title: Metal-tolerant PAH-degrading bacteria: development of suitable test medium and effect of cadmium and its availability on PAH biodegradation.
abstract: The use of metal-tolerant polyaromatic hydrocarbon (PAH)-degrading bacteria is viable for mitigating metal inhibition of organic compound biodegradation in the remediation of mixed contaminated sites. Many microbial growth media used for toxicity testing contain high concentrations of metal-binding components such as phosphates that can reduce solution-phase metal concentrations thereby underestimate the real toxicity. In this study, we isolated two PAHs-degrading bacterial consortia from long-term mixed contaminated soils. We have developed a new mineral medium by optimising the concentrations of medium components to allow the bacterial growth and at the same time maintain high bioavailable metal (Cd(2+) as a model metal) in the medium. This medium has more than 60 % Cd as Cd(2+) at pH 6.5 as measured by an ion selective electrode and visual MINTEQ model. The Cd-tolerant patterns of the consortia were tested and minimum inhibitory concentration (MIC) derived. The consortium-5 had the highest MIC of 5 mg l(-1) Cd followed by consortium-9. Both cultures were able to completely metabolise 200 mg l(-1) phenanthrene in less than 4 days in the presence of 5 mg l(-1) Cd. The isolated metal-tolerant PAH-degrading bacterial cultures have great potential for bioremediation of mixed contaminated soils.
authors.affiliation: Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia, Mawson Lakes, SA, 5095, Australia.
authors.forename: Palanisami
authors.initials: P
authors.lastname: Thavamani
authors.forename: Mallavarapu
authors.initials: M
authors.lastname: Megharaj
authors.forename: Ravi
authors.initials: R
authors.lastname: Naidu
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D004785:Environmental Pollutants / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D019216:Metals, Heavy / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry / Q000378:metabolism*; D012989:Soil Pollutants / Q000032:analysis
chemical_list: D004785:Environmental Pollutants; D019216:Metals, Heavy; D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants; D002104:Cadmium