嗜盐菌群对菲的降解及萘双加氧酶基因的表达规律

Phenanthrene biodegradation and dynamic change of expression of naphthalene dioxygenase(ndo) genes in a halophilic bacteria consortium

从胜利油田富集了一个能够降解多环芳烃的嗜盐菌群,通过克隆文库技术解析了菌群萘双加氧酶(ndo)基因的多样性.结果表明,该嗜盐菌群有6种ndo基因型,其中3种主要基因型(占总克隆子92.7%)与经典nah-like基因的相似度为89%.采用real-time RT-PCR等技术分析了不同盐度下菲降解过程中ndo基因的表达量、降解速率、生长曲线以及菲的生物可利用度,探索了菌群对菲的降解及ndo基因的表达规律.结果表明,当盐度由10%升高到20%,菌群完全降解100mg/L菲的时间从6d延长到9d,菌群生长的迟滞期由1d延长为3d.溶解菲的浓度在菌群生长过程中呈增加的趋势.Ndo基因的表达量在降解过程中呈先降低后随溶解菲浓度升高而升高的趋势,表明高浓度菲在初始阶段可能抑制ndo基因的表达.单因素方差分析(n=3,P>0.05)表明溶解菲浓度在10%和20%盐度下没有显著差异,表明一定范围的盐度不会影响菌群降解过程中菲的溶解度.菌群ndo基因的相对表达量在10%盐度下较在20%盐度下高,说明盐度对嗜盐菌群功能基因的表达具有抑制作用.

A halophilic bacterial consortium capable of degrading phenanthrene was developed from Shengli Oilfield in China. The diversity of naphthalene dioxygenase （ndo） genes in the bacterial consortium was analyzed by the method of clone library. Consortium consist of six nah-like genes. Three of them （covered 92.7% of the total clones） related to the classic nah-like genes with identity of about 89%. Using real-time reverse transcription PCR and other techniques, this study investigated the dynamic expression of ndo genes, biodegradation rate, biomass and bioavailability of phenanthrene in bacterial consortium growing at different salinities. As the salinity increased from 10% to 20%, the lag phase increased from 1 day to 3 days, the time needed for degrading 100mg/L phenanthrene increased from 6 days to 9 days. Both of the dissolved phenanthrene concentrations at 10% and 20% salinity increased constantly during the biodegradation, and One-way ANOVA（n=3, P〉0.05） analysis showed there were no significant difference between them. A certain range of salinity probably not affected the bioavailability of phenanthrene. The expression of ndo genes at 20% salinity was lower than that at 10% salinity, while both of them decreased at the lag phase, and then increased constantly. Increasing salinity and high concentration of phenanthrene inhibited the expression of ndo genes.