Sangeetha Pulapaka

Most people are aware of how important it is for our well-being to have a healthy gut, which depends on a healthy gut microbiota. In fact, few things disturb our daily routines, social events or even travel experiences as the worry, pain and embarrassment of a malfunctioning intestinal system.

We even have sayings that describe how the gut can affect us: We often use our "gut feeling" to make difficult decisions, and when we are nervous of a job interview or a big examination, we have "butterflies" in our stomachs and may need to make a sudden dash to the bathroom.

Researchers are increasingly discovering and recognizing that other organ systems are influenced by the gut environment, and these links are gaining attention as possible factors in a number of diseases, such as depression and lung disease.

We may only just be beginning to discover the many ways in which a healthy or unhealthy gut can impact our lives, but we already know a lot about the important little bacteria, namely about how they impact our immune system.


This is a picture of a the intestinal cells of the colon is covered by a protective mucus layer, which some bacteria use as food. Under the microscope, this mucus layer look like small flowers.

1. Bacteria teach our immune system how to behave

The immune system is the main link between our gut bacteria and their influence on our health and disease. And we now know that this education begins even before we are born.

It was previously assumed that the prenatal environment in the womb was free from bacteria, but thanks to increasingly sophisticated analytical methods, we now know that bacteria are already present in the placenta. We are born with a naïve immune system and are at first protected by antibodies from our mother. However, the immune cells need to be educated further in order to learn how to protect the body from harm when the maternal antibodies are gone. This education is essential for our future health.

2.Bacteria educate our immune system from the moment we are born

We also know how important bacteria are for maintaining a normal immune system from experiments with germ free laboratory mice born without any bacteria at all.

These mice have an immature immune system lacking important types of immune cells. But when they are provided with even a restricted bacterial flora, the immune system matures and develops more diverse cells. These experiments have provided extensive knowledge on the function of the immune system, and of the effects of single bacteria or specific groups of bacteria.