Phocaeicola vulgatus

***Phocaeicola vulgatus***, previously known as _Bacteroides vulgatus_, is a very common bacteria found in the human gut microbiome which was first identified and described in 1932 by Arnold H. Eggerth and Bernard H. Gagnon. It is one of the most abundant species within _Bacteroidaceae_ family in the human gut, which accounts for about 30% of the bacterial population found in human faeces. _P. vulgatus_ was identified in humans all around the world, but also rarely in the companion animals such as dogs and cats. Its name, _vulgatus_, reflects such a great abundancy as from Latin it translates as "common" or "popular".

Generally _P. vulgatus_ is considered to be a beneficial bacteria due to its positive impact on digestion, however it is also known to cause infections or worsen inflammatory responses in people with suppressed immune system (opportunistic infections).

### Physiology

_P. vulgatus_ is a rod-shaped bacteria with a thin peptidoglycan cell wall sandwiched between inner and outer cell membranes (Gram negative) - a feature that impacts the classes of antibiotics that are suitable to target this bacteria. It grows in anaerobic mesophilic condtions, i.e. without oxygen in moderate temperatures (37 °C), which makes it fit to survive in human gut, but also makes it a challenge for scientists to study _P. vulgatus_ as culturing of this type of bacteria needs a strict control of conditions.

### Metabolism

In terms of nutrients, _P. vulgatus_ is capable of breaking a range of carbohydrates with glucose being a major source of energy. It also requires ammonia which provides nitrogen - another essential element for living organims. Other characteristic features of _P. vulgatus_ in terms of metabolism include:

- ability to digest complex polysaccharides into small chain fatty acids - building blocks of lipids.
- ability to convert lactate into pyruvate - essential intermediates in the metabolism of glucose to produce energy in mitochondria in the cell. This process is undertaken by the enzyme called D-lactate dehydrogenase which is encoded by the _Idh_ gene in the _P. vulgatus_ genome.
- ability to produce vitamins and bioactive compounds.

### Genomics

Some types (strains) of _P. vulgatus_ and its close relative _P. dorei_ possess a plasmid pBUN24 (a small, mobile piece of DNA) that carries genetic information encoding for a toxin BcpT which plays a vital role in colonisation of gut by this bacteria.

### Helping digestion

Studies show that _P. vulgatus_ is present in human gut from the very beggining of individual's development as it plays an important role in breaking down complex carbohydrates present in breast milk. Hence, its abundance in breastfed babieis is high.

As a human ages, _P. vulgatus_ uses metabolic pathways identified earlier to produce useful molecules for our body. It has been shown that _P. vulgatus_ is a member of a healthy gut microbiome and that it can prevent obesity from worsening. Hence, due to its beneficial properties, scientists are looking into the possible use of _P. vulgatus_ as a probiotic.

### Gut microbiome

As stated previously, _P. vulgatus_ possesses a BcpT toxin - is an antibacterial protein, which helps it to kill or stop growth of the bacteria that are its competitor for nutrients and habitat. Therefore, it has an ability to shape gut microbiome.

### Ulcerative colitis

The studies showed that people with ulcerative colitis, a disease that is characterised by inflammation inside the gut, have increased levels of oligopeptides (peptides consisting of 2-20 amino acids) in their faeces. These oligopeptides are made by digestion of proteins by enzymes called proteases, which are linked to _P. vulgatus._ Studies on mice determined that the presence of these proteases led to damage to intestinal walls, thus worsening the colitis.

However, another research that used _E. coli_ to induce ulcerative colitis in mice showed that the presence of _P. vulgatus_ reduced dicease expression via unknown mechanism. This suggests that further studies are needed to understand how _P. vulgatus_ can have a double role in the disease.

### Type 2 diabetes

Metformin is a very popular drug used to treat type 2 diabetes, however in some cases this treatment does not give any results. A recent 2025 study showed that patients who did not respond well to metformin treatment have higher levels of _P. vulgatus_ in their gut microbiome. It has been shown that the bacteria reduces the glucose-lowering effects of the drug by altering metabolic pathways and leading to a build up of ceramides in the liver- chemicals that cause increased levels of glucose in the blood.

## Role in biotechnology

Even though _P. vulgatus_ usually grows without oxygen (anaerobic conditions), it can survive in the presence of oxygen as well which makes it produce little amounts hydrogen gas. This property allows it to be used un biotechnology to test gas sensors.