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

9907776按钮 该项目将研究近极地湖泊中微型浮游生物在年周期中的动态特性。调查将集中在描述典型的细菌物种从近北极淡水系统在初级生产力和温度的严重转变，推断存在的关键有机物在theirmaintenance，并量化的贡献，这些大部分未描述的生物二氧化碳生产率。研究地点哈丁湖在年周期中具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。重点是主要的耐培养细菌，注意小的低DNA形式。这些将被分离和探测其活性和利用各种碳源的能力，包括那些预期从植物材料的水解。将采用一些新的办法。这些包括最近完善的测量人口，生物量每细胞，细胞体积，DNA含量和基因组大小的流式细胞术。将在低值下验证用于生长速率的染色体比率方法，重新评估温度校正，并将该方法用作原位生长速率的探针，并通过稀释培养进行验证。将通过同时评估单个细菌的G+C含量来校正DAPI-DNA测定的A+T偏倚，从而提高亚群分辨率。其他单细胞活性探针包括RNA，降低稀释培养物中后续活动的能力和膜电位，并在年度周期内更彻底地表征原位种群。灭绝培养依赖于自然产生的碳源，用于分离细菌，而不会偏向于快速生长的大型形式。通过扩散膜将培养物与稻草湖水分开以提高可培养性。数据被用来确定生活力，以及目前的物种数量，通过纳入新的公式，以及DGGE技术，以确定在发展中国家的种群的物种数量。有用的碳源是根据流式细胞术模式从灭绝文化followingnutritional修正案进行评估。所用的底物被认为是那些存在的指示，动力学测量表明它们的浓度。使用低浓度底物的能力直接根据最近定义的特异性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，并根据活性（总DNA含量较低）生物质和相关生长率从生长率计算原位二氧化碳释放。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崩溃，或者是否维持足够的膜电位以保持所需的特定亲和力。

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.