Happy Thanksgiving to all our readers!

Happy Thanksgiving!

Did you know the average American microbiome is exposed to a pound of turkey on Thanskgiving.  That is almost the weight of the microbiome itself!  

In case you were expecting a nice blog write up about the turkey microbiome we are linking this review, from earlier this year, about the chicken microbiome.  Close enough, right? We will also be taking tomorrow off from writing to allow our microbiomes to fully digest our meal.  We will be back Monday though, with an all new blog.

Happy thanksgiving to you and your microbiome!

PS.  Hopefully everyone will be gobbling up antibiotic free turkey this year!

The skin microbiome and it's impact on disease

Lawrence Tynes, former kicker for the New York Giants (@AmandaTynes9)

Today’s post is going to discuss the microbiome of the largest organ in the human body, the microbiome of our skin. We talk a lot about the gut microbiome and the bacteria that are in our body, but we don’t talk nearly as much about the bacteria on our skin. Every square centimeter of our skin is home to approximately 1 million bacteria with various parts of the skin hosting different kinds of bacteria depending on how hospitable it is for specific microbes (dry or moist sites on the body).

Two scientists from the NIH published a review article last week in Science that discussed the skin microbiome and its relationship with the body’s immune system. We know that the skin microbiome and the immune system have a strong relationship in which bacteria often tells the body to undergo an immune response.  An example of this is in tissue repair. When our skin is damaged, a specific bacteria S. epidermidis results in the production of an acid that promotes wound healing.

Common skin diseases such as psoriasis, eczema, and acne are all conditions that have been linked to imbalances in our skin microbial communities. While it is not clear what initiates these conditions, better understanding the communication between the skin bacteria and our immune system will allow us to better provide a clinical benefit. In eczema patients, studies have shown that specific bacteria are more prevalent during disease flares and patients using no treatment had significantly reduced bacterial diversity at the affected site.  This tells us that it is the recalibration of the skin microbiome and not the elimination of specific bacteria that is necessary for effective treatment by reducing the inflammatory response by the immune system. 

But at this point, you’re probably wondering why Lawrence Tynes, a two-time Super Bowl champion kicker, with an IV in his arm was used as today’s image. When Larry left the Giants in 2013 for the Tampa Bay Buccaneers, he contracted something called methicillin-resistant Staphylolococcus aureus, what is commonly known as MRSA. MRSA is a specific bacterium that is resistant to several antibiotics and is therefore often very difficult to treat in patients and can lead to death. Antibiotic-resistance is a major and growing concern in today’s society that is often linked to the overuse of antibiotics. S. aureus is a bacteria that is common in our skin microbiome and is generally harmless until it becomes resistant to antibiotics.

Our skin microbiome provides an opportunity for the development of new therapies and treatments for various conditions. Because nutrients on our skin are scarce, small changes in specific nutrients can result on the composition of the skin microbiome.  Specifically, the development of creams, other topical products, as well as prebiotic and probiotic therapies could result in shifts in our skin microbiome to help combat disease. Lastly, as drug resistant bacteria continue to be a problem, it may be possible to develop therapeutics based on other microorganisms that can combat these bacteria. 

Our beneficial relationship with our virome

X-ray crystallographic structure of a Norovirus capsid.

We have been championing the virome since the inception of the AMI.  We believe that with time, viruses will prove equally as important as bacteria within the microbiome.  To this end, a paper published last week in Nature shows evidence that a specific virus can promote a healthy gut in mice the same way that bacteria do.  The virus, murine norovirus (MNV), was able to successfully restore function to mice with compromised guts.

The authors started with two groups of mice, a control group and a germ-free group.  The control group had normal guts and immune function as measured by gut morphology, and the amount of T-cells.  The germ free mice had thin, leaky guts, and low levels of T-cells.  The scientists infected these germ free mice with MNV and allowed it to proliferate.  Upon investigation of these mice, their gut integrity and immune function resembled the control group.  A second experiment was performed on mice that had been given a course of antibiotics that wiped out the normal microbiome and resulted in an abnormal immune system and compromised gut.  When these mice were infected with MNV they too saw an improvement in health.  In a final experiment mice were given pathogenic bacteria that damaged the gut, but when infected with the virus the negative effects from the pathogens were diminished.

Viruses have a bad reputation, but that’s because we generally only care about the ones that make us sick.  There are countless viruses that exist in our guts though, many that we do not interact with at all, and many symbiotic ones which have yet to be discovered.  It is time that we appreciate the entirety of our microbiome, not just the bacteria but the eukaryotes, archaea, fungi, and viruses as well.

The gut microbiome is critical to making the blood brain barrier impermeable

We have written before about the importance of the microbiome in enforcing gut impermeability.  Evidence is mounting that bacteria are crucial for preventing ‘leaky’, or permeable guts.  Leaky guts allow molecules to pass through them, which can cause many problems, especially for the immune system.  The blood brain barrier (BBB) is equally important, as it prevents toxins and molecules from entering the brain from the blood vessels.  Now, researchers have discovered the microbiome may have an equally important function towards BBB impermeability.  An article was published last week in the journal Science Translational Medicine that has shown the first link between gut bacteria and the BBB.

Researchers raised 2 groups of mice: a control group that was normally reared and had a natural gut microbiome, and a germ-free group of mice that had no gut bacteria at all.  They then tested these mice’s BBB permeability using various techniques.  The normal mice had a normal, impermeable BBB, while the germ-free mice had very permeable BBBs.  This permeability persisted, unchecked, through adulthood in the germ free mice.  However, when the researchers transplanted the microbiomes of normal mice into the guts of the germ-free mice, their BBBs very rapidly ‘tightened’ and became normal.

Gut permeability regulation by bacteria has been related to the presence of short-chained fatty acids (SCFAs), which gut bacteria produce.  The scientists wondered if these SCFAs may also have a role in regulating BBB permeability.  They fed some of the germ-free mice with SCFAs and their BBB permeability decreased and resembled the BBB of normal mice. 

This study demonstrates a new, until now, unknown function of the microbiome: it is critical to creating an impermeable BBB.  The impermeability of the BBB is essential for neuron growth and overall brain function, so this study is another in a long line that shows a healthy gut leads to a healthy brain.  

Is our virome lowering our intelligence?

We have talked about the virome and its possible substantial impact on human health on this blog before.  Lately, the virome has been getting a lot of press about its potential beneficial aspects, but today we want to discuss a negative one.  A paper was recently published in the Proceedings of the National Academy of Sciences that identified a specific virus in the virome that may be directly affecting the brain, and lowering our aptitude for spatial awareness and attention. 

Researchers were testing the oral microbiome of a cohort of people who were also taking intelligence tests as part of a separate, unrelated, study.  After genome sequencing they noticed the conspicuous existence of a virus, known as Chlorovirus ATCV-1, in about half the study population.  This virus was known to exist in algae, but had never been identified in humans, and there it was, affecting half there population.  Moreover, the virus cut across all demographics in there study, and was not related to age, race, or gender.  When the scientists compared the intelligence tests of those who had the virus versus those that did not, those that had the virus scored slightly less on tests involving spatial awareness.  However, they are quick to note that other tests for intelligence were unaffected.  They reiterate that these scores were related to the existence of the virus and not any specific demographic.

The scientists tried to recreate these results in mice.  They infected a group of mice with the virus and compared its scores on spatial tests with a control group.  The group that had the virus scored considerably lower on the tests.  When they measured specific genes that were affected in the infected mice they discovered some that related to dopamine regulation, which is known to be critical to memory formation and learning. 

Overall this fascinating study not only identified a new member of our virome, but showed that this virus may be altering our spatial reasoning abilities.  So the next time your significant other yells at you for getting lost, just blame it on your virome!

Mouth diseases and tooth loss may be caused by oral microbiome alterations

Chronic periodontitis is a prevalent inflammatory disease of the tissue around and supporting the teeth and is the leading cause of tooth loss in the United States. Scientists at the University of Florida recently published a study in Applied and Environmental Microbiology that studied the oral microbiome of 25 healthy individuals and 25 individuals with chronic periodontitis, in order to determine if there are any consistent microbial differences between the groups.

In the study, they found that patients with periodontal disease had an altered oral microbiome with microbial communitites that were more homogeneous than healthy individuals’.  They were able to identify two specific groups of bacteria, Fusobacterium and Porphyromonas, that were associated with periodontitis and another two groups of bacteria, Rothia and Streptococcus, that were prevalent in the majority of the healthy sites without periodontitis.  The scientists also identified several genes that were involved with various biological activities that were enriched in the oral microbiome of healthy individuals.

This study provides more insight into the possible microbial causes of chronic periodontitis, which is common among adults in the United States. While this study is limited because of its small sample size and its lack of diversity among severity of chronic periodontitis disease, it is still a great starting point for further inquiry into the disease. The scientists also compared their work to previous studies utilizing Human Microbiome Project (HMP) participants, though the HMP only included healthy individuals and excluded individuals with periodontal disease.  Further research could lead to the discovery of better ways to both treat and prevent the disease by altering the microbial communities of our mouth.