CHARACTERISATION OF A GENE FRAGMENT ENCODED DIOXYGENASE IN DIBENZOFURAN-DEGRADING BACTERIUM PAENIBAClLLUS SP. Ao3 ISOLATED FROM HERBICIDEfDIOXIN CONTAMINATED SOIL IN DANANG

Abstract

The dibenzofuran degrading bacterium A03 was isolated from pond mud in the herbicide/dioxin contaminated area in a former US military base at Danang Airport. Colony of A03 was cream white, round, slight convex and 1.5 - 3 mm diameter after 7 days of incubation in mineral salt medium containing dibenzofuran. Cells were rod shaped, with diameter ranging from 0.53 - 0.6 J-lm x 1.67 - 2.8 j.lm. 16S rDNA sequence analysis indicated that strain A03 was closely related to strains in genus Paenibacillus including Paenibacillus sp. HMI, Paenibacillus validus JCM9077, Paenibacillus naplhalenovorans DSM14203, Paenibacillus sp. YK5. Based on morphological characteristics and analysis of 16S rRNA gene sequence, A03 strain should be placed in genus Paenibacillus and named Paenibacillus sp. A03. The degenerate primer pair D10XY-F, DlOXY-R and total DNA of Ao3 strain were used for isolation a part of dioxygenase encoding gene. The nucleotide sequence of PCR product revealed that Ao3 carried the dioxygenase gene and had similar level of 93% to an ahDOa gene in Paenibacillus sp. YK5. However, the predicted amino acid sequence of dioxygenase gene product of Ao3 showed identical to ahDOa gene in Paenibacillus sp. YK5. In order to clarify the relationship between Ao3 and YK5, the DNA:DNA hybridisation and chemotaxonomy analysis as well as full nucleotide sequence of dioxygenase genes will be required.