To us humans, this is the most exciting and potentially rewarding field that is opened up in modern microbiology. It is long been known that microorganisms populate the skin and gut and that digestion requires them. The human micro biome is the collection of microbes that colonize the human body. It consists of the 10-100 trillion symbiotic microbial cells harbored by each person, primarily bacteria in the gut and consists of the genes these cells harbor.

It seems to appear that the genome and the micro biome cross-talk, a conversation that has been continuing for billions of years with no signs of stopping. Micro biome projects worldwide have been launched with the goal of understanding the roles that these symbioses play and their impacts on human health.


For 2-3 years their micro biome grow while the immune system develops, learning not to attack the friendly bacteria. The gastrointestinal (GI) tract of a human infant provides a brand new environment for microbial colonization. Indeed, the micro biota that an infant begins to acquire depends strongly on mode of delivery. Twenty minutes after birth, the micro biota of vaginally delivered infants resembles the micro biota of their mother’s vagina, while infants delivered via Cesarean section harbor microbial communities typically found on human skin. The acquisition of micro biota continues over the first few years of life, as an infant’s GI tract micro biome begins to resemble that of an adult as early as 1 year of life. Surprisingly, the microbes that we ingest with our food might be providing our individual micro biome with new genes to digest new foods.


In recent years, it has been newly identified that, gut micro biome which is largely involved in host metabolism regulation, has been integrated into crosstalk studies between genetic factors, behavior and environmental factors as a possible contributor to obesity. It is associated with elevated energy intake and decreased energy expenditure, causing excessive fat accumulation with raised body mass index (BMI ≥ 30kg/m2), and is linked to metabolic syndrome, posing obese individuals to have a higher risk of developing obesity-associated disorders. Even more surprising is the apparent contribution of micro biome to heart disease, diabetes, and many other disorders.


Bacteria found in the mouth are more prevalent in patients with colon cancer. It seems that these bacteria protect a variety of tumor cells from being killed by immune cells. Some researchers have been exploring connections between gut bacteria and cancer for much longer. Scientists first linked the infectious bacterium Helicobacter pylori to gastric cancer back in the 1990s. And since then, other bacteria have been associated with cancer initiation and progression. Some of these microbes activate inflammatory responses and disrupt the mucus layers that protect the body from outside invaders, creating an environment that supports tumor growth. In other cases, they promote cancer survival by making cells resistant to anticancer drugs. But gut bacteria can also help fight tumors. Recently scientists have shown that some cancer treatments rely on the gut micro biome activating the immune system.


The growing area involves fecal micro biota transplantation (stool transplant) in which fecal bacteria from a healthy individual are transplanted into an infirm recipient. This has been used, for example on patients with severe gastrointestinal infections that are resistant to antibiotics. These micro biome transplants are becoming a mainstream treatment for some non-cancer illnesses. It’s still unclear exactly how microbes might interact with immunotherapeutic. A widely accepted hypothesis is that some boost the body’s response against tumors by regulating how easy it is to activate the immune system. But the precise mechanisms, including which bacteria modulate which immune cells, remain a mystery.

M.D.R Lakshan (B.Sc) University of Sri Jayewardenepura

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