Bacterivory in Pelagic Marine Ecosystems

细菌是通过微生物环路了解物质和能量的流动以及控制海洋中细菌数量的关键过程。在衡量放牧对细菌影响的各种方法中，最有希望和最广泛使用的三种方法--抑制剂、稀释剂和荧光粒子--建立在关于实验操作对细菌消费者行为的影响的微不足道的假设上。这项研究的主要目标是培育重组缺陷的、对紫外线敏感的海洋细菌菌株(即在短暂暴露于紫外线后仍能继续发挥功能但不能分裂的细胞)。这些细胞将被用来检验现场方法的假设，并阐明食菌原生动物的取食行为(例如，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，较大的海洋生物吞噬细菌的程度和海洋食物链中的燃料生产尚不清楚。这主要是因为很难量化这些微小生物的放牧率。这项工作将把生物技术应用到细菌放牧的研究中。细菌将被基因改造，这样在暴露在少量的某种光(称为紫外线)下后，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，从它们的消失率可以估计出捕食率。除了更好地测量这种速率的重要性外，这种类型的生物技术可能在其他各种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.