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Listeria monocytogenes is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the host's cells and is one of the most virulent foodborne pathogens: 20 to 30% of foodborne listeriosis infections in high-risk individuals may be fatal. Responsible for an estimated 1,600 illnesses and 260 deaths in the United States annually, listeriosis ranks third in total number of deaths among foodborne bacterial pathogens, with fatality rates exceeding even Salmonella spp. and Clostridium botulinum. In the European Union, listeriosis follows an upward trend that began in 2008, causing 2,161 confirmed cases and 210 reported deaths in 2014, 16% more than in 2013. Listeriosis mortality rates are also higher in the EU than for other foodborne pathogens.
An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell. Gram negative pathogens may secrete outer membrane vesicles containing lipopolysaccharide endotoxin and some virulence proteins in the bounding membrane along with some other toxins as intra-vesicular contents, thus adding a previously unforeseen dimension to the well-known eukaryote process of membrane vesicle trafficking, which is quite active at the host-pathogen interface.
Listeria is a genus of bacteria that acts as an intracellular parasite in mammals. Until 1992, 10 species were known, each containing two subspecies. By 2020, 21 species had been identified. The genus received its current name, after the British pioneer of sterile surgery Joseph Lister, in 1940. Listeria species are Gram-positive, rod-shaped, and facultatively anaerobic, and do not produce endospores. The major human pathogen in the genus Listeria is L. monocytogenes. It is usually the causative agent of the relatively rare bacterial disease listeriosis, an infection caused by eating food contaminated with the bacteria. Listeriosis can cause serious illness in pregnant women, newborns, adults with weakened immune systems and the elderly, and may cause gastroenteritis in others who have been severely infected.
In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs).
Virulence factors are cellular structures, molecules and regulatory systems that enable microbial pathogens to achieve the following:
Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named hemolysins, and so on. Cytolysins may be involved in immunity as well as in venoms.
Pascale Cossart is a French bacteriologist who is affiliated with the Pasteur Institute of Paris. She is the foremost authority on Listeria monocytogenes, a deadly and common food-borne pathogen responsible for encephalitis, meningitis, bacteremia, gastroenteritis, and other diseases.
Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acquisition, many hemolysins produced by pathogens do not cause significant destruction of red blood cells during infection. However, hemolysins are often capable of lysing red blood cells in vitro.
The PrfA thermoregulator UTR is an RNA thermometer found in the 5' UTR of the prfA gene. In Listeria monocytogenes, virulence genes are maximally expressed at 37 °C but are almost silent at 30 °C. The genes are controlled by PrfA, a transcriptional activator whose expression is thermoregulated. It has been shown that the untranslated mRNA (UTR) preceding prfA, forms a secondary structure, which masks the ribosome binding region. It is thought that at 37 °C, the hairpin structure 'melts' and the SD sequence is unmasked.
In molecular biology, zinc-dependent phospholipases C is a family of bacterial phospholipases C enzymes, some of which are also known as alpha toxins.
Internalins are surface proteins found on Listeria monocytogenes. They exist in two known forms, InlA and InlB. They are used by the bacteria to invade mammalian cells via cadherins transmembrane proteins and Met receptors respectively. The exact role of these proteins and their invasiveness in vivo is not completely understood. In cultured cells, InlA is necessary to facilitate Listeria entry into human epithelial cells, while InlB is necessary for Listeria internalisation in several other cell types, including hepatocytes, fibroblasts, and epithelioid cells. Internalins are mainly surface-exposed virulence factors present in a number of Gram-positive bacteria whose role ranges from recognition of cellular receptors to aid in pathogen entry to escape from autophagy.
Listeria monocytogenes is a gram positive bacterium and causes many food-borne infections such as Listeriosis. This bacteria is ubiquitous in the environment where it can act as either a saprophyte when free living within the environment or as a pathogen when entering a host organism. Many non-coding RNAs have been identified within the bacteria genome where several of these have been classified as novel non-coding RNAs and may contribute to pathogenesis.
The RTX toxin superfamily is a group of cytolysins and cytotoxins produced by bacteria. There are over 1000 known members with a variety of functions. The RTX family is defined by two common features: characteristic repeats in the toxin protein sequences, and extracellular secretion by the type I secretion systems (T1SS). The name RTX refers to the glycine and aspartate-rich repeats located at the C-terminus of the toxin proteins, which facilitate export by a dedicated T1SS encoded within the rtx operon.
The Actin assembly-inducing protein (ActA) is a protein encoded and used by Listeria monocytogenes to propel itself through a mammalian host cell. ActA is a bacterial surface protein comprising a membrane-spanning region. In a mammalian cell the bacterial ActA interacts with the Arp2/3 complex and actin monomers to induce actin polymerization on the bacterial surface generating an actin comet tail. The gene encoding ActA is named actA or prtB.
The Thiol-activated Cholesterol-dependent Cytolysin(CDC) family is a member of the MACPF superfamily. Cholesterol dependent cytolysins are a family of β-barrel pore-forming exotoxins that are secreted by gram-positive bacteria. CDCs are secreted as water-soluble monomers of 50-70 kDa, that when bound to the target cell, form a circular homo-oligomeric complex containing as many as 40 monomers. Through multiple conformational changes, the β-barrel transmembrane structure is formed and inserted into the target cell membrane. The presence of cholesterol in the target membrane is required for pore formation, though the presence of cholesterol is not required by all CDCs for binding. For example, Intermedilysin secreted by Streptococcus intermedius will bind only to target membranes containing a specific protein receptor, independent of the presence of cholesterol, but cholesterol is required by intermedilysin for pore formation. While the lipid environment of cholesterol in the membrane can affect toxin binding, the exact molecular mechanism that cholesterol regulates the cytolytic activity of the CDC is not fully understood.
Paracytophagy is the cellular process whereby a cell engulfs a protrusion which extends from a neighboring cell. This protrusion may contain material which is actively transferred between the cells. The process of paracytophagy was first described as a crucial step during cell-to-cell spread of the intracellular bacterial pathogen Listeria monocytogenes, and is also commonly observed in Shigella flexneri. Paracytophagy allows these intracellular pathogens to spread directly from cell to cell, thus escaping immune detection and destruction. Studies of this process have contributed significantly to our understanding of the role of the actin cytoskeleton in eukaryotic cells.
Shigatoxigenic Escherichia coli (STEC) and verotoxigenic E. coli (VTEC) are strains of the bacterium Escherichia coli that produce either Shiga toxin or Shiga-like toxin (verotoxin). Only a minority of the strains cause illness in humans. The ones that do are collectively known as enterohemorrhagic E. coli (EHEC) and are major causes of foodborne illness. When infecting humans, they often cause gastroenteritis, enterocolitis, and bloody diarrhea and sometimes cause a severe complication called hemolytic-uremic syndrome (HUS). The group and its subgroups are known by various names. They are distinguished from other strains of intestinal pathogenic E. coli including enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), and diffusely adherent E. coli (DAEC).
Bromo adjacent homology domain containing 1(BAHD1) is a protein that in humans is encoded by the BAHD1 gene. BAHD1 is involved in heterochromatin formation and transcriptional repression.
Proteobiotics are natural metabolites which are produced by fermentation process of specific probiotic strains. These small oligopeptides were originally discovered in and isolated from culture media used to grow probiotic bacteria and may account for some of the health benefits of probiotics.
Nucleomodulins are a family of bacterial proteins that enter the nucleus of eukaryotic cells.
References
- ↑ Cossart P (1988). "The listeriolysin O gene: a chromosomal locus crucial for the virulence of Listeria monocytogenes". Infection. 16 Suppl 2: S157–9. doi:10.1007/BF01639740. PMID 2843472. S2CID 27405024.
- 1 2 Geoffroy C, Gaillard JL, Alouf JE, Berche P (1987). "Purification, characterization, and toxicity of the sulfhydryl-activated hemolysin listeriolysin O from Listeria monocytogenes". Infect. Immun. 55 (7): 1641–6. doi:10.1128/iai.55.7.1641-1646.1987. PMC 260571 . PMID 3110067.
- ↑ Dramsi S, Cossart P (2002). "Listeriolysin O: a genuine cytolysin optimized for an intracellular parasite". J. Cell Biol. 156 (6): 943–6. doi:10.1083/jcb.200202121. PMC 2173465 . PMID 11901162.
- 1 2 Hamon MA, Batsché E, Régnault B, Tham TN, Seveau S, Muchardt C, Cossart P (2007). "Histone modifications induced by a family of bacterial toxins". Proc. Natl. Acad. Sci. U.S.A. 104 (33): 13467–72. doi: 10.1073/pnas.0702729104 . PMC 1948930 . PMID 17675409.
- ↑ Decatur AL, Portnoy DA (2000). "A PEST-like sequence in listeriolysin O essential for Listeria monocytogenes pathogenicity". Science. 290 (5493): 992–5. doi:10.1126/science.290.5493.992. PMID 11062133.
- ↑ Schnupf P, Portnoy DA, Decatur AL (2006). "Phosphorylation, ubiquitination and degradation of listeriolysin O in mammalian cells: role of the PEST-like sequence". Cell. Microbiol. 8 (2): 353–64. doi: 10.1111/j.1462-5822.2005.00631.x . PMID 16441444.
- ↑ Virulence Factors of Pathogenic Bacteria. "Pathogenicity islands in Listeria: LIPI-1." State Key Laboratory for Molecular Virology and Genetic Engineering, Beijing, China. Last accessed June 18, 2007.
- ↑ Johansson J, Mandin P, Renzoni A, Chiaruttini C, Springer M, Cossart P (2002). "An RNA thermosensor controls expression of virulence genes in Listeria monocytogenes". Cell. 110 (5): 551–61. doi: 10.1016/S0092-8674(02)00905-4 . PMID 12230973.
- ↑ Grode, L. (25 August 2005). "Increased vaccine efficacy against tuberculosis of recombinant Mycobacterium bovis bacille Calmette-Guerin mutants that secrete listeriolysin". Journal of Clinical Investigation. 115 (9): 2472–2479. doi:10.1172/JCI24617. PMC 1187936 . PMID 16110326.
