Abstract

The study of bacterial pathogenesis is in many ways the study of the regulatory mechanisms at work in the microbe during infection. The astonishing flexibility and adaptability of the bacterial cell has enabled many pathogenic species to freely transition between dramatically different environmental conditions. The transcriptional changes that underlie this ability can determine the success of the pathogen in the host. Many techniques have been devised to examine the transcriptional repertoire of bacteria in vivo during infection. Here, we review a class of technologies known as in vivo expression technology (IVET), which use promoter-trapping with a variety of different reporter constructs to allow researchers to probe the transcriptional changes taking place in bacteria under various environmental conditions. Using IVET techniques, researchers have been able to catalogue a wide variety of virulence factors in the host for several important human pathogens, as well as examining the timing of virulence gene regulation. Most recently, IVET techniques have also been used to identify transcriptional repression events in vivo, such as the suppression of anti-colonization factors deleterious to infection. As the array of IVET reporters and promoter-trapping strategies grow, researchers are increasingly able to illuminate the myriad transcriptional activities that allow bacteria to survive and cause disease in the host.