PAHs降解细菌在根表的成膜作用及其对植物吸收PAHs的影响

Anthropogenic soil contamination has become a worldwide environmental problem in recent decades. Organic pollutants present in soil may be taken up by plants and translocated into shoots, which is the major pathway for toxic organic substances to reach the food chain. Because plants form the basis of human and animal food chains, potentially harmful organic contaminants could find their way into human and animal populations via this route. Clearly, increased understanding of how plants take up organic contaminants from the soil could have considerable benefit for risk assessments. .Rhizobacteria usually form biofilms on root surfaces, protecting plants from external harsh environments or promoting plant growth. However, there is still limited information available on the biofilm-influenced uptake of organic contaminants by plants. As known, polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic contaminants commonly found in the soil environment. Due to their highly mutagenic and carcinogenic properties, considerable interest in uptake of PAHs by plants has emerged in recent decades. Several species of PAH-degrading bacteria (PAHDB) have been isolated from the environment. Unfortunately, Few literatures are available heretofore on the formation of the PAHDB-based biofilms associated with roots in rhizosphere, as well as the biofilm-influenced uptake of PAHs by plants. .To this end, this project seeks to (1) investigate the bacterial communities of root-associated biofilms under PAH-polluted condition, and isolate and identify the PAHDB with the ability of biofilm formation. (2) eludate the formation of PAHDB-based biofilms associated with roots. (3) clarify the impacts and mechanisms of PAHDB-based biofilms on the uptake of PAHs by plants. Basing on the sorption and degradation of PAHs on PAHDB-based biofilms, as well as the enzyme activities in rhizosphere and inner plants, the mechanisms of the biofilm-influenced uptake of PAHs by plants will be systematically elucidated. We think that this project will hopefully propose a biofilm-aided technique to eliminate plant PAH contamination in polluted soils. Results of this work would benefit agriculture production, food safety, and human and ecological health in PAH-contaminated sites.

植物可通过根系吸收有机污染物，而很多根际细菌可通过成膜作用在根表形成细菌生物膜，协助植物抵抗外界的不良环境或促进植物生长。根际有机污染物降解细菌在根表的成膜作用对植物吸收有机污染物有何影响？近来，该领域研究引起了学者重视，但相关报道还很少。本项目拟以多环芳烃（PAHs）为目标污染物，从污染区植物根表分离、筛选具有PAHs降解功能的成膜细菌（即功能细菌），明确其种群特性，研究其在根表的定殖性能、成膜作用以及对植物生长的影响；探讨根表功能细菌成膜作用对植物吸收PAHs的影响；分析根表功能细菌生物膜对PAHs的吸持和降解作用，弄清根际和植物体内PAHs代谢相关酶系的响应，系统地阐明根表功能细菌成膜作用影响植物吸收 PAHs的机理。综合地分析利用根表功能细菌生物膜调控植物吸收PAHs的可行性，试图为防治土壤有机污染、减低作物污染风险、保障农产品安全等提供理论依据。

近些年来，植物根表细菌生物膜的环境效应很受关注；但至今，关于多环芳烃（polycyclic aromatic hydrocarbons, PAHs）等持久性有机污染物降解细菌在植物根表的成膜作用以及其对植物吸收代谢PAHs的影响，国内外尚不清楚。基于此，本项目系统开展了相关研究，并取得了以下主要研究结果：（1）利用PCR-DGGE（Polymerase chain reaction-denaturing gradient gel electrophoresis technology）技术探究了自然条件下不同PAHs污染强度下植物根表细菌生物膜的群落结构特征，明确了PAHs污染条件下的植物根表优势种群，并分析了根表细菌生物膜种群对PAHs污染的响应。（2）利用富集培养和划线纯化等方法，从PAHs污染区健康植物根表分离筛选出多株以菲、芘等PAHs为唯一碳源生长的根表成膜细菌，并进一步研究了各成膜细菌对PAHs的降解能力，获得了可高效降解PAHs的功能细菌；在此基础上明确了各功能细菌的分类地位、生长条件和成膜能力，并对其降解PAHs的环境条件进行了优化。（3）利用温室盆栽实验，研究了各功能细菌在植物根表的成膜能力和分布情况，并分析了功能细菌在植物根表的成膜作用对植物生长以及吸收积累PAHs的影响，发现功能细菌在植物根表的成膜作用可有效减低植物体PAHs污染。（4）利用温室盆栽实验，明确了植物体内PAHs代谢相关酶系对功能细菌在植物根表定殖成膜的响应。.在此基础上，综合地分析了利用根表功能细菌生物膜调控植物吸收PAHs的可行性，提出利用根表细菌生物膜减低植物PAHs污染风险的新思路。研究成果可为发展作物PAHs污染防护技术、有效规避植物有机污染风险等提供思路和依据。依托本项目，发表论文11篇，其中在《Plant and Soil》、《Scientific Reports》、《PloS ONE》等刊物上发表SCI论文6篇，三篇论文发表在国际学科排名前10%期刊上；培养硕士研究生6名；申请国家发明专利2项。