Bacterial decomposition of recalcitrant dissolved organic matter in estuarine systems

在本项目中，我们将研究西沙河口盐度梯度内细菌群落对难降解和腐殖质溶解有机物(DOM)的分解。将应用三级恒化器，由天然DOM或通过切向流超滤和/或XAD树脂吸附层析分离的特定DOM组分喂养，并接种来自Weser河口的咸水和海洋细菌群落。目的是丰富、鉴定和分离在现场条件下分解DOM的河口微咸水和海洋部分的细菌。采用有机碳高温燃烧、裂解-气相色谱-质谱联用、高效液相色谱对天然DOM和分解后的DOM进行分析。细菌群落和分离菌株的组成将通过变性梯度凝胶电泳法(DGGE)和PCR扩增的16S rRNA基因片段测序进行分析。感兴趣的细菌将在恒化器中进行量化，并通过实时荧光聚合酶链式反应进行原位检测。第二步将对选定的菌株或已定义的混合培养物进行分解实验，以阐明这些菌株的生理特性。

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.