A recent study investigated disruption of the microbiome in mice and a new type of poo transplant, the bacteriophage transplant.
A closer look at poo
This requires a little more explanation. In a poo transplant, (part of) the gut microbes are transferred from a healthy donor to a patient with, for example, obesity. This ensures that the disrupted microbiome of the patient is more similar to that of the healthy donor. The result: weight loss or other relief from obesity symptoms.
The effectiveness of the poo transplant has already been proven and is therefore regularly used in human health care. For example, with persistent Clostridium difficile infections in the intestines. But our intestines don't just contain a lot of bacteria. They also contain numerous viruses that target bacteria: bacteriophages. By keeping unwanted bacteria under control, these phages are partly responsible for a healthy, balanced microbiome. Bacteriophages are not only found in our microbiome by the way, but everywhere on Earth where bacteria live. It has been known for almost 100 years that they can be used as a medicine against bacterial infections.
Mice on a fat-and-phages-diet
A recent study by scientists in Denmark and the United Kingdom examined bacteriophage transplantation in mice. The process of phage transplantation is comparable to an "ordinary" poo transplant, if such a thing can be called ordinary. The big difference is that bacteria are filtered out, so that only the smallest particles, i.e. the phages, remain. The study kept different groups of mice on a "low fat" (LV) or "high fat" (HV) diet. Then, after several weeks, bacteriophages from animals on an LV diet were transplanted to a group of animals on an HV diet. These formed the treatment group "high fat + bacteriophage" (HV + bf). The results showed that the HV + bf animals resembled the LV animals in multiple ways. The weight gain of HV + bf animals decreased and both their sugar tolerance and the composition of their microbiome were more similar to that of LV animals. The expression of genes involved in energy metabolism among the HV + bf animals also increased compared to HV animals without phages. This is a sign of increased physical activity. The results are promising for potential applications in human medicine.