Dynamic Properties of Picoplankton Over the Annual Cycle in Near-Polar Lakes

近极地湖泊微型浮游生物年度循环的动态特性

• 批准号: 9907776
• 负责人: Don Button
• 金额: $ 34.64万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-11-01 至 2003-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9907776&HistoricalAwards=false
• 关键词: Dynamic; Properties; Picoplankton; Over; Annual

9907776Button This project will examine the dynamic properties of picoplankton over the annual cycle in near-polar lakes. Investigations will focus on describing typical bacterial species from a near-arctic freshwater system during the severe transition in primary productivity and temperature, infer the presence of key organics in theirmaintenance, and quantify the contribution of these mostly undescribed organisms to carbon dioxide production rates. The study site, Harding Lake, is known to have a relatively stable bacterial biomass over the annual cycle. However physical properties of the bacteria, DNA distributions, kinetic constants and associated amino acid concentrations and primary productivities varydramatically between summer and winter. Focus is on the predominatecultivation-resistant bacteria with attention to the small low-DNA forms. Thesewill be isolated and probed for their activity and ability to utilize variouscarbon sources including those expected from the hydrolysis of plant material. A number of novel approaches will be used. These include recently perfectedmeasures of population, biomass per cell, cell volume, DNA content, and genome size by flow cytometry. A chromosome-ratio method for growth rate will be verified at low values, temperature corrections reevaluated, and the method used as a probe of in situ rates of growth with verification by dilution culture.DAPI-DNA assays will be corrected for A+T bias by simultaneously evaluating G+C content of individual bacteria, thereby improving subpopulation resolution.Additional single-cell activity probes include RNA, reducing power and membrane potential for following activity in dilution cultures and more thoroughlycharacterizing in situ populations over the annual cycle. Extinction culturesthat depend on naturally produced sources of carbon are used to isolate bacteriawithout bias toward large fast-growing forms. Cultures are partitioned againstraw lakewater through diffusion membranes to improve culturability. Data areused to determine viabilities as well as the number of species present byincorporating novel formulae as well as DGGE techniques to identify the numberof species in developing populations. Useful carbon sources are evaluatedaccording to flow cytometry patterns from the extinction cultures followingnutrient amendments. Substrates used are taken as an indication of those present and kinetic measurements suggest their concentrations. Ability to use substrates at small concentrations is compared directly according to specific affinity and oligotrophic capacity as recently defined. Isolated species are identified by 16-S ribosomal RNA analysis, and in situ carbon dioxide evolution is calculated from growth rates according to the active (total less very low-DNA) biomass and associated rates of growth. Temperature effects on both uptake and growth are evaluated without carbon-source amendment to determine if rates at low temperatures collapse, or if sufficient membrane potential is sustained tomaintain the required specific affinities.

这个项目将研究近极地湖泊中浮游生物在年循环中的动态特性。研究将集中于描述在初级生产力和温度的严重转变期间来自近北极淡水系统的典型细菌物种，推断维持它们的关键有机物的存在，并量化这些大多数未被描述的生物对二氧化碳生产速率的贡献。研究地点，哈定湖，已知在年循环中有相对稳定的细菌生物量。然而，细菌的物理性质、DNA分布、动力学常数和相关的氨基酸浓度和初级生产力在夏季和冬季之间变化很大。重点是主要的培养抗性细菌，并注意小的低dna形式。这些将被分离和探测它们的活性和利用各种碳源的能力，包括那些从植物材料的水解中预期的碳源。将使用一些新颖的方法。这些包括最近通过流式细胞术完善的人口、每细胞生物量、细胞体积、DNA含量和基因组大小的测量。染色体比率法的生长率将在低值进行验证，温度校正将重新评估，该方法将被用作原位生长率的探针，并通过稀释培养进行验证。DAPI-DNA分析将通过同时评估单个细菌的G+C含量来纠正A+T偏差，从而提高亚群分辨率。其他单细胞活性探针包括RNA，降低功率和膜电位，用于稀释培养中的活性，以及更彻底地描述年周期内的原位种群。依靠自然产生的碳源的灭绝培养被用来分离细菌，而不偏向于快速生长的大型细菌。通过扩散膜将培养物与稻草湖水分开，以提高培养性。通过结合新的公式和DGGE技术来确定发展中种群中的物种数量，数据被用于确定生存能力和存在的物种数量。根据营养修正后消失培养物的流式细胞术模式评估有用的碳源。所使用的底物被视为存在的指示物，动力学测量表明它们的浓度。利用小浓度底物的能力直接根据最近定义的特定亲和力和寡营养能力进行比较。通过16-S核糖体RNA分析鉴定分离的物种，根据活性（总较少的非常低的dna）生物量和相关的生长速率计算生长速率来计算原位二氧化碳进化。在没有碳源修正的情况下，评估温度对吸收和生长的影响，以确定低温下的速率是否会崩溃，或者是否有足够的膜电位维持所需的特定亲和力。