CHARACTERIZING DETERMINANTS THAT AFFECT L.MONOCYTOGENES PHAGE PRODUCTION

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that invades a wide array of mammalian cells. This bacterium harbors a prophage within its genome, which is known to reproduce by both lytic and lysogenic cycles. During macrophage cells infection the prophage, which is inserted within the 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.

The objective of this work is to characterize phage and bacterial determinants that affect L. monocytogenes phage production.

We screened phage mutants, and identified essential genes for lytic production, genes that are not essential but important to the lytic cycle and genes that are not involved in lytic production, suggesting their relevance to other life states of the phage.

Additionally, we examined bacterial key regulators to reveal the cross regulation between the phage and its host. Interestingly, L. monocytogenes 10403s strain harbors a specific point mutation in the quorum sensing response regulator agrA encoding gene, leading to a frame shift which generates a truncated protein. Here we present that upon an introduction of a "Fixed" AgrA protein from the EGD-E strain, the lytic production of the phage increases, suggesting a cross-talk between the quorum sensing system of the bacteria and the phage.