Toluene Biodegradation by Novel Bacteria Isolated from Polluted Soil Surrounding Car Body Repair and Spray Painting Workshops

Abstract

Toluene can enter the environment due to various industrial activities. Toluene exposure may cause serious health risks to human and other living organisms. Thus, removal of toluene from the environment is exceptionally important in toluene-contaminated habitats. The aim of present study was to isolate and characterize toluene-utilizing bacteria from contaminated soil surrounding car body repair and painting workshops in Irbid industrial city, Jordan. Therefore, polluted soil samples (10 g) were transferred to flasks containing 99 ml of Stanier’s medium supplemented with 1% toluene and aerobically incubated at 30°C for 72 h. Subsequently, four morphologically different toluene-utilizing bacteria, designated as T1, T2, T3, and T4, were isolated. The cells of T1, T2 and T3 were Gram-positive, rod-shaped, aerobic, and positive for oxidase and catalase. However, the cells of T4 were Gram-negative, round-shaped, aerobic, negative for oxidase, and positive for catalase. Based on 16S rDNA sequencing data, isolates T1, T2 and T3 had high homology (97% - 98%) with Lysinibacillus boronitolerans, Bacillus subtilis and Rhodococcus pyridinivorans, respectively, whereas the isolate T4 had a homology of 89% with Acinetobacter schindleri, and could represent a distinct lineage within the genus Acinetobacter. The generated 16S rDNA sequences were deposited in GenBank database. After testing different physicochemical conditions, the isolates appeared to grow best at 1% toluene, 30°C and pH 6.8, with the generation times ranged between 8 - 11 h. In conclusion, we reported for the first time the identification of four novel soil bacterial species with the capacity to utilize toluene as sole source of carbon and energy from soil sites surrounding car painting workshops. The beneficial effect of the four isolates in the bioremediation of toluene from toluene polluted soil areas must be examined under in situ and ex situ conditions.