质粒基因强化活性污泥系统对2,4–D的降解

以携带质粒pJP4含编码2,4-二氯苯氧基乙酸(2,4-D)降解功能的基因片段]的基因工程菌Pseudomonas putida SM1443::gfp2x (pJP4::dsRed)为供体菌,通过半连续流实验研究了质粒基因强化对活性污泥系统的2,4-D的降解效应及菌群结构的影响.结果表明,以初始浓度约为320mg/L的2,4-D为唯一碳源,向活性污泥系统投加携带pJP4质粒的基因工程菌P. putida,运行初期,降解促进作用不明显;随着半连续流反应的进行,促进作用显著增强.与对照系统相比,降解速率之差最高为6.67mg/(L·h).从基因强化系统中筛选到1株占有优势的接合子,经鉴定为Alcaligenes sp.::pJP4. Alcaligenes sp.本身不具备降解2,4-D的能力,获得质粒pJP4后,对2,4-D降解能力大幅度提高,与野生型2,4-D高效降解菌Bacillus sp.相当. PCR-DGGE分析表明,在受到2,4-D冲击条件下基因强化的活性污泥系统较对照系统保持了相对更加稳定的菌群结构.

Enhancing 2,4-D degradation in an activated sludge system through plasmid mediated gene-augmentation.

With plasmid pJP4 carrying genetic microorganism Pseudomonas putida SM1443::gfp2x (pJP4::dsRed) as the donor strain, which contains genetic elements encoding 2,4-dichlorophenoxyacetic acid (2,4-D) degradation on pJP4, plasmid mediated gene-augmentation was conducted in an activated sludge system operated in fed-batch runs. Effects of gene augmentation on 2,4-D degradation and system microbial community structure were investigated. Supplementation of pJP4 carrying genetic microorganism to an activated sludge system fed with 2,4-D as sole carbon source (initial concentration at 320 mg/L) could enhance 2,4-D degradation. This enhancement was only slight at the initial stage of the operation, but significantly increased with the increase in the operation time of fed-batch runs. The biggest difference in the 2,4-D average degradation rates between the gene-augmented system and its control was 6.67 mg/(L·h). One predominant transconjugant was isolated from the gene-augmented system and identified as Alcaligenes sp.::pJP4. Alcaligenes sp. itself failed to degrade 2,4-D, but demonstrated strong 2,4-D degradation ability after receiving plasmid pJP4, which was similar to a wild type 2,4-D degrading special bacteria Bacillus sp. PCR-DGGE analysis showed that gene-augmented activated sludge system maintained relatively more stable microbial community than the control system when facing 2,4-D shock loadings.