Dissertation Research: Production of Microbial ExtracellularPolysaccharides and Their Assimilation by Stream Invertebrates

微生物胞外多糖普遍存在于淹没水表面的水表皮中，但它们对这些生态系统中碳转移的意义尚不清楚。拟议的研究将估计Ogeechee河（第6级黑水河）木材基质上细菌和藻类生物量的产量以及微生物胞外多糖的产量，并测量细胞外多糖被若虫和寡聚毛藻吸收的效率。细胞外多糖的同化作用将通过使用14C标记的细胞外多糖进行饲养研究来确定。这些多糖将从从Ogeechee河中淹没的木材中分离出来的产泥细菌的培养物中纯化出来。溪边水槽中的橡木销子将被用作微生物定植的基质。如果细胞外多糖被淡水无脊椎动物吸收，微生物对无脊椎动物生产力的贡献将远远大于单独估计细胞消耗的结果。这些微生物代谢产物的同化可能有助于满足许多水生生境中细胞微生物生物量不足以满足营养物需求的营养物碳需求。这项研究应该具有重要的基本生态意义，并产生对河流管理有意义的结果。该学生的导师是一位优秀的科学家，学校设施也很好。生态系统研究计划建议支持此博士论文改进项目。

Microbial extracellular polysaccharides are ubiquitous in the epilithon covering submerged lotic surfaces, yet their significance to carbon transfer in these ecosystems is unknown. The proposed research will estimate production of bacterial and algal biomass and the production of microbial extracellular polysaccharide on wood substrates in the Ogeechee River, a sixth order blackwater river, and measure the efficiency with which extracellular polysccharide may be assimilated by nymphal ayflies and by oligochaets. Assimilation of extracellular polysaccharide will be determined by feeding studies using 14C labelled extracellular polysaccharides. These polysaccharides will be purified form cultures of slime-producing bacteria which have been isolated from wood submerged in the Ogeechee River. Oak dowels in stream-side flumes will be used as subtrates for microbial colonization. If extracellular polysaccharides are assimilated by freshwater invertebrates, the contribution of microbes to invertebrate productivity would be much greater than suggested by estimates of cellular consumption alone. The assimilation of these products of microbial metabolism may contribute to meeting detritivore carbon requirements in many aquatic habitats where cellular microbial biomass is insufficient to meet detritivore needs. This research should be of significant basic ecological interest and produce results with meaning for stream management. The student's mentor is an excellent scientist, and institutional accommodations are good. The Ecosystem Studies Program recommends support for this doctoral dissertation improvement project.