Listeria innocua: Difference between revisions

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==Ecology==
==Ecology==
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
"Listeria" species are unusual in that they can survive and multiply at both low and high temperatures. They can also endure a wide pH range of 4.4 to 9.8 (4). These facts help explain why they are ubiquitous in all types of environment. "Listeria" spp. are found in water, soil, vegetation, wild and domesticated animals, and humans. Cultivated land has less contamination of "Listeria" than uncultivated; sandy soil contains more "Listeria" than clay-like soil; untreated sewage water is a good breeding ground for "Listeria". Since "Listeria" is also found in water sources, such as the sea, it is not surprising that fish, squids, crustaceans and other seafood have been found to contain the bacteria (8). This could be harmful for humans if the contamination is from "L. monocytogenes" because they are the pathogenic species that cause disease (5). Furthermore, human intervention, like effluents from food-processing plants, also increases the spread of "Listeria" into the environment (8).


==Pathology==
==Pathology==

Revision as of 05:40, 4 June 2007

A Microbial Biorealm page on the genus Listeria innocua

Classification

Higher order taxa:

Bacteria; Firmicutes; Bacilli; Bacillales; Listeriaceae; Listeria

Species:

Listeria innocua

Description and significance

Listeria innocua is one of the six species belonging to the genus Listeria. It is widely found in the environment (such as soil) and food sources. It can survive in extreme pH and temperature, and high salt concentration (5). In terms of appearance, it is a rod-shaped Gram-positive bacterium. It is a non-spore forming bacterium. It may live individually or organize into chains with other Listeria innocua bacteria. It is a mesophile, operating at an optimal temperature range of 30-37 degrees Celsius. Listeria innocua very much resembles its other family members, the pathogenic Listeria monocytogenes (5). Listeria innocua was isolated from meat by a technique called surface adhesion immunofluorescence (3). Samples of meat were inoculated with L. innocua and incubated at 30 degrees Celsius for 14-18 hours in a broth. The cells were then isolated from the meat by surface adhesion onto a polycarbonate membrane attached to a microscope glass slide. Then immunofluorescent microscopy was employed to visualize the bacteria (3). Listeria innocua is important because it is very similar to the food-borne pathogen L. monocytogenes but non-pathogenic in character. Thus its genome was sequenced in order to compare it to the genome of L. monocytogenes to learn what makes the former pathogenic.

Genome structure

Listeria innocua has a circular chromosome made up of 3,011,209 base pairs, with a 37% G+C content (6). Only 2,973 protein-coding genes were discovered in L. innocua, while no function could be predicted for 37% of the genes (6). The genome encodes a great variety of regulatory, surface and transport proteins (5). This explains why Listeria species can adapt to and inhabit such a wide range of environments. Listeria innocua was found to be deficient in a 10-kb virulence locus, a cluster of genes that engenders pathogenicity to Listeria monocytogenes (5). This explains why L. innocua typically does not infect humans or animals. It also has a circular plasmid of 81,905 base pairs whose function is unknown (6).

Cell structure and metabolism

Listeria innocua are Gram-positive bacteria, meaning they have a thick cell wall for protection. The cell wall is studded with hydrophilic molecules such as teichoic acids to repel hydrophobic molecules such as drugs. These organisms also produce flagella and pili for motility. Listeria innocua have very complex metabolism. They are capable of metabolizing methane, sulfur and nitrogen, among many other organic and inorganic compounds (4). These organisms also carry out numerous biosynthetic pathways, including peptidoglycan synthesis. Listeria innocua, like other members of their genus, are facultative anaerobes, which means that they can metabolism glucose (and other simple sugars) in under both aerobic and anaerobic conditions. Under the aerobic metabolism of glucose, L. innocua forms lactic acid and acetic acid. However, under anaerobic conditions, the metabolism of glucose yields only lactic acid (4).

Ecology

"Listeria" species are unusual in that they can survive and multiply at both low and high temperatures. They can also endure a wide pH range of 4.4 to 9.8 (4). These facts help explain why they are ubiquitous in all types of environment. "Listeria" spp. are found in water, soil, vegetation, wild and domesticated animals, and humans. Cultivated land has less contamination of "Listeria" than uncultivated; sandy soil contains more "Listeria" than clay-like soil; untreated sewage water is a good breeding ground for "Listeria". Since "Listeria" is also found in water sources, such as the sea, it is not surprising that fish, squids, crustaceans and other seafood have been found to contain the bacteria (8). This could be harmful for humans if the contamination is from "L. monocytogenes" because they are the pathogenic species that cause disease (5). Furthermore, human intervention, like effluents from food-processing plants, also increases the spread of "Listeria" into the environment (8).

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

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