Bacteriophages, often abbreviated to phages, are considered to be the most numerous organisms on earth.
Wherever bacteria are found, phages will also be present.
Before the invention of antibiotics, they were used to combat bacterial infections.
However, they fell out of favor when antibiotics — which are a cheaper, easier-to-produce alternative — hit the scene.
In recent years, interest in these minuscule entities has hotted up. With teams finding increasingly vital roles for gut bacteria in both health and disease, it was only a matter of time before the importance of phages came into focus.
Bacteriophages and Parkinson's
The latest study to explore the role of phages in disease was conducted by Dr. George Tetz, Ph.D., and his team at the Human Microbiology Institute in New York City, NY.
The scientists wanted to know whether phages might influence the development of Parkinson's disease.
Aside from the motor symptoms of Parkinson's, there are often-overlooked digestive symptoms. In fact, some researchers believe that gastrointestinal dysfunction might serve as an early biomarker for the condition. However, research into Parkinson's disease and the role of the gut is a less-trodden path.
Of particular interest to the scientists were Lactococcus bacteria and the phages that destroy them. Lactococcus are thought to modify the permeability of the gut — how easy it is for nutrients and pathogens to cross from the gut into neighboring cells.
They also play a role in producing dopamine, a neurotransmitter that is key to the development of Parkinson's disease.
To investigate any potential interaction between bacteria, phages, and Parkinson's, the team analyzed the stool samples of 32 patients with Parkinson's disease and 28 controls.
Virulent Lactococcus phages
They found that Lactococcus-killing phages were much more abundant in people with Parkinson's disease, which translated into a 10-fold reduction in Lactococcus.
This loss of dopamine-producing Lactococcus could play a role in the neurodegeneration seen in Parkinson's. The researchers also found significant reductions in the levels of other common gut bacteria in Parkinson's patients, such as Streptococcus spp. and Lactobacillus spp.
"The depletion of Lactococcus due to high numbers of strictly lytic phages in [Parkinson's disease] patients might be associated with [Parkinson's] development and directly linked to dopamine decrease as well as the development of gastrointestinal symptoms of [Parkinson's]."
Dr. George Tetz
The reduction in Lactococcus seemed to be due to lytic, virulent phages — phages that destroy bacteria — of specific kinds, known as c2-like and 936 groups. Interestingly, these phages are commonly found in dairy products.
This study's findings open up new potential links between dietary and environmental factors and neurodegenerative conditions. It is too early to draw solid conclusions, and the relationship will need to be scrutinized in future work.
However, such studies give researchers plenty of trails to follow. As Dr. Tetz says, "Bacteriophages have previously been overlooked as pathogenic factors, and the study points out their pivotal role in pathogenesis."