Patterns and Mechanisms of Variability in the Physiological State of Bacteria in Marine Pelagic Environments

海洋远洋环境中细菌生理状态变异的模式和机制

• 批准号: 9906734
• 负责人: Marc Frischer
• 金额: --
• 依托单位: Skidaway Institute of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9906734&HistoricalAwards=false
• 关键词: Patterns; Mechanisms; Variability; Physiological; State

Frischer 9906734Bacteria are thought to be second only to phytoplankton in their role of transforming organic carbon in aquatic ecosystems. In open ocean waters, the biomass of bacteria has been reported to exceed that of all other living plankton, and even in continental shelf and coastal waters it is significant compared to other plankton. However, these estimates are all derived from the assumption that all DAPI-stained cells are metabolically active cells. This hypothesis no longer appears tenable: a large fraction of apparent bacteria are either inactive, moribund, or dead. Such a conclusion threatens to precipitate another paradigm shift in conceptual models of ecosystem function. At the very least, it would imply that, at a given time, comparatively few bacteria in situ are growing (and respiring) much faster than previously thought, and that a substantial fraction of DAPI-stained bacteria either exhibit low activity or are operationally a component of detritus.A novel combination of a fluorescent stain and molecular probes has been developed which quantitatively identify those cells with compromised membranes, and those cells containing sufficient rRNA to be considered metabolically active. While neither approach might be considered sufficient to specify active from inactive, moribund, or dead cells, together they comprise a powerful tool to investigate the relative importance of these cell types in situ, and to postulate which sources of bacterial mortality or stimulation may be important at a given time and place. Recent and continuing studies have thoroughly evaluated and confirmed the applicability of the vital stain and probe (VSP) method to quantitatively and unambiguously discriminate among living, nonliving, and low activity cells. In a related but separate study, a quantitative technique also has been developed to determine concentrations of detritus, operationally defined as suspended nonliving POC. These efforts include newly developed image analysis protocols and algorithms to recognize and enumerate the different groups of VSP cells, and also free vs. attached bacteria.Here, mechanistic studies will investigate the effects of environmental parameters on patterns of VSP staining of bacteria; conduct seasonal transects to determine the physiological status of natural bacterial communities across a productivity and detritus gradient; and measure the time-dependent response of natural communities and associated detritus to upwelling-induced phytoplankton blooms on the outer U.S. southeastern continental shelf. Of special interest are evaluating the biological significance (if any) and the triggers of shifts in the fraction of metabolically active populations. Ultimately, the significance may not lie in whether it is 40% vs. 60% of a community which is active, but whether specific functional groups are active or slow growing, e.g. nitrate reducers. To address such issues, the questions posed here must first be answered. Moreover, the results will provide a unique field dataset to evaluate current conceptual models of the role of bacteria in transformations between DOC, detritus, and bacteria.

弗里舍（Frischer）9906734细菌被认为仅次于浮游植物，在其在水生生态系统中转化有机碳的作用。据报道，在开放海水中，细菌的生物量超过了所有其他活浮游生物的生物量，即使在大陆架子和沿海水域，与其他浮游生物相比，它也很重要。但是，这些估计都来自以下假设：所有DAPI染色的细胞都是代谢活性细胞。该假设不再看起来很容易：很大一部分明显的细菌是无活跃，垂死或死亡的。这样的结论可能会在生态系统功能的概念模型中促成另一种范式转移。至少，这意味着，在给定的时间，相对较少的细菌在原位增长（和呼吸）比以前想象的要快得多，并且大量的DAPI染色细菌的一小部分要么表现出较低的活性，要么表现出较低的活性，或者在操作上已经是损坏的组成部分。 rRNA被认为是代谢活性的。尽管两种方法都可以被认为足以从非活性，垂死或死细胞中指定活动，但它们共同构成了研究这些细胞类型的相对重要性的强大工具，并假定在给定时间和地点，哪些细菌死亡率或刺激来源可能很重要。最近和继续进行的研究已经对生命，非生命和低活性细胞之间的定量和明确区分，对重要污渍和探针（VSP）方法的适用性进行了彻底评估和确认。在一项相关但独立的研究中，还开发了一种定量技术来确定碎屑浓度，在操作上定义为悬浮的非生存POC。这些努力包括新开发的图像分析方案和算法，以识别和列举不同的VSP细胞，以及自由与附着的细菌。在此，机械研究将研究环境参数对细菌VSP染色模式的影响。进行季节性样品，以确定生产力和碎屑梯度跨生产力的天然细菌群落的生理状况；并衡量自然社区和相关的碎屑对上流诱导的浮游植物在美国东南大陆架上的浮游生物的响应。特别感兴趣的是评估生物学意义（如果有的话）和代谢活跃种群的偏移的触发器。最终，意义可能不在于它是40％和活跃的社区的60％，而是特定的官能团体是活跃还是增长缓慢，例如硝酸盐还原器。为了解决此类问题，必须首先回答此处提出的问题。此外，结果将提供一个独特的现场数据集，以评估细菌在DOC，碎屑和细菌之间转化中的作用的当前概念模型。