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.

细菌在水生生态系统中转化有机碳的作用仅次于浮游植物。据报道，在公海水域，细菌的生物量超过了所有其他活着的浮游生物，即使在大陆架和沿海水域，与其他浮游生物相比，细菌的生物量也是相当大的。然而，这些估计都是基于这样的假设：所有DAPI染色的细胞都是代谢活跃的细胞。这一假设似乎不再站得住脚：很大一部分表面上的细菌要么不活跃，要么垂死，要么死亡。这一结论可能会引发生态系统功能概念模型的另一次范式转变。至少，这将意味着，在给定的时间，相对较少的细菌在原位生长(和呼吸)的速度比之前认为的要快得多，而且相当一部分DAPI染色的细菌要么表现出低活性，要么在操作中是碎屑的组成部分。一种新的荧光染料和分子探针的组合已经被开发出来，它可以定量地识别那些细胞膜受损的细胞，以及那些含有足够的rRNA被认为具有代谢活性的细胞。虽然这两种方法都可能被认为不足以从不活跃、垂死或死亡的细胞中确定活性细胞，但它们共同构成了一个强大的工具，可以在原位研究这些细胞类型的相对重要性，并假设在给定的时间和地点哪些细菌死亡或刺激来源可能是重要的。最近和继续的研究已经彻底评估和证实了生命染色和探针(VSP)方法的适用性，以定量和明确地区分活细胞、非活细胞和低活性细胞。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的浓度，操作上定义为悬浮的非生物POC。这些努力包括新开发的图像分析协议和算法，以识别和计数不同的VSP细胞组，以及游离细菌和附着细菌。在这里，机制研究将调查环境参数对细菌VSP染色模式的影响；进行季节性横断面以确定生产力和碎屑梯度上的自然细菌群落的生理状态；以及测量自然群落和相关碎屑对美国东南大陆架外部上升流诱导的浮游植物水华的随时间变化的响应。特别令人感兴趣的是评估生物意义(如果有的话)和代谢活跃人群比例变化的触发因素。归根结底，意义可能不在于它是活跃的群落的40%还是60%，而是特定的官能团是活跃的还是缓慢增长的，例如硝酸盐还原体。要解决这些问题，必须首先回答这里提出的问题。此外，这些结果将提供一个独特的现场数据集，以评估当前关于细菌在DOC、碎屑和细菌之间转化中所起作用的概念模型。