卤代芳烃代谢质粒pBHB与宿主Comamonas sp. 7D-2的补偿性进化机制

代谢型质粒进化是细菌适应污染环境的重要机制，但是质粒复制、接合转移以及基因表达等生理活动会给宿主带来相应的生理负担。因此，质粒往往通过与宿主的补偿性进化来降低宿主负担，提高质粒在宿主菌群中的稳定性和传播性。然而，代谢型质粒与宿主的补偿性进化机制研究十分匮乏，制约了质粒介导的有机污染物微生物强化修复技术的应用。本项目以IncP-1β亚群的卤代芳烃代谢质粒pBHB和宿主Comamonas sp. 7D-2为研究对象，以3,5-二溴-4-羟基苯甲酸为选择压力，开展质粒与宿主的共进化研究，评估质粒与宿主的适应性，揭示质粒基因丢失、代谢基因簇表达的紧缩调控、质粒和宿主染色体核心基因的补偿性突变对质粒与宿主适应性改善的作用，最终阐明pBHB与宿主7D-2的补偿性进化机制。预期成果将丰富代谢型质粒与宿主补偿性进化的理论，也为质粒介导的生物强化修复技术的应用提供理论指导。

The evolution of catabolic plasmid is an important mechanism for bacteria to adapt to organic pollutant contaminated-environment. However, the plasmid replication, conjugative mobilization and gene expression will also bring corresponding physiological burden to its host. Therefore, plasmid tends to reduce its host burden, improve self-stability and mobilization in host populations through compensatory evolution with its host. However, few studies on the co-evolution of catabolic plasmids with their hosts have been carried out, hindering the application of plasmid-mediated bioaugmentation for the bioremediation of organic pollutant contaminated-sites. In this project, we will carry out the co-evolution research of the halogenated aromatic-catabolic plasmid pBHB (belongs to IncP-1β subgroup) with its host Comamonas sp. 7D-2 under the selective pressure of 3,5-dibromo-4-hydroxybenzoate, assess the adaptability of co-evolutionary plasmid to its host, reveal the roles of plasmid gene loss, constrictive regulation of the expression of the catabolic gene cluster and compensatory mutation of core genes of plasmid and host chromosome on the adaptability of plasmid to its host, and finally elucidate the mechanisms involved in the compensatory evolution of pBHB with its host strain 7D-2. The expected results will enrich the theory of compensatory evolution of catabolic plasmids with their hosts, and provide theoretical guidance for the application of plasmid-mediated bioaugmentation for bioremediation.