Common foods alter gut bacteria by influencing viruses

A group of researchers has compared the idea of ​​food as a medicine. They identified certain common foods that alter our microbiome.

In today’s science, food and gut bacteria are two topics that will fuel interest and debate. Of course, the two are interdependent, and new research is focusing on some of the intricacies of this relationship.

The absence of a healthy population of gut bacteria compromises our health; the same is true when we are not following a healthy diet. However, scientists do not fully understand the exact impact of certain foods on gut bacteria.

This lack of knowledge is due, in part, to the incredible complexity of the microbiome. One factor that clouds water is bacteriophages or phages for short.

Common foods alter gut bacteria by influencing viruses

Phages are viruses that attack only bacteria. There are more viruses in the gut than dizzying gut bacteria.

Each phage attacks only a specific type of bacteria, which means that it can influence the levels of gut bacteria. Phages need bacteria to live, so if bacteria are absent, phages cannot survive.

This means that any food that influences phages can influence gut bacteria and vice versa. For example, if the population of one type of phage increases, the bacteria they consume will decrease, potentially leaving room for another species of bacteria to multiply.

In this way, viruses can affect the global microbiome – by pruning a species, they provide space for other species to fill up.

Most phages in the gut are present in a dormant form – their DNA is integrated into the genome of the bacteria. In this form, they are called prophages.

Scientists have identified certain compounds that trigger the return of prophages to their active form. When this happens, hundreds of new phages spring from the bacterial cell, killing the host and attacking other bacteria; these compounds include soy sauce, nicotine, and certain antibiotics, such as ciprofloxacin. To date, the list of phage promoter compounds is relatively short.

It is essential to find out which chemicals fuel phage activity. Because phages attack and kill bacteria, if we understand how to handle them, they could work as powerful natural antibiotics.

A recent study has attempted to expand the list of compounds that induce phage activity. Scientists at San Diego State University, CA, published their results in the journal Intestinal microbes. They hope that their results will introduce the “possibility of using a diet to intentionally organize the human intestinal microbiome via prophage induction”.

We could actually address certain conditions by adjusting the foods we eat that will affect microbial diversity, which in turn will influence health and disease.

Research Associate Lance Boling

To investigate, the researchers chose a wide range of compounds that could influence the activity of phages. They selected a range of bacteria from two common phyla in the gut: bacteroids and firmicutes. They included both beneficial and pathogenic strains of bacteria.

From 117 food compounds, they reduced their search to just 28. Researchers observed the growth of bacteria in the presence of each specific compound; they also observed its growth without the compound as a control. Then they used flow cytometry, a process sensitive enough to detect incredibly small virus particles.

Of the 28 candidates, 11 compounds produced levels of viral particles at a rate higher than that of the controls, which means that they influenced the activity of phages.

Some of the most important phage stimulants have occurred in the presence of cloves, propolis (a compound produced by bees), uva ursi (also known as kinnikinnick or bearberry) and aspartame.

The most powerful prophage inducer was stevia, which is a substitute for plant-based sugar. With certain species of bacterial strains, stevia increased the number of viral particles by more than 400%.

Conversely, certain foods reduce the number of viral particles; more specifically, it was rhubarb, fern (a type of Italian liqueur), coffee and oregano.

To complicate matters, certain compounds have stimulated the phage activity associated with certain bacteria, but reduced the phage activity linked to others; these compounds include toothpaste, grapefruit seed extract and pomegranate.

One of the most potent antibacterial foods was hot tabasco sauce, which “reduced the growth of three [gastrointestinal] except the opportunistic pathogen P. aeruginosa, on average 92%. ”

Tabasco contains vinegar, but when they tested vinegar alone, it only reduced bacterial growth by 71%. They believe that capsaicin – the spicy compound in peppers – may account for the additional antibacterial capabilities. However, in tabasco experiments, no viral particles were found, so it is unlikely that phages are involved.

These results are important. Scientists now know that the microbiome can influence our physical and mental health; it can also cause inflammation and increase cancer risk. If scientists can determine how to modify the microbiome in a specific way, they can, in theory, eliminate or reduce these risks.

As one of the authors, Forest Rohwer explains, “The ability to kill specific bacteria, without affecting others, makes these compounds very interesting.”

The new list of compounds is by no means exhaustive, of course, as Rohwer says: “There are probably thousands of compounds that would be useful in killing unwanted bacteria.”

The authors hope that scientists will continue on this path. They also explain that scientists will have to try to understand the molecular mechanisms that move the phage from inactivity to activity.

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