title: Bioremediation potential of a highly mercury resistant bacterial strain Sphingobium SA2 isolated from contaminated soil.
abstract: A mercury resistant bacterial strain, SA2, was isolated from soil contaminated with mercury. The 16S rRNA gene sequence of this isolate showed 99% sequence similarity to the genera Sphingobium and Sphingomonas of α-proteobacteria group. However, the isolate formed a distinct phyletic line with the genus Sphingobium suggesting the strain belongs to Sphingobium sp. Toxicity studies indicated resistance to high levels of mercury with estimated EC50 values 4.5 mg L(-1) and 44.15 mg L(-1) and MIC values 5.1 mg L(-1) and 48.48 mg L(-1) in minimal and rich media, respectively. The strain SA2 was able to volatilize mercury by producing mercuric reductase enzyme which makes it potential candidate for remediating mercury. ICP-QQQ-MS analysis of Hg supplemented culture solutions confirmed that almost 79% mercury in the culture suspension was volatilized in 6 h. A very small amount of mercury was observed to accumulate in cell pellets which was also evident according to ESEM-EDX analysis. The mercuric reductase gene merA was amplified and sequenced. The deduced amino acid sequence demonstrated sequence homology with α-proteobacteria and Ascomycota group.
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: Khandaker.mahbub@mymail.unisa.edu.au.
authors.forename: Khandaker Rayhan
authors.initials: KR
authors.lastname: Mahbub
authors.affiliation: Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: Kannan.krishnan@newcastle.edu.au.
authors.forename: Kannan
authors.initials: K
authors.lastname: Krishnan
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: megh.mallavarapu@newcastle.edu.au.
authors.forename: Mallavarapu
authors.initials: M
authors.lastname: Megharaj
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: ravi.naidu@crccare.com.
authors.forename: Ravi
authors.initials: R
authors.lastname: Naidu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001673:Biodegradation, Environmental; D008628:Mercury / Q000378:metabolism* / Q000633:toxicity; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012989:Soil Pollutants / Q000378:metabolism* / Q000633:toxicity; D042301:Sphingomonadaceae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D010088:Oxidoreductases; C021551:mercuric reductase; D008628:Mercury
keywords: Hg removal; Hg resistance; Hg volatilization; Mercury; Sphingobium