Isolation And Identification Of Phenol Degradating Bacteria From Salt Lakes And Their Phenol Degradating Characters

Microbial degradation of organic pollutants is a complex biochemical process that determined by many factors such as the activities of degradating enzymes as well as the adaptivity of microorganisms to their environment. There are plenty of microbial resources in the nature. They live in various environments and have vast genetic diversity. Isolation of the diverse pollutants degradating bacteria from natural environment and study on the correlation between the pollutant degrading activity and genetic characteristics of the microorganisms should be an effective way to reveal the key genetic character that determine the pollutant degradating capability of a microorganism. Present work aims to reveal the diversity of salt-tolerant phenol degradating bacteria in the natural saline environments and provide basis for the researches aims to understand the relationship between the genetic characters and phenol degrading activity.The samples were collected from Ejinoor salt lake, Jilantai salt lake and Chagannoor soda lake. It was found that consortium attained from Ejinoor salt lake after enrichment culture significantly reduce the concentration of phenol in the cultural medium. The microorganisms in the consortium were isolated by solid medium with phenol as the sole carbon source and two of the isolated microorganisms were identified by 16SrDNA method. The results showed that the two strains of phenol degrading bacteria belong to the genera of Propionibacterium and Halomonas. Degenerated primers of phenol monooxygenase gene, catechol 1,2 dioxygenase gene and catechol 2,3 dioxygenase gene were applied to the genome DNA of the two strain to detect the genes of key enzymes in the degradation process of phenol. Genes of phenol monooxygenase, catechol 1,2 dioxygenase were detected in the Propionibacterium species, indicating that the bacteria may first convert phenol into catechol and then convert catechol into muconic acid. Although the PCR conditions were optimized for many times, we failed to detect the genes of any degradating enzymes in the genome DNA of Halomonas, suggesting the gene sequence of the genes that encode phenol degradating enzyme might have large difference with the known sequences. Using the culture medium containing 200 mg/L of phenol and 10% mineral salt, the isolated strain was tested for the degradating activity of phenol. After one round of acclimation, the Propionibacterium species could degradate 98% of phenol in 7 days, and the Halomonas species degradate of phenol by 90% in 6 days. It was found that the 50mg/L yeast extract had no effect on the phenol degradation activity of the Propionibacterium species. However absence of yeast extract reduced the phenol degradating activity Halomonas species greatly.The present work is expected to make a contribution to understanding of the diversity of the salt tolerant phenol degrading bacteria in the natural environment.