The Microbiome – How Bacteria Rule Over Your Body
Voice of Biotecnika – Episode No: 56
Humans are considered as the most powerful species on earth. They are the most intelligent and have the power to control everything that exists on earth. But what, if we tell you, that this super-intelligent human race is controlled by tiny organisms that live within or exists inside the human body. They not only influence the human brain but behavior too.
Scary right! Welcome to the next episode of Voice of Biotecnika, where we will tell you about who these tiny organisms are and why as well as how these tiny organisms control humans or more precisely “RULE OVER YOUR BODY”.
Bacteria are everywhere, the air you breathe, the water you drink, food that you eat, on and inside your body, things you use like mobile phones, laptops, tabs, even washed clothes as well as utensils, everywhere, you can think about it. In recent years, the term “microbiome” has sought the attention of researchers and scientists all-round the globe. So you must be thinking what is this Microbiome? Microbiome describes the genome of all microorganisms including bacteria, viruses, fungi and archaea in a particular environment, like the microorganisms in our gut environment are known as the gut microbiome. These microbes can be symbiotic or pathogenic, living in and on all vertebrates.
Talking about bacteria in the gut, these are key to many aspects of human health including metabolism, immune, and neurobehavioural traits which have been supported by evidence from the animal models and human studies. But how our relationship with these bacteria begins? It is assumed that humans develop their relationship with bacteria inside the mother’s womb. The innumerable bacteria present inside the mother’s womb, cover every single part of our body. Pregnant mothers release some molecules that make their way in the fetal brain and seed their babies with these microbes during childbirth. After birth, special sugars that are present inside the mother’s milk feed and support these bacteria. During the first few years of infant life, both the brain and microbe rapidly develop. These bacteria help in the development of our immune system and develop a healthy community inside the human body. Once the solid diet is introduced to babies, it becomes an important factor that has a stronger impact on subsequent maintenance and maturation of gut microbiota organization throughout the lifespan. These bacteria are considered to play an important part in human health, therefore, our body not only accepts their invasion but we also welcome it.
What does this gut microbiota do for us?
There are several categories of bacteria inside our bodies. There are some whom we learn to live, the one which is present in our mouth and can harm our teeth if we do not brush daily. Next is, friendly fellows who live in our gut. The bacterial microbial communities present in the human gut are essential for maintaining the intestinal ecosystem as well as play an important role in gathering energy from foods and producing micronutrients. The gut microbiota performs fermentation of non-digestible substrates like dietary fibers which in turn supports the growth of short-chain fatty acids and gases producing microbes. Several enzymes produced by these gut microbes contribute to the metabolism of bile acid that acts as metabolic regulators and signaling molecules to affect important pathways in the host. In return, we provide food to them and an appropriate environment for growth. Thus, we not only live with them but also depend on this vast army of bacteria to stay alive.
Every human has a distinctive microbiome. In the last few years, understanding of the influence of gut microbiome goes much deeper. The gut microbiome is considered an area of great assurance for a better understanding of human health and related diseases. It is considered that the bacteria that are part of our microbiome encodes millions of genes that can manufacture thousands of metabolites, which has the potential to replace many of the functions in the host which affect the host’s phenotype, fitness, as well as health. Whether it’s a craving for a specific food, immune system protection, regulation of behavior or role in several disorders such as depression, autism, dementia, and many others, in all these, our body’s bacterial community plays a very important role. Therefore, the microbiome is now considered a virtual organ of the human body.
So, how do these microbiomes communicate with us?
There are several pieces of evidence that indicate the human immune system and microbes communicate with each other and produce a specific response. Different disease results in changing of the composition of these bacteria in the gut. Several researchers are working on how our body’s immune system interacts with these tiny travelers and how that relationship may function in a particular disease. For example, certain bacteria that are present in the lining of the gut excrete excessive quantities of antibodies into the gut, which can help in understanding what are the antibodies types being made, and how the body tries to regulate the interaction between ourselves and bacteria on the outside.
It is interesting to know that microbes can even talk to our brain, they not only interact but affect our nervous system or maybe our mood too. In the gut, several neuroactive compounds are synthesized which have a major impact on mental well-being. Studies have reported the production of DOPAC, a metabolite of the neurotransmitter dopamine in humans is related to the healthier mental quality of life. Dopamine and serotonin have composite roles in the brain and imbalances related to it. About 90% of serotonin which is an important messenger for the immune system, produced in the gut. Scientists believe that the microbiome does this to communicate with the vagus nerve, which connects about 100 million nerve cells from the digestive tract to the base of the brain. The vagus nerve sends these signals from the gut to the brain, where they alter the production of a hormone called oxytocin that promotes social bonds. Some chemicals communicate through the bloodstream with the brain. Since the brain decides what to eat, the microbe is interested in a healthy brain.
Bacteria in the gut have the ability to manage behavior and mood through altering the neural signals in the vagus nerve, changing taste receptors, producing toxins to make us feel bad, and liberating chemicals to make us feel good. However, the microbes, that live outside the human body, like those present in the soil are not able to synthesize some kind of neurotransmitters. The reason might be that these microorganisms have not co-evolve with humans and therefore, have not learned to gain advantage from invading into the host nervous system.
Although there is a heritable part of gut microbiota, several environmental factors such as related to diet and drugs decide the composition of gut microbiota which in turn can affect our health. Antibiotics entered indirectly in our body through the food chain have various metabolic consequences that vary from person to person. Antibiotics are used for livestock farming in many countries. Several human studies, as well as many rodents studies, have provided an obesogenic effect of antibiotics in humans in minute doses found in food. Therefore, extensive research on the gut microbiome is required to better understand the effect of antibiotics, chemicals such as pesticides sprayed on crops on them.
Several animal studies have shown that sugar substitutes such as aspartame, sucralose as well as saccharin and food additives such as emulsifiers which are present in processed food have negative effects on the animals’ gut microbiota. The production of trimethylamine from carnitine and dietary phosphatidylcholine (dairy and meat products) by gut microbiota varies between people depending on the food they consume. This trimethylamine oxidized in the liver to trimethylamine N-oxide, which is associated with an increased risk of atherosclerosis (buildup of plaque inside arteries) and major adverse cardiovascular events. Some people follow restrictive diets like raw food, the vegan, gluten-free diet which may also raise some concern as these may have some side-effects on gut health. So, there is a strong relationship in what you eat decides what type of bacteria you breed or what type of bacteria present in your body decides what to eat.
These microbes initially come from our mother but how they develop and change depending on what we eat. For example, some bacteria like fibers whereas some like cheese. If we eat a lot of fast food we breed fast food-loving bacteria that take up space for vegetable eating bacteria and also send signals to the brain to eat fast food. Thus, gut microbiota seems to play an important role in the development and progression of obesity. So we can reverse fast food or cheese liking bacteria with vegetable liking or fiber good bacteria and this intensifies the strong connection between diet and microbiome.
Also, it’s not just about the bacterial numbers but their diversity too. It has been observed that the people suffering from inflammatory bowel disease, type 1 or 2 diabetes, obesity, and atopic eczema have lower bacterial diversity than in healthy individuals. This indicates that the gut ecosystem which is rich in microbe species is more robust against environmental influences. If any microbe species is missing, its function is been performed by a more related microbe. Thus, “diversity” seems to be a good indicator of a “healthy gut”. However, an increase in dietary fiber or a specific type of diet may temporarily reduce the diversity as the microbes related to digestion of fibers increases, leading to change in a composition via competitive interactions. It has been reported that the people who lack certain bacteria in their gut are more likely to undergo depression. Studies have provided evidence that the bacteria Dialister and Coprococcus, were uncommon in depressed people. It might be possible that the people suffering from depression may have different eating habits that have led to changes in their gut flora, resulting in their low levels and in turn responsible for depression.
Some researchers also believe that bacteria living within our bodies may cause stomach or other cancers. Thus, the evolution of tumors and bacterial communities are linked. There are several pieces of evidence where minor changes in microbiota can result in major changes in immune-chemotherapy treated cancer patients, autoimmune disorders and bone marrow recipients. For example, studies have shown that phytoestrogens have a protective effect on breast cancer which depends on the presence of several intestinal bacteria such as Lactonifactor longoviformis, Clostridium saccharogumia, and Blautia producta, Eggerthella lenta that can convert isoflavones into bioactive compounds. Targeting the microbiome, there is a possibility for preventing a variety of diseases such as diabetes and gastrointestinal tract cancers. The treatment is possible by using probiotics that increase the populations in gut treatment.
Probiotics are live microorganisms that when given in an appropriate amount have health benefits on the host. Among probiotics, mostly Lactobacillus species and Bifidobacterium species are included in of products such as dietary supplements, drugs, and food. There are concerns that most microbe supplements are unable to set themselves in the gut and in turn, do not exert any effect on the resident community. However, they have a direct effect on the host through the production of bioactive compounds or immune modulation. But, prior to probiotic treatment, it is important to know about the substances synthesized by these bacteria followed by their testing. This is a challenging task as this diverse and complex bacterial community of gut microbiome keeps on changing during different stages of life. The human microbiota undergoes the most prominent fluctuations during infancy and old age. This is the time when our immune health is most unstable and weakest. The elderly people have different bacterial gut microbiota profile than healthy adults. There are evidence that suggests, the association of gut microbiota with age-related chronic conditions of health and inflammation, and hence could be exploited as a presumed target to improve the aging process.
Understanding the functional role of the human gut microbiome, the researchers have come up with fecal microbiota transplantation. It’s not yet clinical practice but has been explored where feces from a healthy donor is transplanted to recipients with metabolic syndrome resulting in better insulin sensitivity. Fecal microbiota transplantation (FMT) provides support in the treatment of recurrent Clostridium difficile infection with cure rates reported up to 90% in clinical trials. However, the FMT use in other conditions such as obesity, inflammatory bowel disease, metabolic syndrome, and functional gastrointestinal disorders is still controversial. Thus, more studies are required to fill in gaps in understanding microbiome composition, function and bacterial prebiotics, probiotics or fecal microbiota transplantation to assess changes in microbiota composition and in health outcomes. The extensive catalog of human gut bugs will help scientists to recognize the specific bacteria in patients’ bodies and lead research into new treatments for conditions such as psychiatric, neurological, allergies, obesity, aging, bowel syndrome and many disorders.
So, now you might have understood better, that your diet plays an important role in the development of healthy bacteria inside your body. Your microbiome not only indicates what is going inside you but also keeps you healthy as well as happy, because after all it’s not you but your “microbiome- that rule over your body”.