PEDIOCOCCUS: CHARACTERISTICS, MORPHOLOGY, DISEASES - BIOLOGY - 2024

Pediococcus is a genus of gram positive bacteria that are part of the so-called "lactic acid bacteria." Their main characteristic is that they can produce lactic acid from fermentation.

It was first described in 1903 by the German botanist Peter Claussen. The genus covers a total of 10 species, among which the best known are: P. acidilactici, P. cellicola, P. clausenii and P. damnosus.

Bacteria of the genus Pediococcus are used in the manufacture of beer. Source: pixabay.com

Bacteria of the genus Pediococcus are widely known for their utility in the food industry, specifically in food preservation. They are also useful in the production of certain beers and wines, to which it provides a characteristic aroma.

In general, these bacteria are not pathogenic in man. However, in special conditions, such as when the immune system is depressed by some underlying health condition, these bacteria can cause certain pathologies. Among these, the most frequent are endocarditis and pneumonitis.

Taxonomy

The taxonomic classification of the genus Pediococcus is as follows:

Domain: Bacteria

Phylum: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Lactobacillaceae

Genus: Pediococcus

Morphology

Bacteria of this genus are spherical in shape, measuring approximately 1 micron by 2.5 microns. They are generally found forming tetrads. Single cells are extremely rare and never form chains.

Bacterial cells are not covered by a capsule. They have a cell wall that contains a thick layer of peptidoglycan, like all gram positive bacteria.

When these bacteria are grown artificially, the colonies are of average size, smooth in texture, grayish-white, and round.

General characteristics

It is gram positive

Due to the peptidoglycan that it has in its cell wall, bacteria of the genus Pediococcus adopt a violet color when subjected to Gram staining.

This is because the peptidoglycan, thanks to its structure, retains the molecules of the dye, just as it happens in all gram positive bacteria.

It is facultative anaerobic

A facultative anaerobic organism is one that can develop both in environments with oxygen availability, and in the absence of it. It can use oxygen for its breathing processes, and when it is not present, it can carry out other processes such as fermentation.

It is catalase negative

The Pediococcus genus is characterized by not possessing the genes to synthesize the catalase enzyme. For this reason, these bacteria cannot break down the hydrogen peroxide molecule (H ₂ O ₂) in water and oxygen.

It is indole negative

These bacteria are unable to separate the indole group from the amino acid tryptophan. This action is carried out by enzymes known as tryptophanases.

In the specific case of bacteria of the genus Pediococcus, they cannot synthesize these enzymes, making it impossible for them to carry out the process.

The indole test, together with the catalase test, is a very useful tool in the identification and differentiation of unknown bacteria in the laboratory.

Does not reduce nitrates

Bacteria of the genus Pediococcus do not have the genes to synthesize the enzyme nitrate reductase. This causes it to be unable to perform the reduction of nitrate molecules to nitrites.

Metabolism

The metabolism of this bacterium is based on fermentation as a process through which they obtain lactic acid. It does this from several carbohydrates, among which stand out: glucose, arabinose, cellobiose, mannose and salicin.

Taking this into account, the bacteria of the genus Pediococcus require nutritionally rich culture media with carbohydrates such as those already mentioned.

Growing conditions

In order to be grown artificially in culture media in laboratories, bacteria of this genus require certain conditions, such as a temperature range between 25 and 40 ° C. As well as a pH that can be alkaline or slightly acidic (4.5 - 7).

It is resistant to vancomycin

Vancomycin is a natural antibiotic synthesized by the bacterium Nocardia orientalis. It acts on the bacteria by inhibiting the synthesis of its cell wall. Among the bacteria that have a marked resistance to this substance are those of the genus Pediococcus.

Diseases

Under normal conditions, bacteria of the genus Pediococcus are not pathogenic to humans or other animals. However, when organic conditions change and the immune system is weakened, everything changes.

Then Pediococcus bacteria become an opportunistic pathogen and can cause disease.

Among the pathologies that can be generated in this way are endocarditis, bacteremia and pneumonitis.

Bacteremia

Bacteremia is simply the passage of bacteria into the bloodstream. By passing into the blood, the bacteria can spread throughout the body and damage certain organs.

Endocarditis

The heart is made up of three layers: the pericardium, the myocardium, and the endocardium. Endocarditis is inflammation of the endocardium, the innermost layer of the heart, due to the action of a pathogen such as a virus or bacteria.

When bacteria reach the heart in the bloodstream, they prefer the heart valves: the mitral or tricuspid (atrioventricular valves). There they fixate and colonize space.

Symptoms

• Fever
• Shaking chills
• Excessive night sweats
• Joint pain
• Chest pain when trying to breathe
• Edema in the lower limbs and abdomen
• Fatigue
• Blood in the urine
• Red spots on the soles of the feet or the palms of the hands
• Small diameter red spots that are evident on the body surface or on the sclera.

Pneumonitis

Pneumonitis is an inflammation of the lung tissue. There are specialists who consider pneumonia as a type of pneumonitis.

Symptoms

• Persistent cough
• Loss of appetite
• Involuntary weight loss
• Difficulty breathing
• Obvious fatigue and tiredness

Treatment

All bacterial infections must be treated with antibiotics. The doctor determines, through a suitable culture and a susceptibility or resistance test, which antibiotic is the most suitable.

Likewise, depending on the severity of the pathology or its progress, it may also require surgical treatment.

The important thing is to see a doctor if any of the symptoms mentioned appear.

References

1. Iwen, P., Mindru, C., Kalil, A. and Florescu, D. (2012). Pediococcus acidilactici Endocarditis Successfully Treated with Daptomycin. Journal of Clinical Microbiology. 50 (3). 1106-1108.
2. Pediococcus. Retrieved from: catalog.hardydiagnostics
3. Porto, M., Kuniyoshi, T., Azevedo, P., Vitolo, M. and Oliveira R. (2017). Pediococcus spp.: An important genus of lactic acid bacteria and pediocin producers. Biotechnology Adv. 35 (3). 361-374
4. Riebel W. and Washington, J. (1990). Clinical and Microbiologic characteristics of Journal of Clinical Microbiology. 28 (6). 1348-1355