You think it's your body. You touch it, see it, feel it and appreciate it. Looking at the anatomical pictures of internal parts, you feel amazed about the complexity of your body. But is everything in your body yours? Count the cells. You will realise that majority of the cells, you carry, are not yours. Those are diverse microorganisms, mostly bacteria. According to a rough estimate, a person, having 40 lakh crore cells, caries 400 lakh crore microbes. In other words, we are ten percent human. Almost three percent of our weight comes from these tiny creatures. They are present on our skin, in cavities, even in internal organs like lung and gut. The womb that was once considered to be a sterile zone, also harbours microorganisms. All this microorganisms, in our body, as a whole constitute human microbiome. A hidden world within us.
It has long been known that our gut have bacteria that help us in various ways, from providing micronutrients like vitamins to chasing out bad microbes. They are commonly called commensals. Many of these bacteria are different types of lactobacillus, similar to the one that we use to make curd. In fact, consumption of curd is an way to supplement the existing microbes within your gut. Prolonged use of antibiotics destroys microbes in the gut, even the helpful ones. That's why patients are advised to consume probiotics as supplement. Probiotics are live microorganisms that are helpful for our health.
Our microbiome is like a cocktail. It’s difficult to identify and study individual microbes in it. Now, technologies exist to identify large number of different microorganisms in a mixture, in short time, using their genetic fingerprints. Such technologies have invigorated research in this field. There is also a philosophical shift among biologists. The time of over-emphasis on genes of an individual is over. Now biologists realise that we need to take the environment into consideration to understand complexities of human physiology and diseases. The Microbiome is our immediate environment. The way we manipulate the nature around us, these microorganisms also manipulate us. And we need to understand their actions on us to maintain our health.
Take the problem of obesity. Its becoming an epidemic, even in our country. Your physician, friendly experts and the advertisements of fitness clinics must have now convinced you that our food habit and lifestyle are making us obese. Thats correct, to a large extent. But those microbes in your gut also play a role in this. Many microbes in our gut help in harvesting energy from food and affect metabolism. Therefore, variation in the microbial ecology of our gut can affect our body weight. Studies have shown that the microbiome of obese individuals is different from that of lean. In fact, one study has even shown that response to a weight-loss program has relation to individuals gut microbes. Animal studies have proved that by manipulating gut microbiome we may control obesity. One way to achieve that is to transplant a right cocktail of microorganisms in our gut. Even selective foods or antibiotics can be used to manipulate the microbial ecology. However, such works are still experimental and you have to wait some more time to add a cocktail of microbes in your fiber-rich weight-loss diet.
But experiments are not limited to obesity. Transplantation of microbes is helping in fight against a dreaded infection. Clostridium difficile is a bacteria that causes severe diarrhea, particularly in patients using antibiotics. In many cases treatment with antibiotics does not help. Loss of friendly microbes in the gut aggravate this. Infusion, made out of stool from a healthy donor, given like an enema helps in reconstructing the lost microbial world in the gut and that contains this drug-resistant disease. Such stool transplantation has been experimentally used even in other diseases like irritable bowel syndrome. Everyday, scientists are discovering connections between microbiome and other diverse diseases like asthma in children, autism, arthritis and even cardiovascular diseases. In fact many people believe that improved sanitation in the West is reducing childhood exposure to microorganisms, tweaking their microbiome and making them more susceptible to various diseases.
Our journey with microorganisms starts in the mother’s womb. The process of birth also adds, as microbes present in the vagina get transfered. In fact, microbiome of children born by cesarean delivery differs from those born by normal way. After the birth, a child's microbiome is shaped by the microbes present in mothers milk. Subsequently, it keeps changing with our food habits, environment, use of antibiotics, interactions with people and pets. The hidden world within us is dynamic and keeps interacting with us. Just like the ecosystem outside, our technology and lifestyle also affects the microbial ecology within. The biology of this ecosystem is little known. For long we have been self-centered and have written our own travelogues. Now we are learning to recognize and appreciate these invisible co-passengers of our life. Surely you will love them as much you love the mole on your cheek.