From birth, millions of bacteria begin to colonize our gut. They not only play a critical role on maintaining our physical health, but they also influence our personality. They change our emotional state, influence our memory and anxiety levels, and they even would be essential when choosing a sexual partner, as has been showed in animal studies. Without them we would not be who we are.
It sounds like science fiction, but it is real: there is a legion of millions tiny beings within you able to influence your mind without you even notice. With these discoveries, science is gradually eliminating the anthropocentric view of a self-sufficient human being, with total control over their mental functions. We do not live alone. Millions of nonpathogenic bacteria are with us from birth and without them nothing would be the same. They all together form our microbiota.
They are known to be essential for developing good defenses and to digest certain foods. But in addition, they are able to communicate with our brain. They influence on individuals’ social behavior and partner choice, food selections; they can modify our memory, learning process and mood.
All our skin is coated by these bacteria, but they accumulate largely in the intestine. Like in a great megalopolis of microorganisms, several million of them live in our warm and comfortable digestive tract inside.
Bacteria to fall in love
“There is increasing evidence that microbiota is involved in certain social behaviors such as kin recognition and reproductive behavior,” explains Zenobia Lewis, researcher at the University of Liverpool, UK.
Her studies with flies reveal how gut microbes can influence mate choice. The fly is able to identify family members by the composition of its flora and avoid inbreeding. “In insects, this gut microbiota effect appears to be related pheromones production. What it is eaten, affects stomach bacteria, and therefore the host’s odor. For many animals, the smell is essential for deciding to pair with another individual,” Lewis explains.
In short, a fly accept only be reproduced with another if its microbiota exhale the right scent. This phenomenon is not unique to insects. Other studies have shown similar effects in primates. According to Lewis, “not even humans seem to be immune to the effects of the microbiota. It is suspected that bacteria from our armpits influence when choosing bedfellow!”
The consequences of choosing sexual partners depending on which organisms live within him or her, may determine the course of evolution in the long run, leading to the emergence of several species where before there was only one.
A group headed by Pacheco Lopez, researcher at the Metropolitan Autonomous University (UAM) in Mexico City, also studies how microorganisms in the intestines can change social behavior. He believes that the human being should be considered as a complex organism, which cannot act independently of its closest companions.
Tell me what bacteria you have and I’ll tell you who you are
It is already quite surprising that bacteria plays a role when choosing with whom having offspring; but they also send signals to the brain that may modulate host’s mood, levels of anxiety, learning performance, or pain feeling. Microbiota has also been related with diseases like autism or multiple sclerosis.
“There is evidence that gut bacteria influence in mice’s memory and behavior. Furthermore, it has been found that the microbiota is involved in anxiety levels “. Some studies show that the stress response in mice that have grown completely free of microorganisms is abnormally high. These animals also perform worse on tests of simple memory.
Another way to investigate the effect of these guests is to colonize the digestive tract of a rodent strain with other’s microbiota. For this, feces bacteria are removed from a donor and introduced into a receiver, which results in behavior changes, becoming similar to the donor.
Brain and microbiota are in contact
It is not necessary a stool transplant to modify the gut microbiota. Probiotics are bacterial tourists: living organisms that are managed from the outside and can produce a benefit to the host. If the appropriate bacterial species were known, it would be possible to giving probiotics cocktails to improve mood and stress in people with certain diseases.
The easiest way to modify the bacteria population is our diet; from childhood, it can promote the growth of some or other microorganisms.
So, these legions of tiny guests are standing in the spotlight for the development of therapies against neuropsychological diseases. But although it is increasingly clear that the conditions of the brain can be modified by modulating the intestinal microbiota, as John Cryan, researcher at the University of Cork (Ireland), said: “This leading to therapies based on microorganisms is still only a tantalizing possibility worth investigating.”
Messages of microorganisms reach the brain through molecules that activate the vagus nerve –which carries information from our internal organs to the brain — or act on the immune system. Both channels are used to transfer information to the central nervous system.
This messaging is reciprocated, since the brain also sends information that modifies the composition of the microbiota. Stressful situations in childhood may vary microbiome for life, as well as chronic stress in adults. For example, a mouse that has been separated from his mother three hours daily during the first twelve days of life has a different microbiota than one who has not experienced this trauma.
Butterflies in the stomach
The truth is that it is not surprising that there is a continuous communication between the gut and the brain; many feelings or mental states are reflected in our guts. We feel butterflies in our stomach when we fall in love; and we also feel that our stomach closes, if we are nervous.
Our feelings are reflected in the digestive tract and vice versa, affecting our mood; because in the gut there is a network of several hundred billion neurons, which act independently of the brain. This network of intestinal nerve cells is in close contact with the population of microorganisms in the human body, about 100 trillion bacteria. This is why the gut has gained the name of ‘second brain’.
Source: Agencia SINC