Investigation of Microbes in the Rhizosphere of Selected Trees for the Rhizoremediation of Hydrocarbon-Contaminated Soils

Abstract

Hydrocarbon-degrading microorganisms (HDMs), associated with the rhizosphere of Conocarpus lancifolius and Ficus infectoria trees grown in bioremediated soil, were isolated under controlled laboratory conditions. The selected trees were used to phytoremediate oil-contaminated soil for three successive growing seasons. At the end of the phytoremediation experiment, 85.7% of measurable total petroleum hydrocarbon was degraded in the rhizosphere soil associated with Conocarpus lancifolius compared to 78.6% in the rhizosphere of Ficus infectoria. The detectable concentrations of some polyaromatic hydrocarbons were less than 0.02 ppm. The HDM isolation process was conducted at 35 degrees C under aerobic conditions. The isolated HDMs were identified using 16S rRNA gene sequencing and fatty acid methyl ester analysis. Differences in the genera of the isolated HDMs and their assessed efficiency in degrading a mixture of hydrocarbon compounds between the two trees were noted.

Potential for the Use of Rhizobacteria in the Sustainable Management of Contaminated Soils

“…Although some microorganisms can completely degrade a specific xenobiotic, individual species generally do not contain entire degradation pathways. Rather, microbial consortia in the rhizosphere work synergistically to effectively degrade the pollutants (Chaudhry et al 2005;Yateem et al 2007). For example, the synergistic degradation of naphthalene by two Pseudomonas fluorescens strains in the rhizosphere of a grass was reported by Bloemberg et al (2000).…”

Enhanced Hydrocarbons Degradation in the Rhizosphere of Mangrove Plants by a HalophilicBacillus Subtilis SubtilisStrain

“…Previous local studies proved that this HC mixture is an excellent enhancer for hydrocarbon degrading bacteria. (Al-Surrayai et al, 2009;Yateem et al, 2007;Yateem et al, 2008). Among the selected HC mixture, the compounds that were insoluble or have poor solubility in water were solubilized in acetone.…”

“…The potential role of hydrocarbon degrading microorganisms associated with the roots of plants vegetated in a polluted matrix in remediating contaminated environments merits systematic investigation. Several studies have identified many rhizospheric microorganisms that are capable of degrading hydrocarbons in polluted terrestrial environment (Kuiper et al, 2001;Radwan et al, 1998;Walton et al, 1994;Yateem et al, 2007;Yateem et al, 2008). In addition, a number of microorganisms that are capable of degrading hydrocarbon pollutants under the extreme conditions that exist in the marine environment were isolated from both sea and freshwater hydrocarbon-polluted sediments (Coates et al, 1997;Coates et al, 1996).…”

The Use ofConocarpus lancifoliusTrees for the Remediation of Oil-Contaminated Soils

“…It considers the use of trees with their physical and biological environment including the soil and associated microflora to treat and contain pollutants and prevent their spread by reducing their movements in contaminated soil and water (Komives and Gullner, 2006). The efficiency of dendroremediation has been proven in cleaning soils contaminated with crude oil, explosives, landfill leachates, metals, pesticides, polycyclic aromatic hydrocarbons (PAHs) and solvents (Yateem et al, 2008;Pilon-smits, 2005;Schoenmuth and Pestemer, 2004;Dietz and Schnoor, 2001;Macek et al, 2000). Trees have the advantage over grasses and other smaller plants, in that their roots grow deeper; therefore, they are used to reach deeper pollutions in the ground (EPA, 2001).…”