Phytoremediation of mercury in pristine and crude oil contaminated soils: Contributions of rhizobacteria and their host plants to mercury removal

• Published in: Ecotoxicology and environmental safety Vol. 73; no. 8; pp. 1998 - 2003
• Main Authors: Sorkhoh, N.A., Ali, N., Al-Awadhi, H., Dashti, N., Al-Mailem, D.M., Eliyas, M., Radwan, S.S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-11-2010
• Subjects: Arthrobacter; Bacteria; Bacteria - classification; Bacteria - growth & development; Bacteria - metabolism; Biodegradation, Environmental; Brevibacillus brevis; Broad beans; Citrobacter freundii; Consortia; Crops; Crude oil; Cucumis sativus; Enterobacter aerogenes; Equivalence; Flavobacterium psychrophilum; Fullerenes; Genes, Bacterial; Lycopersicon esculentum; Mercuric Chloride - isolation & purification; Mercuric Chloride - metabolism; Mercuric Chloride - toxicity; Mercury; Mercury - isolation & purification; Mercury - metabolism; Mercury - toxicity; Micrococcus luteus; Nitrogen Fixation - physiology; Nitrogen-fixation; Oil-attenuation; Petroleum; Phaseolus vulgaris; Phytoremediation; Pisum sativum; Pseudomonas veronii; Rhizobacteria; Rhizobium - genetics; Rhizobium - metabolism; RNA, Ribosomal, 16S - genetics; Soil Microbiology; Soil Pollutants - isolation & purification; Soil Pollutants - metabolism; Soil Pollutants - toxicity; Soils; Vicia faba; Oil-attenuation; Rhizobacteria; Nitrogen-fixation; Mercury; Phytoremediation
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2010.08.033

The rhizospheric soils of three tested legume crops: broad beans (
Vicia faba), beans (
Phaseolus vulgaris) and pea (
Pisum sativum), and two nonlegume crops: cucumber (
Cucumis sativus) and tomato, (
Lycopersicon esculentum) contained considerable numbers (the magnitude of 10
5
g
−1 soil) of bacteria with the combined potential for hydrocarbon-utilization and mercury-resistance. Sequencing of the 16S rRNA coding genes of rhizobacteria associated with broad beans revealed that they were affiliated to
Citrobacter freundii,
Enterobacter aerogenes,
Exiquobacterium aurantiacum,
Pseudomonas veronii,
Micrococcus luteus,
Brevibacillus brevis,
Arthrobacter sp. and
Flavobacterium psychrophilum. These rhizobacteria were also diazotrophic, i.e. capable of N
2 fixation, which makes them self-sufficient regarding their nitrogen nutrition and thus suitable remediation agents in nitrogen-poor soils, such as the oily desert soil. The crude oil attenuation potential of the individual rhizobacteria was inhibited by HgCl
2, but about 50% or more of this potential was still maintained in the presence of up to 40
mg
l
−1 HgCl
2. Rhizobacteria-free plants removed amounts of mercury from the surrounding media almost equivalent to those removed by the rhizospheric bacterial consortia in the absence of the plants. It was concluded that both the collector plants and their rhizospheric bacterial consortia contributed equivalently to mercury removal from soil.