BIFIDOBACTERIUM: CHARACTERISTICS, REPRODUCTION, NUTRITION, BENEFITS - BIOLOGY - 2025

Bifidobacterium is a genus of bacteria of the Actinobacteria class that groups together species that are characterized by being Gram positive, lacking a flagellum, and being usually branched and anaerobic. They are one of the main groups of bacteria that make up the gastrointestinal flora of mammals, including man.

These bacteria were identified for the first time in 1899 by the French pediatrician Henri Tissier, who isolated them from the intestinal flora of infants and, until 1960, it was believed that they all belonged to the same species, called Lactobacillus bifidus. Currently the genus Bifidobacterium groups more than 30 valid species.

Microscopy image of adolescent Bifidobacterium. Taken and edited from: Y tambe.

Some species of the genus are used as probiotics, that is, microorganisms that when ingested are capable of altering the intestinal flora, promoting benefits for the health of those who eat them.

Among the benefits of using Bifidobacterium as probiotics is the fact that it helps in peristaltic movements of the intestine. It also helps combat the side effects of Helicobacter pylori treatment, such as diarrhea and halitosis.

General characteristics

Bacteria of the genus Bifidobacterium have a characteristic Y shape, which gives rise to the name of the group (bifid bacteria). All of them are Gram positive, that is, they are stained violet by the Gram stain method.

Until recent years, researchers considered that all bifidobacteria were strictly anaerobic, however, the discovery and description of new species of the genus has shown that they have different levels of tolerance to oxygen.

Depending on this tolerance, nowadays Bifidobacterium are classified into four groups: bacteria that are hypersensitive to O ₂, sensitive to O ₂, aerotolerant and microaerophilic.

They are part of the group of so-called lactic acid bacteria, that is to say, of those bacteria whose main terminal product of carbohydrate fermentation is lactic acid.

All of them are non-mobile due to the lack of flagella.

The genome of the members of this genus ranges between 1.73 and 3.25 Mb, with about 15% of the genes associated with the encoding of enzymes involved in carbohydrate metabolism.

Bifidobacteria are widely distributed in the gastrointestinal tract, vagina, and mouth of mammals, including humans. Scientists have also isolated some species from the gastrointestinal tract of birds and insects.

Taxonomy

These bacteria are taxonomically located in the phylum Actinobacteria, class Actinobacteria, order Bifidobacteriales, family Bifidobacteriaceae. Bifidobacteria were first isolated in 1899 by Dr. Tissier of the Institut Pasteur in France, and he called them bifida because of their characteristic shape.

Despite the fact that the genus Bifidobacterium was established by Orla-Jensen in 1924, until 1960 all bifidobacteria were considered as a single species belonging to the genus Lactobacillus (L. bifidus).

Currently 32 species of Bifidobacterium are recognized, many of them identified based on genome sequencing.

Reproduction

Bacteria of the genus Bifidobacterium all reproduce by binary fission. This is a process of asexual reproduction that begins with the replication of genetic material, which consists of a single circular double-stranded DNA chromosome.

After the replication of the chromosome, each copy is located in one pole of the bacterial cell, the division of the cytoplasm begins and the formation of a septum that will separate the cytoplasm into two compartments, this process is called cytokinesis.

At the end of the cell wall and membrane formation in the septum, two smaller daughter cells originate, which then grow and can again enter the fission process.

Nutrition

Bifidobacteria are mostly commensals in the intestinal tract of mammals and other organisms, there they help digestion of high molecular weight carbohydrates, degrading them to smaller molecules that can be assimilated by them, by other bacteria as well as by their hosts.

Humans, as well as other metazoans, are unable to digest some polysaccharides, while bacteria are, because they are capable of synthesizing enzymes, such as fructanases, which are capable of acting by breaking the bonds that make up polysaccharides called fructans.

Electron microscopy image of Bifidobacterium longum. Taken and edited from: Julie6301.

Fructan is the generic name for different fructose polymers that are part of the reserve material of a wide variety of plants.

Foods with bifidobacteria

Bifidobacteria belong to the group of lactic acid bacteria, that is, bacteria that produce lactic acid as a result of carbohydrate fermentation. The foods that contain Bifidobacterium are mainly dairy products and their derivatives.

These foods include cheeses, yogurt, and kefir. The latter is a product similar to yogurt, which is obtained by fermenting milk with yeast and bacteria. It is a food native to Eastern Europe and Southwest Asia and contains higher amounts of probiotics than yogurt.

Mechanism of action as probiotics

First of all, the bifidobacteria nutrition process helps the digestion of sugars that are indigestible for humans directly, degrading them and releasing nutrients that can be assimilated by their host.

Second, the lactic acid product of the metabolism of bifidobacteria helps to lower the pH of the gastrointestinal tract, which prevents the proliferation of Gram negative bacteria that can be dangerous to health.

Health benefits

The importance of the presence of bifidobacteria in the gastrointestinal tract for human health has been known to researchers since the beginning of the last century. Indeed, as early as 1907, the then director of the Pasteur Institute, Elie Metchnikoff, proposed the theory that lactic acid bacteria were beneficial for human health.

Metchnikoff based his theory on the fact that the longevity of Bulgarian farmers seemed to be related to the consumption of fermented dairy products. Due to this, this microbiologist suggested the oral application of fermentative bacteria cultures to implant themselves in the intestinal tract, carrying out their beneficial action.

The presence of bifidobacteria in the gastrointestinal tract helps in the digestion process of carbohydrates, and is also associated with a lower frequency of allergies. Currently some species of Bifidobacterium are generally considered safe and used as probiotics by the food industry.

According to the Natural Medicines Comprehensive Database, the use of these bacteria as probiotics is probably safe to treat some disorders such as:

Constipation

Constipation is the difficulty to perform bowel movements, which are generally fewer than three times a week, with excessive effort, pain and with the sensation of incomplete bowel movements. It can be associated with different factors such as a low fiber diet, diabetes, stress, depression, heart or thyroid disease, among others.

Clinical trials have shown that adding Bifidobacterium to the diet helps increase bowel movements, significantly increasing the number of weekly bowel movements in patients. However, this result may vary depending on the strain of bifidobacteria used.

Food with bifidobacteria. 90 grams of kefir grains on a plate. Taken and edited from: Webaware.

Infection by

Helicobacter pylori is a Gram negative bacterium characterized by having a helical shape, hence the name of the genus. It lives exclusively in the gastrointestinal tract of humans and can cause various diseases such as gastritis, peptic ulcer and lymphoma of the lymphoid tissue associated with the mucosa.

Treatment for H. pylori infection includes two different varieties of antibiotics to prevent the development of resistance, as well as antacids to help re-establish the lining of the stomach walls. This treatment can have side effects such as diarrhea and halitosis.

In addition, antibiotics act both against H. pylori and against the other bacteria present. If the treatment is accompanied by the ingestion of bifidobacteria and lactobacilli, the side effects of the treatment are reduced. The intestinal tract is also prevented from being recolonized by Gram negative bacteria.

Diarrhea

Rotaviruses are non-enveloped, two-capsid, wheel-shaped viruses that can cause an illness characterized by vomiting and watery diarrhea in infants for 3 to 8 days. Administration of bifidobacteria can reduce the duration of this type of diarrhea.

Likewise, if bifidobacteria is ingested together with lactobacillus or streptococcus, it can prevent traveler's diarrhea, which is a mild infection caused by bacteria that have contaminated water or poorly handled food.

Pouchitis or pouchitis

Pouchitis is a nonspecific inflammation of the ileoanal reservoir of unknown cause, although the fecal flora plays an important role in its development. It affects patients who have undergone panproctocolectomy and causes a great deterioration in their quality of life.

Different clinical trials have yielded enough evidence to show that the intake of probiotics composed of bifidobacteria, lactobacilli, with or without streptococci helps prevent the appearance of this inflammation.

Respiratory tract infections

The regular intake of probiotics containing bifidobacteria helps to strengthen the immune system of healthy people thus preventing the appearance of respiratory tract infections, however, it does not help prevent hospital infections in infants and adolescents.

Other diseases

There are a considerable number of other diseases for which it has been suggested that taking Bifidobacterium would have beneficial effects, but for which there is insufficient scientific evidence to support such claims. These include eczema, drug diarrhea, bipolar disorder, and diabetes.

Nor can it be assured that it is effective in treating celiac disease, arthritis, slowing aging, preventing chemotherapy-related infections, controlling cholesterol levels, and other diseases.

References

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