Leuconostoc characteristics, morphology, diseases

2693
Robert Johnston

Leuconostoc is a genus of gram-positive bacteria that are found mainly in plants and dairy products. It is made up of the group of bacteria that can carry out fermentation, obtaining lactic acid as a product.

The genus was described for the first time in 1878 by the French mycologist Philippe Van Thieghem. Currently the genus includes about 16 species, of which the best known and studied is the Leuconostoc mesenteroids.

Bacteria of the genus Leuconostoc are used in the wine industry. Source: Pixabay.com

Bacteria of this genus are considered non-pathogenic for man, although infections associated with them are very rarely described..

These bacteria are very useful in certain industries such as winemaking, in which the bacteria Leuconostoc oenos It is used to carry out the fermentation process. In the same way, they are used in the food industry in the production of cheese, yogurt, pickles and sausages, among others..

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
  • 4 Diseases
    • 4.1 Endocarditis
    • 4.2 Meningitis
    • 4.3 Osteomyelitis
  • 5 Treatment
  • 6 References

Taxonomy

The taxonomic classification of the genus Leuconostoc is as follows:

Domain: Bacterium

Edge: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Leuconostocaceae

Gender: Leuconostoc

Morphology

Bacteria of the genus Leuconostoc They belong to the group of cocci, which means that they have a spherical shape, although they can sometimes adopt a lenticular shape. They have approximate measurements of 0.7-0.5 microns by 0.7-1.2 microns.

These bacterial cells are not covered by a capsule and do not produce spores..

The bacterial cell is surrounded by a cell wall whose main constituent is peptidoglycan. This is a polymer that is made up of N-acetyl-glucosamine and acetylmuranic acid. It has a great resistance and gives the characteristic shape to this bacterium.

Its DNA is contained in a single circular chromosome. In it are more than two million nucleotides. These in turn code for about 2005 different proteins. Approximately 39% of DNA is made up of guanine and cytosine nucleotides.

In the cultures they form small colonies, measuring less than 1mm. They are viscous, smooth, round and greyish in color. They grow satisfactorily in culture media rich in sucrose.

General characteristics

They are gram positive

Bacteria of this genus are Gram positive, which means that when they are subjected to the Gram staining process they acquire the characteristic violet coloration..

This is due to the presence of pepetidoglycan in the cell wall, in whose structure the dye particles are retained. It is an important property that is used to classify bacteria.

 Habitat

The natural habitat of these bacteria are plants, as well as dairy products and milk. There are some species that are mainly found in beets and sugar cane, as well as there is one species (L. oenos) that is found in wine.

They are facultative anaerobes

Bacteria of the genus Leuconostoc they are facultative anaerobes. This implies that they can grow both in the presence and in the absence of oxygen. This is important because it means that they obtain energy from a source other than oxygen and that it is not toxic to them..

Metabolism

These bacteria carry out the fermentation process, whereby glucose is fermented into lactic acid, carbon dioxide, and ethanol..

Among the compounds that these bacteria need to develop are: nicotinic acid, pantothenic acid, as well as itiamine and biotin.

They are mesophiles

The Leuconostoc It is a bacterium that to grow optimally requires being in a temperature range between 20 and 30 ° C. Above or below these temperatures, the proteins and enzymes that make up the bacteria are denatured and therefore, it dies.

It is catalase negative

It does not synthesize the enzyme catalase, so it cannot break down hydrogen peroxide into water and oxygen.

Does not reduce nitrates

Bacteria of the genus Leuconostoc they do not synthesize the enzyme nitrate reductase. Therefore they are not capable of reducing nitrates to nitrites..

It is indole negative

When they are subjected to the indole test they give a negative result. This implies that the bacteria are not able to break down the indole of the amino acid tryptophan, which is because the bacteria do not synthesize the tryptophanase enzymes..

It is Gamma hemolytic

These bacteria do not destroy red blood cells. When found in a culture on blood agar, its appearance remains intact, evidencing the absence of the hemolysis process.

Antibiotic resistance

Bacteria belonging to this genus have been shown experimentally to be highly resistant to the antibiotic Vancomycin. The reason for this has not yet been properly elucidated. It is believed to be due to some chromosomal mechanism not fully established.

Similarly, various studies have described strains of Leuconostoc also resistant to sulfonamides, cotrimoxasol, fosfomycin and fusidic acid.

Diseases

Bacteria of the genus Leuconostoc, generally, they are not known as pathogens. However, under certain circumstances it can become a causative agent of an infection.

These circumstances apply exclusively to people who have a depressed immune system, such as those who are HIV positive or who suffer from cancer..

Despite this, very isolated cases of people with bacteremia due to Leuconostoc, regardless of whether they have a properly functioning immune system.

Among the pathologies that can be caused by these bacteria, the one that has been found most frequently is endocarditis. Likewise, bacteria of the genus Leuconostoc they have also been associated with infections such as meningitis and osteomyelitis.

Endocarditis

It is defined as an inflammation of the innermost layer of the heart (endocardium), as well as of the internal structures of the heart, especially the atrium ventricular valves.

Symptoms

Among the symptoms that can be found when a person suffers from endocarditis, the following can be mentioned:

  • High fever
  • Excessive sweating, especially at night.
  • Pain in muscles and joints
  • Fatigue and weakness.
  • Incrise of cardiac frecuency.

Meningitis

It is an inflammation of the meninges. These are a set of three membranes that cover the organs of the central nervous system. Bacterial meningitis is a very careful disease and in most cases it is fatal.

Symptoms

  • High fever
  • Severe headache
  • Seizures
  • Drowsiness
  • Difficult to focus
  • Sensitivity to light
  • Nausea or vomiting
  • Neck stiffness.

Osteomyelitis

It is an infection that occurs in the bones. It occurs when bacteria reach the bone through the blood or surrounding tissue. In adults it usually affects the spine, while in children it affects the long bones of the leg and arm..

Symptoms

  • High fever
  • Mood swings: there may be lethargy and irritability.
  • Local pain
  • Edema, warmth, and redness in the affected area.

Treatment

The treatment to follow in the face of pathologies caused by bacterial agents is always the use of antibiotics. Of course, the doctor must carry out the relevant tests to determine exactly which bacteria is causing the infection..

Once this is done, you must do a study of susceptibility and resistance to the bacterial agent in order to establish the best antibiotic to treat the pathology. Antibiotics are usually given intravenously, especially when the infection is life-threatening.

References

  1. Dworkin, M., Falkow, S., Rosenberg, E., Heinz, K. and Stackebrandt, E. The Prokaryotes: A handbook on the biology bacteria.
  2. Goenaga, M., Alberdi, F., Carrera, J., Millet, M. and Garde C. (2003) Bacteremia due to Leuconostoc spp. in a patient with intestinal pseudoostruction syndrome. Annals of Internal Medicine. 20 (1).
  3. Goldman, E. and Lorrence, H. Practical handbook of microbiology. Taylor & Francis Group
  4. Hemme, D. and Foucaud, C. (2004). Leuconostoc, characteristics, use in dairy technology and prospects in functional foods. Taken from: agris.fao.org

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