STARTER GRANT: Characterization of Catabolic Pathways for the Degradation of Plant-related Aromatics in the Marine Bacterium Silicibacter Pomeroyi

芳香聚合物木质素及其相关化合物的再矿化对全球碳循环至关重要，但人们对其自然群落和涉及的过程知之甚少。美国东南部的沿海盐沼受到当地和外地来源的木质素相关化合物的严重影响，是研究分解者群落中隐藏的分解代谢途径的理想地点。海洋细菌的一个分支--玫瑰杆菌支系的成员特别适合于这样的研究，因为它们在这些沿海盐沼中大量存在，并被假设对这些系统中芳香化合物降解的很大一部分负责。本项目以玫瑰色杆菌分离株为研究对象，利用基因组数据、生理生长研究和基因表达水平来更好地了解分解代谢过程和调控网络，这些过程和调控网络介导了木质素单体组分的转化。其目的是：(I)确定可被Pomeroyi用作主要生长底物的木质素相关化合物；(Ii)确定三种途径中的哪一条将会分解底物，即PCA、龙胆酸或Boxa；利用分子方法监测三个途径关键酶的基因表达水平。对S.pomeroyi分解代谢特性的详细描述将为了解自然产生的芳香化合物是如何被环境中的Rosebacter谱系成员处理所需的关键基础。该项目将通过其对阐明代谢网络的贡献而产生广泛的影响，代谢网络控制着碳的生物地球化学循环的中心过程。此外，它还将支持一名研究生和两名本科生的培训机会。

The remineralization of the aromatic polymer lignin and its related compounds is critical to the global carbon cycle, yet little is known of the natural communities and the processes involved. The coastal salt marshes of the southeastern U.S. are heavily influenced by lignin-related compounds of local and allochthonous origins, and are ideal sites for investigations of catabolic pathways that are harbored within decomposer communities. Members of one lineage of marine bacteria, the Roseobacter clade, are particularly well-suited for such studies as they are abundant in these coastal salt marshes and are hypothesized to be responsible for a significant fraction of aromatic compound degradation in these systems. This project focuses on Roseobacter isolate Silicibacter pomeroyi and uses genome data, physiological growth studies, and gene expression levels to better understand the catabolic processes and regulatory networks mediating the transformation of the monomeric constituents of lignin by members of this group.The genome sequence of S. pomeroyi reveals the presence of three, potentially competing, pathways for the degradation of plant-related aromatic compounds. The aims are to: (i) Identify lignin-related compounds that can be utilized by S. pomeroyi as primary growth substrates, (ii) identify which of the three pathways, pca, gentisate, or boxA, will catabolizable substrates, and iii. utitlize molecular approaches to monitor gene expression levels of key enzymes of the three pathways. Detailed characterizations of the catabolic properties of S. pomeroyi will provide the critical foundation needed to understand how naturally-occurring aromatic compounds are processed by members of the Roseobacter lineage in the environment.This project will have broad impact through its contribution toward the elucidation of metabolic networks that govern processes central to the biogeochemical cycling of carbon. Moreover, it will support training opportunities for one graduate student and two undergraduate students.