A Novel Pseudomonas Gessardii Strain LZ-E Simultaneously Degrades Naphthalene And Reduces Hexavalent Chromium

Combined pollutants with polycyclic aromatic hydrocarbons（PAHs） and heavy metals have been identified as toxic and unmanageable contaminates. In this work, Pseudomonas gessardii strain LZ-E isolated from wastewater discharge site of a petrochemical company degrades naphthalene and reduces Cr（VI） simultaneously. 95% of 10 mg L^-1 Cr（VI） was reduced to Cr（III） while 77% of 800 mg L^-1 naphthalene was degraded when strain LZ-E was incubated in BH medium for 48 h. According to LZ-E?s genome, naphthalene was degraded by naphthalene two operons encoding two pathways which can degrade naphthalene to salicylic acid and to acetyl-Co A. Furthermore, naphthalene promotes Cr（VI） reduction in strain LZ-E as catechol and phthalic acid produced in naphthalene degradation are able to reduce Cr（VI） abiotically. An aerated bioreactor system was setup to test strain LZ-E?s remediation ability. Strain LZ-E continuously remediated naphthalene and Cr（VI） at rates of 15 mg L^-1 h-1 and 0.20 mg L^-1 h-1of 800 mg L^-1 naphthalene and 10 mg L^-1 Cr（VI） addition with eight batches in 16 days. A native plasmid named p HWL10 with its length 8083 bp was found in strain LZ-E, there are three open reading frames which encode Rolling cycle replication protein（Rep）, Zonualr occludens toxin protein（Zot）, TypeII secretion protein（T2S）. The naphthalene degradation and chromate reduction ability of plasmid cured strain had little change revealed that plasmid might involve survival ability of strain LZ-E. In summary, strain LZ-E is a potential applicant for combined pollution remediation.