How Listeria monocytogenes organizes its surface for virulence

Abstract

Listeria monocytogenes is a Gram-positive pathogen responsible for the manifestation of human listeriosis, an opportunistic foodborne disease with an associated high mortality rate. The key to the pathogenesis of listeriosis is the capacity of this bacterium to trigger its internalization by non-phagocytic cells and to survive and even replicate within phagocytes. The arsenal of virulence proteins deployed by L. monocytogenes to successfully promote the invasion and infection of host cells has been progressively unveiled over the past decades. A large majority of them is located at the cell envelope, which provides an interface for the establishment of close interactions between these bacterial factors and their host targets. Along the multistep pathways carrying these virulence proteins from the inner side of the cytoplasmic membrane to their cell envelope destination, a multiplicity of auxiliary proteins must act on the immature polypeptides to ensure that they not only maturate into fully functional effectors but also are placed or guided to their correct position in the bacterial surface. As the major scaffold for surface proteins, the cell wall and its metabolism are critical elements in listerial virulence. Conversely, the crucial physical support and protection provided by this structure make it an ideal target for the host immune system. Therefore, mechanisms involving fine modifications of cell envelope components are activated by L. monocytogenes to render it less recognizable by the innate immunity sensors or more resistant to the activity of antimicrobial effectors. This review provides a state-of-the-art compilation of the mechanisms used by L. monocytogenes to organize its surface for virulence, with special focus on those proteins that work “behind the frontline”, either supporting virulence effectors or ensuring the survival of the bacterium within its host.

Cationic Nanostructures against Foodborne Pathogens

“…Lysozyme and cationic peptides targeting the L. monocytogenes cell wall to promoted bacterial lysis. The introduction of specific modifications in components of the cell envelope as a strategy developed by bacteria rendered them undetectable to both immune recognition and to the bacteriolytic activity of host defense enzymes such as lysozyme and cationic antimicrobial peptides (Davis and Weiser, 2011; Carvalho et al, 2014). It seems that L. monocytogenes did not develop yet any mechanism against DODAB or Gr so that these might be advantageously employed in anti- L. monocytogenes coatings.…”

VirR-Mediated Resistance of Listeria monocytogenes against Food Antimicrobials and Cross-Protection Induced by Exposure to Organic Acid Salts

“…Likewise, the proposed mechanisms of action for LAE (7,8), EPL (9)(10)(11)(12), and CHI (13,14) employ the common theme of cell envelope disruption followed by concomitant disturbances in membrane-related cellular functions, though the exact molecular mechanisms of action remain to be further elucidated. From a bacterial perspective, the cell envelope not only provides structure to the cell but also functions as the primary barrier to exogenous aggressions as well as a virulence modulator at the pathogen-host interface (15). Thus, maintaining the integrity and function of the cell envelope under fluctuating environmental conditions is critical for ensuring bacterial survival and transmission.…”

Genetic subtyping of <i>Listeria monocytogenes</i> via multiple-locus sequence typing using <i>iap, sigB</i> and <i>actA</i>

“…The iap mutation leads to the reduction of virulence, but systemic infections are caused [3]. It is thought that the virulence-promoting function of Iap protein (p60) has been due to its cell wall hydrolysis ability [28].…”