Bacterial decomposition of recalcitrant dissolved organic matter in estuarine systems

本项目将研究Weser河口盐度梯度下细菌群落对顽固性和腐殖质溶解性有机物（DOM）的分解。将使用三级化学调节剂，由天然DOM或特定DOM馏分通过切向流超滤和/或吸附层析用XAD树脂分离，并由来自Weser河口的微咸和海洋细菌群落接种。目的是在原位条件下，富集、鉴定和分离河口微咸段和海相段分解DOM的细菌。天然DOM和分解DOM将通过有机碳高温燃烧、气相色谱和质谱联用热解以及高效液相色谱进行分析。通过变性梯度凝胶电泳（DGGE）和PCR扩增的16S rRNA基因片段测序分析细菌群落和分离菌株的组成。感兴趣的细菌将通过实时PCR在趋化器和原位进行定量。在第二步中，将对选定的分离物或确定的混合培养物进行分解实验，以阐明分离物的生理特性。

In this project the decomposition of recalcitrant and humic dissolved organic matter (DOM) by bacterial communities in the salinity gradient of the Weser estuary will be investigated. Three-stage chemostats, fed by natural DOM or specific DOM fractions isolated by tangential flow ultrafiltration and/or adsorption chromatography with XAD resins and inoculated by brackish and marine bacterial communities from the Weser estuary, will be applied. The aim is to enrich, identify and isolate those bacteria of the brackish and marine section of the estuary which decompose the DOM under in situ conditions. The natural and decomposed DOM will be analyzed by high temperature combustion of organic carbon, pyrolysis coupled with gas chromatography and mass spectrometry, and by HPLC. The composition of the bacterial communities and isolated strains will be analyzed by denaturing gradient gel electrophoresis (DGGE) and sequencing of PCR amplified 16S rRNA gene fragments. Bacteria of interest will be quantified in the chemostats and in situ by real time PCR. Decomposition experiments with selected isolates or defined mixed cultures will be carried out in a second step to elucidate the physiological properties of the isolates.