Identification and characterization of an aerobic bacterium degrading chlorobenzene

Abstract:

Abstract: [Objective] To isolate and characterize aerobic bacteria to degrade effectively chlorobenzene (CB). [Methods] We used enrichment culture to isolate and characterized bacterial strain through the observation of morphological and biochemical characters and analysis of 16S rRNA gene sequences. We determined the concentration of CB, other chlorobenzenes and released Cl-, densities of strain cells and activities of catechol dioxygenase in crude extracts from cells in pure culture liquid. [Results] We isolated a bacterium able to effectively degrade CB and assigned as strain CB001.Phylogenetic analysis based on 16S rRNA gene showed the similarity of 98.5% between strain CB001 and Acinetobacter calcoaceticus. In pure culture with CB as the sole carbon and energy source, 98.2% of CB at initial concentration of 50 mg/L was degraded; the molar ratio of the amount of net released Cl- to the amount of CB degraded by strain CB001 ranged from 1:1.85 to 1:1.39; the average activity of catechol 1,2-dioxygenase in crude extracts was 0.538 U/mg protein. The addition of glucose increased significantly the density of cells and the concentration of net released Cl-, but decreased obviously the ability of per cell to degrade CB. The capacity of strain CB001 to degrade CB was inhibited in di-chlorobenzenes and tri-chlorobenzenes coexisting culture system. The order in which strain CB001 readily degraded di-chlorobenzenes was 1,3-dichlorobenzene >1,2-dichlorobenzene >1,4-dichlorobenzene. [Conclusion] The results showed that strain CB001 belonged to the genus Acinetobacter, which showed capacity to degrade CB, di-chlorobenzenes. Strain CB001 possibly degraded CB through the pathway of meta ring cleavage. The addition of CB in the culture liquid increased significantly the ability of strain CB001 to degrade CB and the activity of catechol 1,2-dioxygenase.

Key words:Keywords: Acinetobacter; phylogenetic analysis; chlorobenzene; catechol dioxygenase