Isolation And Identification Of Naphthalene Degrading Bacteria And Characterization Of Their Degradation Pathways

Naphthalene and phenanthrene are typical representatives of polycyclic aromatic hydrocarbons (PAHs), which are often used as model compounds for research on PAHs bioremediation. Work on naphthalene and phenanthrene biodegradation can be valuable to understand the mechanism and feasibility of other PAHs, providing theorically and practically knowledge and control measurements to eliminate PAHs and petroleum hydrocarbons and other stubborn organic compounds of environmental pollution. Two naphthalene degrading bacteria were isolated from Zhang Gong dam of Jin Kou in Wuhan. The strains were identified their morphological, biochemical and physiological characteristics and their key genes involved in degradation pathway were also analyzed by PCR and sequencing. It was found that both strain XA1 and XB1 are all belonged to Pseudomonas fluorescens. In naphthalene medium their optimum growth temperature is 28 ℃ and their optimum growth pH are 7.5 and 7.0 respectively. The degradation of naphthalene achieved 93.4% and 74.7% after inoculated 3% of these bacteria culture into the inorganic salt medium containing 500 mg/L naphthalene for three days. In phenanthrene medium their optimum growth temperature is 28 ℃ and their optimum growth pH are 7.0 and 7.5 respectively. The degradation of phenanthrene was 75.1% and 64.8%, while their mix culture achieved 82.1%,after inoculated 10% of these bacteria culture into the inorganic salt medium containing 500 mg/L phenanthrene for seven days. Both the genome of the strain XA1 and XB1 encoded catechol 2,3-dioxygenase gene, which is recognized as necessary gene involved in naphthalene degradation.They can also degradate other PAHs such as fluorene, fluoranthene and pyrene and have a board degradation spectrum. The strain XA1 and XB1 showed great potential for remediation of PAHs-polluted environment due to their strong naphthalene and phenanthrene degrading ability.