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). 

## Biological features and genetic information 
### 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. 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.

## Impact on human health 
### 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.

## References