Dynamics and compositional changes in extracellular carbohydrates in estuarine sediments during degradation
Dynamics and compositional changes in extracellular carbohydrates in estuarine sediments during degradation
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DOI：
10.3354/meps07875
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发表时间：
2009-01-01
影响因子：
2.5
通讯作者：
Underwood, Graham J. C.
中科院分区：
文献类型：
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作者：
Hofmann, Tanja;Hanlon, Astrid R. M.;Underwood, Graham J. C.
河口沉积物中的微型底栖生物膜由光合微藻、异养细菌及其相关的胞外聚合物组成，含有高浓度的水溶性胶体碳水化合物，可通过乙醇沉淀分离成低分子量的碳水化合物。(LMW)碳水化合物和胶体胞外聚合物(CEP)。这些富含碳水化合物的成分可能是一种重要的碳源，但利用过程并未得到很好的描述。使用提高胶体碳水化合物和CEPS浓度的沉淀物浆液进行的短期(24小时)降解研究发现，低分子碳水化合物浓度在前4小时迅速增加，随后在8到24小时后利用低分子碳水化合物和CEPS。在对照和胶体碳水化合物丰富的泥浆中，CEPS对胶体碳水化合物池的贡献增加(16%到67%到97%)，24小时后葡萄糖降低，EPS组分中甘露糖和木糖含量增加，这表明最初使用富含葡萄糖的成分，而不是更复杂的EPS。当CEPS浓度增加(CEPS浓缩)时，EPS的利用率更高，EPS的相对贡献率下降(占胶体碳水化合物部分的72%至31%)，而CEPS部分中的单糖组成没有明显变化。以CEPS为唯一碳源的选择性培养基产β-变形杆菌Variovorax sp.Alr1被分离出来。Variovorax sp.AM在作为唯一碳源的CEPS上生长迅速，β-葡萄糖苷酶活性增加，并产生富含鼠李糖、半乳糖和岩藻糖的新的EPS，但在用热重碳酸盐提取程序从沉积物中提取的EPS上，尽管β-葡萄糖苷酶和氨基肽酶活性增加，但生长有限。不同组分沉积物短期稳定性的差异。碳水化合物和异养菌利用这些组分的能力表明，一系列不同的异养菌可能参与了EPS的原位完全降解。
Microphytobenthic biofilms in estuarine sediments, consisting of photosynthetic microalgae, heterotrophic bacteria and their associated exopolymers, contain high concentrations of water-soluble colloidal carbohydrates that can be separated using ethanol precipitation into low molecular weight. (LMW) carbohydrate and colloidal extracellular polymeric substances (cEPS). These carbohydrate-rich components are potentially a significant carbon Source, but utilisation processes are not well described. Short-term (24 h) degradation studies using sediment slurries with enhanced colloidal carbohydrate and cEPS concentrations found rapid increases in LMW carbohydrate concentrations during the first 4 h, with subsequent utilisation of LMW carbohydrate and cEPS after 8 to 24 h. The cEPS contribution to the colloidal carbohydrate pool increased (16 to between 67 and 97%) in control and colloidal carbohydrate-enriched slurries, with decreasing glucose and increasing mannose and xylose contents within the EPS fraction after 24 h, suggesting initial utilisation Of glucose-rich components in preference to more complex EPS. When cEPS concentrations were increased (cEPS-enrichment), there was greater EPS utilisation, and a decline in the relative contribution of EPS (72 to 31% of the colloidal carbohydrate fraction), without significant change in the monosaccharide, composition in the cEPS fraction. Using selective media with cEPS as a sole carbon source, a beta-proteobacterium Variovorax sp. Alr1 was isolated. Variovorax sp. AM grew rapidly on cEPS as a sole carbon Source, with increasing beta-glucosidase activity and the production of new EPS rich in rhamnose, galactose and fucose, but showed only limited growth on EPS extracted from sediment using a hot-bicarbonate, extraction procedure, despite increases in beta-glucosidase and aminopeptidase activity. Differences in the short-term lability of different fractions of sediment. carbohydrate and the ability of a heterotroph to utilise these fractions suggests a range of different heterotrophic bacteria may be involved in the complete degradation of EPS in situ.