Question

What is the normal biota? Where in the human body do we find it and what role, if any, does it play in human health?

Answer 1

Ans : Normal biota or normal microbiota refers to the collection of microorganisms that inhabit the human body and normally do not cause disease. They can have a symbiotic relationship with the host or commensalism (where only one is benefited) and among them only some have been well understood(which will be told in the later section). But it should be known that the human body hosts about the same number of non-human cells as that of human cells.

Inside the human body the the microbiota can be found in skin, mammary glands, placenta, seminal fluid, uterus, ovarian follicles, lung, saliva, oral mucosa, conjunctiva, biliary and gastrointestinal tracts (Gut). Among these several the Gut (gastrointestinal tract) has a major role in determining a persons health and immunity towards foreign pathogens.
some of the many functions of the microbiota that inhabits the several parts of the human body

skin- skin is a part of the innate immune system and one of the first line of defense against foreign pathogens. The human skin contains microbes that can be residential or transient that take nutrient from the sweat glands and are usually pathogenic.
conjunctiva - some bacteria and fungi reside in the conjunctiva are kept away by the  lachrymal glands continuously secreting tears that has lysozyme .

Relying upon this aspect that microorganims reside in this parts helps in easy identification by tests and as result can be treated.

this examples were non beneificial to the host but the following is an example of mutualistic relationship

Gastrointestinal Tract (Gut) - The composition of the gut microbiota is established during birth and depends upon c- section or normal delivery. Babies born through the vaginal canal have non-pathogenic, beneficial gut microbiota similar to those found in the mother. However, the gut microbiota of babies delivered by C-section harbors more pathogenic bacteria such as Escherichia coli and Staphylococcus and it takes longer to develop non-pathogenic, beneficial gut microbiota.
So the immunity of the baby hugely relies upon this aspect.

Some beneificial gut microbiota ferments dietary fiber into short chain fatty acids which are then absorbed by the host.
Intestinal bacteria helps in synthesizing vit- B & K whose dysregulation often leads to having the host several complications. Like the probiotic bacteria often medicated by doctors Lactobacillus genera helps in treating patients and improving health. Often overexposure to Antibiotic leads to killing this beneificial bacteria of the body that has hazardous implications.

Apart from this bacteria residing in the female reproductive organ gives protection against other pathogenic bacteria and ensures the health of premenopausal women.