Departamento de Biología Marina y Oceanografía, Instituto de Ciencias del Mar (CSIC), 08003 Barcelona, Spain.
Appl Environ Microbiol. 2011 Nov;77(21):7490-8. doi: 10.1128/AEM.00200-11. Epub 2011 Jul 8.
An understanding of the distribution of colored dissolved organic matter (CDOM) in the oceans and its role in the global carbon cycle requires a better knowledge of the colored materials produced and consumed by marine phytoplankton and bacteria. In this work, we examined the net uptake and release of CDOM by a natural bacterial community growing on DOM derived from four phytoplankton species cultured under axenic conditions. Fluorescent humic-like substances exuded by phytoplankton (excitation/emission [Ex/Em] wavelength, 310 nm/392 nm; Coble's peak M) were utilized by bacteria in different proportions depending on the phytoplankton species of origin. Furthermore, bacteria produced humic-like substances that fluoresce at an Ex/Em wavelength of 340 nm/440 nm (Coble's peak C). Differences were also observed in the Ex/Em wavelengths of the protein-like materials (Coble's peak T) produced by phytoplankton and bacteria. The induced fluorescent emission of CDOM produced by prokaryotes was an order of magnitude higher than that of CDOM produced by eukaryotes. We have also examined the final compositions of the bacterial communities growing on the exudates, which differed markedly depending on the phytoplankton species of origin. Alteromonas and Roseobacter were dominant during all the incubations on Chaetoceros sp. and Prorocentrum minimum exudates, respectively. Alteromonas was the dominant group growing on Skeletonema costatum exudates during the exponential growth phase, but it was replaced by Roseobacter afterwards. On Micromonas pusilla exudates, Roseobacter was replaced by Bacteroidetes after the exponential growth phase. Our work shows that fluorescence excitation-emission matrices of CDOM can be a helpful tool for the identification of microbial sources of DOM in the marine environment, but further studies are necessary to explore the association of particular bacterial groups with specific fluorophores.
了解海洋中有色溶解有机物 (CDOM) 的分布及其在全球碳循环中的作用，需要更好地了解海洋浮游植物和细菌产生和消耗的有色物质。在这项工作中，我们研究了在无菌条件下培养的四种浮游植物产生的 DOM 上生长的自然细菌群落对 CDOM 的净吸收和释放。浮游植物分泌的荧光腐殖质类似物（激发/发射波长，310nm/392nm；Coble 峰 M）被细菌以不同的比例利用，这取决于其起源的浮游植物种类。此外，细菌还产生了在 340nm/440nm（Coble 峰 C）处荧光的腐殖质类似物。浮游植物和细菌产生的类蛋白物质（Coble 峰 T）的 Ex/Em 波长也存在差异。原核生物产生的诱导荧光 CDOM 的发射强度比真核生物高一个数量级。我们还研究了在分泌产物上生长的细菌群落的最终组成，这些组成因起源的浮游植物种类而异。在 Chaetoceros sp. 和 Prorocentrum minimum 分泌产物上的所有培养中，交替单胞菌属和玫瑰杆菌属分别占主导地位。在 Skeletonema costatum 分泌产物上生长的优势群体是交替单胞菌属，但随后被玫瑰杆菌属取代。在 Micromonas pusilla 分泌产物上，玫瑰杆菌属在指数生长阶段后被拟杆菌门取代。我们的工作表明，CDOM 的荧光激发-发射矩阵可以成为识别海洋环境中 DOM 的微生物来源的有用工具，但需要进一步研究来探索特定细菌群体与特定荧光团的关联。
