Small Scale Spatial and Temporal Variations in Bacterial Activity in Marine Waters

海洋中的细菌在通过呼吸将溶解的有机物质转化为CO2和转化为微生物食物网内的更高营养级可获得的生物质方面发挥关键作用。它们是海洋中生物量的主要形式。从高产的沿海和上升流区域到极端贫营养的沃茨，细菌丰度分别仅在约10至10毫升之间。然而，这些细菌的活性变化更大。通常检查的米到公里的空间尺度可能不适合小于10-6英寸的细胞，并且可能出现在10-5到10-3 M尺度的斑块中。微尺度的斑块可以提供浓度的有机营养物质的细胞远远高于散装方法测量，导致非常不同的预测细菌的物理和地球化学扰动的反应。在这个项目中，我们建议使用自动化流式细胞仪和成像细胞仪结合灵敏的荧光方法来测量海洋细菌的单细胞组成和活性在小的空间和昼夜时间尺度。各种单细胞荧光探针将用于指示细胞组成，如蛋白质和核酸含量，以及生理过程，如呼吸，膜电位和酶活性。这些单细胞反应将使用自动化流式细胞术和成像细胞术方法进行定量，以提高灵敏度和计数精度，定量荧光/细胞测量和客观检测-所有这些都优于目视显微镜方法。我们的实验室在这些方法方面拥有独特的装备和经验。将比较批量和单细胞方法。将在一系列空间尺度和自然湍流混合条件下研究细菌活动（以及丰度）的微尺度斑块。将在季节周期和营养梯度上测量活性细菌种群和总细菌种群的大小分布，提供浮游生物群落结构的各种状态。还将研究细菌活性的短时间变化，以确定细菌活性如何在昼夜循环中变化。实验将在季节性时间尺度上进行，并在从多产的沿海沃茨到贫营养的蓝水地点的巡航中进行。通过在适当的小空间和短时间尺度上测量单细胞活动，但跨越温带海洋的主导生态梯度，我们将获得控制细菌生物地球化学过程的机制的重要见解。

Bacteria in the ocean play a key role in transforming dissolved organic matter into C02 through respiration and into biomass that is available to higher trophic levels within the microbial food web. They are the dominant form of biomass in the ocean. From highly productive coastal and upwelling regions to extremely oligotrophic waters, bacteria abundances range only between about 10 to 10 ml, respectively. The activity of these bacteria, however, varies much more widely. Typically examined spatial scales of meters to kilometers may not be appropriate for cells that are smaller than 10-6 in and may occur in patches on the scale of 10-5 to 10-3 M. Microscale patchiness can provide concentrations of organic nutrients to cells much higher than those measured by bulk methods, leading to very different predictions of bacterial responses to physical and biogeochemical perturbations. In this project we propose to use automated flow and imaging cytometry combined with sensitive -fluorescence methods to measure the single-cell composition and activity of marine bacteria at small spatial and diel temporal scales. A variety of single-cell fluorescent probes will be used to indicate cell composition such as protein and nucleic acid content, and physiological processes such as respiration, membrane potential, and enzyme activity. These single-cell responses will be quantified using automated flow and imaging cytometric methods for increased sensitivity and count precision, quantitative fluorescence per cell measurement, and objective detection - all improvements over visual microscope methods. Our laboratory is uniquely equipped and experienced in these approaches. Bulk and single- cell methods will be compared. Microscale patchiness of bacterial activity (as ell as abundance) will be examined over a range of spatial scales and natural turbulent mixing conditions. The size distributions of active and total bacterial populations will be measured over seasonal cycles and across trophic gradients providing a variety of regimes of plankton community structure. Short time variations in bacterial activity will also be studied to determine how bacterial activity varies over diel cycles. Experiments will be conducted over seasonal time scales and on cruises from productive, coastal waters to oligotrophic, blue water sites. By measuring single-cell activities at appropriately small spatial and short temporal scales, but across the dominant ecological gradients of the temperate ocean we will gain significant insight into the mechanisms controlling bacterial biogeochemical processes.