二噁英降解质粒参与的生物相与非生物相的粘附作用机制研究

二噁英是一类代表性持久性有机污染物，基于微生物降解的生物修复是去除环境中二噁英污染的重要途径。但受土壤中二噁英的生物可利用性、有效降解菌浓度等限制，土壤中二噁英污染的原位生物修复严重受阻。细菌的粘附作用与一系列重要生物学功能相关，包括表面吸附、聚集形成生物膜、细胞间吸附等；而降解菌在污染土壤基质表面的吸附、聚集，是改善持久性有机污染物的生物可利用性、提高降解菌群浓度的重要方式。目前关于降解微生物在污染环境介质表面的行为及作用模式的研究相对匮乏，缺乏对于降解质粒参与的粘附作用的相关研究。本项目拟以红球菌p52携带的二噁英降解质粒为研究对象，考察其参与合成的粘附素的理化性质，研究粘附素介导的非生物介质表面粘附、菌体聚集、细胞间粘附的作用机制。本研究可为持久性有机污染物的生物修复理论与技术提供借鉴。

Dioxins, including polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, are the typical representative of persistent organic pollutants (POPs). Remediation of the dioxins-polluted environment is urgent, and cleanup of the contaminants based on microbial degradation is preferred. However, the bioremediation is hampered due to the highly hydrophobic characteristic of the dioxins molecules. In dioxins-contaminated soils, dioxins are absorbed to the soil aggregate or even trapped in micropores, which reduces their bioavailability. The insufficient degrading-bacteria density in the microenvironment adjacent to the contaminants is also a determinant of the failure during bioremediation. In recent years, bacterial adhesins has attracted considerable research interests, which play important roles on bacteria attachment to surface, biofilm formation, and close contact of cells. As reported, bacteria adhesion to the contaminated soil and forming biofilms promoted the bioavailability of hydrophobic contaminants and enhanced the biodegradation. It seems that bacterial adhesins may provide clues for breaking the bottleneck of dioxins contamination bioremediation. Till now, there are a few studies on the behavior of degrading bacteria addressing their interaction with contaminated matrix surface. There is a lack of the study on catabolic plasmid-associated adhesions. We previously isolated a dioxin-degrader, Rhodococcus sp. strain p52. The strain has two conjugative dioxin-catabolic plasmids, pDF01 and pDF02. The proposed research will focus on the adhesive protein encoded by the catabolic plasmid or the adhesin in association with the plasmid-coding enzyme. The physiochemical properties of the adhesins will be characterized. And efforts will be made to examine the mechanisms addressing strain p52 adhesion to abiotic surfaces, cell aggregation into biofilms, and cell-to-cell contacts. The proposed study will broaden our knowledge to bioremediation of dioxins contaminated environment, and contribute to application in POPs pollution remediation.