The EXIT Strategy: an Approach for Identifying Bacterial Proteins Exported during Host Infection.

Exported proteins of bacterial pathogens function both in essential physiological processes and in virulence. Past efforts to identify exported proteins were limited by the use of bacteria growing under laboratory () conditions. Thus, exported proteins that are exported only or preferentially in the context of infection may be overlooked. To solve this problem, we developed a genome-wide method, named EXIT (ported echnology), to identify proteins that are exported by bacteria during infection and applied it to during murine infection. Our studies validate the power of EXIT to identify proteins exported during infection on an unprecedented scale (593 proteins) and to reveal induced exported proteins (i.e., proteins exported significantly more during infection than ). Our EXIT data also provide an unmatched resource for mapping the topology of membrane proteins. As a new approach for identifying exported proteins, EXIT has potential applicability to other pathogens and experimental conditions. There is long-standing interest in identifying exported proteins of bacteria as they play critical roles in physiology and virulence and are commonly immunogenic antigens and targets of antibiotics. While significant effort has been made to identify the bacterial proteins that are exported beyond the cytoplasm to the membrane, cell wall, or host environment, current methods to identify exported proteins are limited by their use of bacteria growing under laboratory () conditions. Because conditions do not mimic the complexity of the host environment, critical exported proteins that are preferentially exported in the context of infection may be overlooked. We developed a novel method to identify proteins that are exported by bacteria during host infection and applied it to identify proteins exported in a mouse model of tuberculosis.