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Publisher Summary This chapter focuses on experimental approaches to study global regulation in Escherichia coli (E. coli ). The advantages and disadvantages of using global regulators can be illustrated by using an economic analogy. Bacteria, which often live in highly competitive environments and are not protected by the homeostases provided to the cells of multicellular organisms, cannot afford to have a welter of uncoordinated responses to a change in temperature or nutrient availability. One of the first questions encountered in studying global regulation involves the breadth of the particular regulon—that is, the number of genes that are regulated. Various methods are available, both in vitro and in vivo , to help answer this question. Each method has its own strengths and weaknesses, but a combination of several methods often serves to gain a good understanding of a regulon's size and sometimes even a hint of the class to which the relevant regulator belongs. There are now numerous methods for determining which genes and proteins belong to a given regulon. The signal transduction pathway in the nitrogen regulon has been elicited in detail by in vitro studies with purified components, and the interaction of the transcriptional activator—NR I —with at least one target gene— glnA —is understood at the molecular level. |
