Study on PAH degrading bacteria isolated from dioxin contaminated soil in Vietnam

Abstract

Bacterial community in dioxin contaminated soil and mud samples from Danang airport was enumerated and studied for their potential degradation capability against three-ring compound carbazol. The cell number was determined on nutrient rich medium and on mineral medium supplemented with carbazol. It has been showed that number of cells presented in mud samples was significantly higher than in soil samples, in the range of 1 magnitude order. About 50% of the total cell number in each sample grown on the medium with carbazol. Analyzing 12 representative strains selectively isolated on the carbazol containing medium by using the ARDRA method with two endonucleases HaeIII and MspI showed that bacterial community at the studied areas was highly diversified. However non from these isolates could degrade carbazol significantly. Via enrichment and isolation steps using carbazol as the only energy and carbon sources, two carbazol degrading isolates R03 and R05 were obtained. Phylogenetic analyses based on 16S rDNA sequences showed that these strains were most affiliated to Bacillus and Archromobacter species, the most closely related species were Achromobacter xylosoxydans (99% homology) and Bacillus subtilis (98% homology). These strains were therefore designated the names Bacillus sp. R03 and Achromobacter sp. R05.