Most cells in our body are not human, but microbial; the ratio of ‘them’ to ‘us’ is about 10:1. Disturbances of the interactions between host and the so-called microbiome, or simply biome, can lead to disruptions of a healthy balance. Indeed, the nature and variety of bacteria in our intestines seem to have a profound impact on many aspects of our health.

Microbes are not only essential for digesting food, but they also affect the calories we take in and they produce important enzymes and vitamins. They are also a crucial part of the immune system. In his book The Diet Myth, professor Tim Spector even suggests that bacteria are largely responsible for our obesity epidemic.

The more we discover about our relationship with our microbial inner and outer world and their role in human health, the more it seems that we live as a collective in a biological community: we are only ever a part of a dynamic ecosystem of organisms . Within this paradigm, “health” of an organism should be understood as an expression of the degree of diversity, resilience and balance of its ecosystem.

How we may maximize biodiversity in the gut is not yet entirely clear. Pre- and probiotics play a role, as do fermented and fiber-rich foods as well as a host of lifestyle factors. One self-experiment, for example, showed that a one-week diet of eating mostly potatoes had the unexpected effect of greater micro-biomic diversity.

Compared to a high-fiber diet the potato diet increased the diversity index of slightly over 26 to slightly under 39. Drastic dietary interventions, in other words, seem to have a substantial impact on the microbiome. Viewed at the level of individual bacteria, however, a mixed picture was seen. Some “good” bacteria were seen only on a potato diet. Some increased in abundance, while others decreased.

Why these apparent shifts occur is still a big question. What health effects of dietary interventions will be, and within what time frame they can be achieved, largely remains to be studied.

The microbiome-gut-brain axis

There are an estimated 200 million neurons in the intestines. This is not as much as in the brain, but more than in the peripheral nervous system and spinal cord combined. Micro-organisms appear to enter into an intimate two-way communication with these nerve cells, and these nerve cells, in turn, with the brain. This system is known as the “microbiome-gut-brain axis”.

Peripheral serotonin and the “second brain”

Serotonin is widely known as a neurotransmitter. It is also known that as much as 90% of the serotonin created in the body, is actually produced in the digestive tract. Altered levels of this “peripheral serotonin” are associated with overall health.

Research published in the leading journal Cell shows that some bacteria in the gut play a central role in regulating the production of peripheral serotonin, which suggests that changing the microbiota may help to restore the balance.

Mood-modulating soil microbes

It has been found that Mycobacterium vaccae, a common soil bacterium, has a clearly measurable effect on neurons. The bacterium is widely found in soil samples and can produce serotonin, which can affect your mood. These ground-microbes boost cytokine levels, resulting in the production of more serotonin. Gardeners inhale the bacteria and have skin contact with them. They even get them directly into their bloodstream whenever they break their skin. The natural action of serotonin-modulating soil bacteria is noticeable after approximately 3 weeks, rat experiments indicate.

The microbiome: Not only in the intestines

Although the largest amount of microbes is found in our intestines, it is also a fact that other parts of our body have their own microbiome that plays an important role in the functioning of these respective parts of the body. You may think of the skin, genitals and mouth but the eyes, external auditory canal and the nasal sinus have their own microbiome as well.

The ocular microbiome

Scientists from the School of Medicine, New York University, recently found that wearing contact lenses can change the bacterial composition on the surface of the eye significantly, possibly rendering the eye more susceptible to infection. In people who used to wear contact lenses the bacterial composition of the surface of the eye often appeared to be similar to that on the skin directly under the eyes. With contact lens-free eyes this composition was clearly different. Contact lens wearers had higher numbers of four kinds of bacteria: Lactobacillus, Acinetobacter, and Pseudomonas Methylobacterium. These microbiome disruptions could explain why contact lens wearers get more, and specific, types of eye infections.

Nasal sinus

Research by Dr. Susan Lynch of the University of California, San Diego, demonstrated that in maintaining a healthy and problem-free nasal sinus the diversity of the local microbiome plays a key role, more so than any specific pathogen. An overall healthy microbiome can keep the expression of non-desired bacterial species in check.

On her blog “lacto bacto”, Mara Silgailis writes that she herself has overcome her sinus problems by directly applying small amounts of kimchi juice to her nasal passage. She did this more than two years ago and she is still free of the sinusitis problems that plagued her in the past.

13 interesting bacteria facts

1.  Research shows that human navels contain a stunning 1,458 different species of bacteria. One person even had a specific bacterium hitherto found only in Japanese soil. This person had never been to Japan.
2. A Dutch study shows that an intimate kiss between two lovers of 10 seconds of duration results in an exchange of 80 million bacteria.
3.   In Japan a new species of bacterium was discovered that can live in hairspray.
4.   If all live bacteria in and on the surface of the body were carefully collected, the total would lie between 1.3 and 2.26 kilos.
5.   Even after thoroughly cleaning your teeth there are still 1.000 to 100.000 bacteria left behind on each tooth.
6.   The average body contains 100 trillion bacterial cells. If each cell would be equal the length of a dollar bill, this would bring you 14 times from earth to the moon and back.
7.   In any human mouth you find three times as many bacteria as the total number of people alive on earth.
8.    Bacteria are classified into three main forms: cocci (spherical), bacilli (rod-shaped) and the spirilli (spiral).
9.   The average person swallows a gallon per day of saliva, containing 100 billion bacteria.
10. Sweat does not have any smell until it is combined with bacteria on the skin.
11. Only one kilogram of C. botulinum bacteria can, depending on its distribution, wipe out all of humanity.
12  Some bacteria can move very fast: 50 to 60 times their own length in one second. This equals a 1,82 cm tall man being able to run 322 km per hour.
13. The gonorrhea bacterium is the strongest organism on earth. It can pull a force of 100,000 times its own body weight. For a man this would mean pulling 10 million kilos, or 22 fully loaded Boeing 747s.