珠江口红树林细菌群落间的PAHs降解基因水平传递及影响机制

The microbes could increase their degradation ability by more pollutants degrading bacteria or achieving PAH degrading genes from the surroundings. PAH degrading genes has been discovered in the mangrove and their abundance and diversity are related to PAH concentration. Our investigation suggesting that the PAH degrading genes could transfer among bacterial communities by plasmids, and this would be an efficient approach to enhance the bacteria's PAH degrading ability. In order to reveal the mechanism, influence factors for PAH degrading genes' horizontal transfer, mangrove was chosen as the representative region. We focus on the gene type, abundance and horizontal transfer ability of PAH degrading genes carried by plasmids in mangrove sediments, and their relationship with PAH concentrations. The metagenomics will be chosen as major tool and simulating experiment for plasmid transformation will be conducted. By these efforts, we want to reveal the mechanism for environmental bacterial communities to adapt to contamination and improve their degrading ability, and finally provide the theory foundation for environmental remediation of PAHs.

污染胁迫下，细菌群落可以通过增加降解菌的种类及数量，从而提高对污染物的耐受或降解能力，其中包括非降解菌从周围环境获得降解基因。红树林细菌群落携带多种PAHs降解基因且丰度与PAHs污染程度存在正相关性。申请人通过前期研究发现PAHs降解基因通过质粒水平传递作用在不同的细菌群落之间的传递是细菌群落提高降解能力的方式之一。为了揭示PAHs降解基因水平传递的机制及影响因素，并且阐明降解基因的传递现象在环境中是否普遍存在。本项目选择珠江口红树林作为代表区域，采用宏基因组的手段，结合质粒转化模拟实验，研究红树林细菌群落中质粒携带的PAHs降解基因的种类、含量和水平传递能力，及其与PAHs污染程度的相关性。最终揭示实际环境中细菌群落适应污染物胁迫、提高降解能力的机制，为PAHs的污染治理提供理论基础。

微生物降解是环境中多环芳烃（PAHs）去除的重要途径，而其中发挥关键作用的是降解酶，而降解酶离不开降解基因的表达。因此对于PAHs降解基因的研究，有助于深入了解微生物对PAHs的降解机制。而环境中的降解基因并不是不成不变的，它们可能在环境因素的影响下发生种类和丰度的变化，其中包括污染的胁迫。另外降解基因也可能发生迁移，包括在环境中的位置的改变和不同细菌间的转移。其中位置改变可能与水流、颗粒物吸附等因素有关，而水平转移则可能借助质粒作为载体。因此本项目选择了珠江口作为研究区域，通过对PAHs降解基因的种类和分布的研究，探讨其在珠江口的环境行为。结果表明，PAHs降解基因不仅可以自由态随水流传输，还有一部分以颗粒物作为载体，珠江口内颗粒物上的PAHs降解基因丰度约占总丰度的65%。其中介导CAPs过程的降解基因比例最高，而介导SCPs过程的降级基因比例最低。另外，通过提取质粒测序证实了珠江口细菌质粒上存在降解基因，且PAHs胁迫有利于质粒上降解基因的保留。通过以上研究，初步了解了珠江口内PAHs降解基因的传输和转移行为，为PAHs的微生物治理提供了理论基础。