What bacteria are there in a healthy intestine?

There are a large number of microorganisms on the surface of human body and its cavities communicating with the outside world, such as oral cavity, nasal cavity system, throat cavity, conjunctiva, intestine, urogenital tract, etc. Some of them are long-term resident microorganisms, which are harmless when the body's defense function is normal, and are called normal flora or normal flora.

Normal flora is beneficial and necessary to human body.

Normal flora is composed of fairly fixed bacteria, which regularly settle in certain parts of the body and become a part of the body.

The number of normal flora is huge. In the long-term evolution process, through individual adaptation and natural selection, normal flora, normal flora and host, normal flora and host and different species in the environment are always in a dynamic equilibrium state, forming an interdependent and mutually restrictive system. Therefore, under normal circumstances, normal flora will not cause diseases to the host.