Reporter Gene Expression for Monitoring Microorganisms in the Environment

Reporter gene is a generic term that is used to describe genes whose expression is indicative of the presence of a particular cell, a specific event occurring within that cell, or a reflection of the expression of other, usually targeted genes of interest. For example, the presence of such a gene may make an organism standout to help in identification, as will be described in this chapter, or it could be that a gene is only expressed under certain conditions, e.g., during different developmental stages (1 ), environmental stresses (2 ,3 ) , or DNA repair as a result of induction of the SOS response to DNA damage (4 ). Naturally-occurring reporter genes can be used to avoid the need for genetic engineering by selecting a unique property of an organism and using it as the reporter. However, by far the commonest approach is to introduce a reporter gene into a cell to allow detection of a particular organism or to monitor its activity. The reporter gene can be located on a plasmid or to increase the stability of the gene within the cell it can be incorporated into the bacterial chromosome. There are a wide variety of reporter genes available, and all have particular properties that make them more or less useful depending on the application (Table 1 ). The choice of a particular reporter gene is made on the basis of the environment into which the organism is to be released, how the gene is to be detected, and what factors might interfere with the detection of the gene and/or its protein product.