Bacterivory in Pelagic Marine Ecosystems

点击翻译按钮获取中文摘要

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.