MEASUREMENT OF TRANSCRIPTIONAL ACTIVITY IN PATHOGENIC BACTERIA RECOVERED DIRECTLY FROM INFECTED HOST TISSUE

In order to understand the genetic regulation of bacterial genes whose products are important for pathogenesis, one needs to measure the exp ression of the genes during the infection process. We have devised a m ethod to measure the transcriptional activity of such genes from bacte ria recovered directly from infected host tissue. Starting with bacter ial strains containing lacZ transcriptional fusions to the genes of in terest, animals can be infected, with subsequent isolation of infected host tissue. Here we describe the separation of bacterial cells away from a particular host tissue and the subsequent measurement of the ac tivity of beta-galactosidase, the product of the lacZ gene, in the bac terial cells. This assay is sensitive enough to compensate for the pot entially low number of bacteria recovered fi om the infection site.