fixed inorganic nitrogen. Contaminated soil samples from the 2014 crude oil spill at the "Ein Evrona" natural reserve were examined in this study. Based on 16S rRNA gene sequences, ten dominant phyla were identified in the control soil samples and six dominant phyla in the pool and station 3 contaminated samples. Proteobacteria and Actinobacteria were found to be the most dominant Phyla in all three samples. Pool surface soil (where oil was contained during the spill event) showed high presence of Firmicutes, compared to the two other sites Calculated values of the Shannon Index of diversity were 5.44 in the control compared to 4.02 and 2.89 in the pool contaminated soil and the dry stream bed respectively. Furthermore, the three samples clustered differently from each other on PCA analysis. Three bacterial strains were isolated from the contaminated soil and identified as Pseudomonas spp. and Gordonia spp., both hold the metabolic ability for both aromatic and aliphatic degradation. Nitrogen-Fixing Cyanobacteria (NFC) enrichment cultures used for amendments in the slurry and microcosm experiments, showed 87.12% dominance of the Nostocophycideae class (based on Cyanobacteria-specific 16S rRNA gene fragment)

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