TRANSCRIPTOME ANALYSIS OF L. MONOCYTOGENES 10403S PROPHAGE: FROM LYSOGENY AND LYTIC INDUCTION TO ACTIVE LYSOGENY

The human bacterial pathogen Listeria monocytogenes harbors a prophage within its genome, which is known to reproduce by both lytic and lysogenic cycles. We have previously shown that this prophage adopts an unusual behavior when L. monocytogenes infects mammalian cells. During macrophage cells infection the prophage, which is inserted within comK gene, excises its genome leaving an intact comK gene that is necessary to facilitate bacterial phagosomal escape. Even though, phage excision occurs, it does not lead to generation of progeny virions and bacterial lysis, suggesting that the prophage cooperates with it host to promote successful mammalian cells infection. We termed this novel phage behavior active lysogeny, as the prophage is highly active transcriptionally and genomically yet preserves the lysogenic mode.

In attempt to better understand the bacterial – phage interaction during active lysogeny, in particular the regulatory mechanisms that control this unusual interaction, we first sought to study the phage transcription profile under the three life cycles: lysogenic, lytic and active lysogeny. Using genome-wide RNA-seq analysis and Nano-string analysis, we identified distinct phage transcription profiles for each cycle, insinuating specific modes of regulation. Several phage regulatory factors were identified and found to regulate the different phage expression modules. The data also pointed phage factors that are differently controlled during active lysogeny, which are now targets for future studies.