Listeria monocytogenes

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Listeria monocytogenes

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Bacillales; Listeriaceae; Listeria; L.monocytogenes

Species

NCBI: Taxonomy

Listeria Monocytogenes

Description and significance

Listeria monocytogenes are a Gram-positive rod-shaped bacterium that form single short chains (1), and can be resistant to the effects of freezing, drying, and heat (2) surprisingly well for a nonsporeforming bacterium. Listeria are mainly found in the soil, though Listeria monocytogenes, a pathogen, may specifically be found in raw foods, such as pasteurized fluid milk (5), raw vegetables, raw and cooked poultry (4). It has the ability to grow at low temperatures; thus, allowing it to grow in refrigerated foods. Listeria monocytogenes was thought to be exclusively associated as infections in animals, but recently, this pathogenic species has also been isolated, in its dormant form, in the intestinal tract of small percentage of the human population (3). Because Listeria monocytogenes is an agent of listeriosis, a serious disease where the overt form has a severe mortality greater than 25 percent (3), sequencing of the bacterium’s genome is of significant importance. Sequencing the genome of this organism allows for the measurement and study of traits such as new aspects regarding virulence and evolution using comparative genomics and DNA arrays (6). 16S rRNA cataloging studies have also been conducted to demonstrate Listeria monocytogenes’ close relationship to different stains of listeriae, based on genome size, GC-content and other various characters (7), which also helped place the bacterium within the bacterial phylogeny constructed by Woese (3).

Genome structure

The genome of Listeria monocytogenes strain EGD-e is just one of several stains of the bacterium that have been sequenced. Strain EGC-e is 2,944,528 base pairs long with 2853 open reading frames and a GC content of 39% (NCBI). Other strains include the genome of Listeria monocytogenes str.4b F2365, which is 2,905,310 base pairs long with a GC content of 38% (NCBI). Currently the genomes of Listeria monocytogenes str. 1/2a F6854, and Listeria monocytogenes str. 4b H7858 are being sequenced (8). Listeria monocytogenes has a single circular chromosome. The ability of Listeria to inhabit a wide range of environments is paralleled to the presence of 331 genes encoding different transport proteins, comprising 11.6% of the total gene compliment of L. monocytogenes. Listeria also has an extensive regulatory range occupying much of the total genome (8).

Cell structure and metabolism

This microbe has a unique cell membrane that contains tetraether lipids. It lacks any kind of cell wall, which causes it to have irregular shapes and is capable of assuming different shapes. The microbe uses multiple flagella for high motility. Thermoplasma volcanium is heterotrophic and therefore requires it to obtain nutrients from other organisms especially those who cannot survive in acidic or high temperature environments. Depending on its living conditions, the microbe is both anaerobic and aerobic. It is anaerobic in the presence of elemental sulfur.

Ecology

Due to its evolutionary ties to eukaryotes, Thermoplasma genus can be used as model organism for researches.

Pathology

There is no known pathogen among different strains of Thermoplasma volcanium.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen and Kit Pogliano