一株深海热液环境来源的PAHs降解菌TVG9-Ⅶ的系统发育与降解基因

Phylogenetic and degrading genes analysis of a PAHdegrading bacterium TVG9-Ⅶ from deep-sea hydrythermal environment

摘要:

摘要:【目的】对一株深海热液环境来源的多环芳烃(PAHs) 降解菌进行系统发育分析并对其降解特性和降解机制进行研究。【方法】对16S rRNA 基因进行扩增和测序，进行基于16S rRNA 基因序列的系统发育分析;利用GC-MS 测定其对PAHs 的降解率;通过构建基因组Fosmid 文库，克隆PAHs 降解基因簇;并利用RTPCR和qPCR 研究关键降解酶基因在不同PAHs 诱导下的表达情况。【结果】从西南太平洋劳盆地热液沉积物中分离到一株PAHs 降解菌株TVG9-Ⅶ，系统发育分析结果表明，该菌株属于

关键词:关键词: 深海热液区，新鞘氨醇杆菌，多环芳烃，降解基因簇，双加氧酶

Abstract:

Abstract:［Objective］ The aim of this study is to identify a polycyclic aromatic hydrocarbons (PAHs)-degrading bacterium isolated from deep-sea hydrothermal environment， including its taxonomy， characteristics and mechanism involved in PAH degradation ［Methods］ The phylogeny was studied by 16S rRNA gene clone，and the degradation rates against different PAHs were determined by GC-MS． Meanwhile，PAH-degrading gene cluster was cloned by the genomic Fosmid library construction; the function of the key degrading-gene expression was examined by RT-PCR and qPCR to observe gene expression in the response to different PAHs． ［Results］A PAH-degrading strain TVG9-Ⅶ was isolated from the hydrothermal chimney sample of the Lau basin in Southwest Pacific Ocean．It showed 99. 7% similarities with 16S rRNA gene of Novosphingobium indicum strain H25T ． The degradation rates of this strain against phenanthrene，fluoranthene and pyrene were 95．2%，57.3% and 69. 6% in 21 days，respectively．A gene cluster，containing PAHs initial dioxygenase genes pheA1a and pheA1b，was obtained from genomic fosmid library，with the insertion size of 12.522 kb．The gene pheA1a was enhanced by 4. 2 folds in mRNA expression in presence of phenanthrene，but expression enhancement was not observed in other tested PAHs including naphthalene，pyrene and fluoranthene．［Conclusion］ Strain TVG9-Ⅶ is isolated from deep-sea hydrothermal environment in genus Novosphingobium． It can degrade many kinds of PAHs，especially the high-weight-molecular PAHs．

Key words:Keywords: deep-sea hydrothermal field，Novosphingobium，polycyclic aromatic hydrocarbons，degradation gene cluster，dioxygenase