Bacterivory in Pelagic Marine Ecosystems

细菌学是了解海洋微生物循环中物质和能量流动以及控制细菌丰度的关键过程。在测量放牧对细菌影响的各种方法中，最有前途和最广泛使用的三种方法-抑制剂，稀释和荧光颗粒-基于关于实验操作对细菌消费者行为影响的脆弱假设。本研究的主要目的是培养重组缺陷、对紫外线敏感的海洋细菌菌株（即在短暂暴露于紫外线后将继续发挥功能但不能分裂的细胞）。这些细胞将用于测试野外方法的假设，并阐明细菌原生动物的摄食行为（如大小选择）。细菌在海洋环境中无处不在，浓度从每立方厘米数十万到数百万不等。然而，我们对海洋细菌的性质和对海洋生物系统的影响的了解是有限的。例如，目前尚不清楚细菌在多大程度上被大型海洋生物吃掉，以及海洋食物网中的燃料生产。这主要是由于难以量化这些微小生物的放牧率。这项工作将为细菌放牧研究提供一种新的生物技术应用。细菌的基因将被改变，因此在暴露于少量某种光线（称为紫外线）后，细菌将无法分裂，尽管它们将继续发挥作用。因此，这种改变的细菌可以作为正常细菌的类似物，并且可以从它们的消失率估计放牧率。除了更好地测量这种速率的重要性之外，这种生物技术可能在各种其他海洋学应用中被证明是有用的。

Bacterivory is a key process in understanding the flux of matter and energy through the microbial loop and the control of bacterial abundance in the oceans. Of the various approaches to measuring grazing impact on bacteria, three of the most promising and widely used methods - inhibitors, dilution, and fluorescent particles - rest on tenuous assumptions regarding the effects of experimental manipulations on the behaviors on bacterial consumers. The primary objective of this study is to develop recombination-deficient, UV sensitive strains of marine bacteria (i.e. cells that will continue to function but cannot divide following brief exposure to UV light). These cells will be used to test the assumptions of the field methods and elucidate feeding behaviors (e.g. size selection) of bacterivorous protozoa. Bacteria are ubiquitous in the marine environment and range in concentration from hundreds of thousands to millions per cubic centimeter. However, our understanding of the nature and impact of marine bacteria on marine biological systems is limited. For example, the degree to which bacteria are eaten by larger marine organisms and fuel production in the marine food web is unclear. This is mainly due to the difficulty in quantifying grazing rates on these minute organisms. This work will apply a novel application of biotechnology to the study of bacterial grazing. Bacteria will be genetically altered so that after exposure to a small amount of a certain kind of light (called ultraviolet), the bacteria will not be able to divide, although they will continue to function. Thus, such altered bacteria can serve as analogs for normal bacteria and grazing rates can be estimated from their rate of disappearance. In addition to the importance of making better measurements of such rates, this type of biotechnology may prove useful in a variety of other oceanographic applications.