General information:
Gram-positive, low G+C content, rod-shaped, non-capsulated, non-sportulating bacterium, closely related to the Bacillus group
Consisting of six species: L. monocytogenes, L. seeligeri, L. welshimeri, L. innocua, L. ivanovii, and L. grayi
Characteristics:
L. monocytogenes and L. ivanovii are typical facultative intracellular parasites, able to enter, survive and multiply inside phagocytic and nonphagocytic cells
Mode of entry: zipper mechanism
Spreads directly from cell to cell by actin-based intracellular movements
Genome Features of Listeria monocytogenes:
many putative surface proteins (internalins, LPXTG proteins, lipoproteins, GW module-containing proteins, p60-like proteins, etc.)
large number of transport proteins
many transcriptional regulators
plasmids and transposons are very rarely present in Listeria
Disease:
L. monocytogenes infects both human and aminals causing meningitis, sepsis, and abortion, L.ivanovii is restricted to sheep and cattle, in which it causes septicemic disease, neonatal sepsis and abortion, but no brain infection. The infectious disease caused by these bacteria is known as listeriosis. The other species are generally considered nonpathogenic

Comparative pathogenomics
Genomes:

L. innocua (serovar 6a) Clip 11262, 3011208 bp, NC_003212
L. monocytogenes (serotype 4a) HCC23, 2976212 bp, NC_011660
L. monocytogenes (serotype 4b) Clip81459, 2912690 bp, NC_012488
L. monocytogenes (serovar 1/2a) EGD-e, 2944528 bp, NC_003210
L. monocytogenes (serovar 4b) F2365, 2905187 bp, NC_002973
L. welshimeri (serovar 6b) SLCC5334, 2814130 bp, NC_008555
Publications:
Glaser P, et al., 2001. Comparative genomics of Listeria species. Science 294(5543):849-852.
Nelson KE, et al., 2004. Whole genome comparisons of serotype 4b and 1/2a strains of the food-borne pathogen Listeria monocytogenes reveal new insights into the core genome components of this species. Nucleic Acids Res. 32(8):2386-2395.
Hain T, et al., 2006. Whole-Genome Sequence of Listeria welshimeri Reveals Common Steps in Genome Reduction with Listeria innocua as Compared to Listeria monocytogenes. J. Bacteriol. 188(21):7405-7415.
Figures:
Schema of intracellular life cycle of pathogenic Listeria (Reproduced from: Vazquez-Boland JA, et al., 2001. Pathogenicity islands and virulence evolution in Listeria. Microbes Infect. 3(7):571-584.)

Major virulence factors in Listeria:
Actin-based motility
ActA
Adherence
Ami
FbpA
Bile resistance
BSH
Exoenzyme
Mpl
PlcA
PlcB
SMase (L. ivanovii)
Intracellular growth
Hpt
LplA1
SvpA
Invasion
Auto
InlA
InlB
LpeA
p60
Peptidase
Lsp
Regulation
PrfA
Stress protein
ClpC
ClpE
ClpP
Toxin
LLO
Pathogenicity islands in Listeria:
LIPI-1
LIPI-2
Location of virulence-associated genes in L. monocytogenes:

Terms

zipper mechanism

Entails the zippering of the host cell membrane around the bacterium as it enters. This mode of entry into non-professional phagocytes is empolyed by Yersinia pseudotuberculosis and Listeria monocytogenes. Bacterial ligand interacts with a surface molecule on the host cell. The receptor is generally a protein involved in cell adhesion and/or activation of the cytoskeleton machinery. The ligand-receptor interaction induces local rearrangements in actin cytoskeleton and other signals that culminate in the tight envelopment of the bacterial body by the plasma membrane.

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