[Isolation, identification and characterization of an atrazine degrading bacterium]

An atrazine-degrading bacterial strain named L-6 was isolated from the sludge mixture of the sewage treatment plant by cultivating in raw water with limited nutrition and aeration and was domesticated steadily using SBR (Sequencing Batch Reactor) for two months. The degradation rate of atrazine in inorganic liquid culture medium with atrazine as the sole source of nitrogen could reach 89.2% after 96 hours. The cells showed shape of long rod under scanning electron microscope. After extraction of genomic DNA and PCR amplification, the 16S rRNA gene sequences were used for homology analysis and construction of phylogenetic trees. The results suggested that the 16S rRNA gene sequence of L-6 had up to 99% homology with those of many strains of Pseudomonas strains in GenBank database. With physiological and biochemical reactions, the strain L-6 was identified as Pseudomonas sp. Carbon use test indicated that L-6 can utilize glucose, fructose and citric acid sodium as carbon sources, but could not use sucrose, lactose or starch. The optimum degradation conditions were optimized as following:temperature 30 degrees C, initial pH 7-9.