Bone Marrow-Derived Macrophage (BMDM ) Infection by Listeria monocytogenes.

Listeria monocytogenes is a gram-positive bacterium adapted to life as both an environmental saprophyte and a pathogenic parasite of mammalian hosts, with a transcriptomic program tailored for each niche. Study of the L. monocytogenes pathogenic lifestyle requires conditions that mimic the mammalian niche.

Generation of Markerless Gene Deletion Mutants in Listeria monocytogenes Using a Mutated pheS for Counterselection.

Gene alteration/deletion by allelic exchange is the preferred strategy for gene manipulation in bacteria. Here we present the fundamentals for an efficient allelic exchange gene deletion method in the bacterial pathogen Listeria monocytogenes. Combining vector generation by Gibson assembly with a counterselection system based on the mutated phenylalanine synthetase (pheS*) makes the generation of gene deletion mutants straightforward and time efficient.

A dual-function phage regulator controls the response of cohabiting phage elements via regulation of the bacterial SOS response.

Listeria monocytogenes strain 10403S harbors two phage elements in its chromosome; one produces infective virions and the other tailocins. It was previously demonstrated that induction of the two elements is coordinated, as they are regulated by the same anti-repressor. In this study, we identified AriS as another phage regulator that controls the two elements, bearing the capacity to inhibit their lytic induction under SOS conditions.

Coordination of cohabiting phage elements supports bacteria-phage cooperation.

Bacterial pathogens often carry multiple prophages and other phage-derived elements within their genome, some of which can produce viral particles in response to stress. Listeria monocytogenes 10403S harbors two phage elements in its chromosome, both of which can trigger bacterial lysis under stress: an active prophage (ϕ10403S) that promotes the virulence of its host and can produce infective virions, and a locus encoding phage tail-like bacteriocins. Here, we show that the two phage elements are co-regulated, with the bacteriocin locus controlling the induction of the prophage and thus its activity as a virulence-associated molecular switch.

Temperate bacteriophages as regulators of host behavior.

Bacteriophages are ubiquitous and affect most facets of life, from evolution of bacteria, through ecology and global biochemical cycling to human health. The interactions between phages and bacteria often lead to biological novelty and an important milestone in this process is the ability of phages to regulate their host's behavior. In this review article, we will focus on newly reported cases that demonstrate how temperate phages regulate bacterial gene expression and behavior in a variety of bacterial species, pathogenic and environmental.