Role Of Normal Microbial Flora In Human Body

Every human body are frequently comes in contact with our environment or surrounding area i.e soil, water, air, foods, anything etc. In this way your some body parts like eyes, mouth, skin, respiratory tracts and digestive tract has become resorvire for micro organisms. These such type of resorvire know as microbiome. Because in such body parts, micro organisms e.g. bacteria and yeasts are occur profusely. Now microbial flora may be two types in body, either benificial or pathogenic. In this article we’ll discuss about role of normal microbial flora in human body, that are benificial or harmful for health.

What is normal microbial flora of human body?

Bacteria and yeasts are being common parts of normal microbial flora in your body. They are widely present in both human and animals internal organs and make resident flora or commensals.

Virus and protozoa may live in human body as asymptomatic way but they are not consider as part of microbial flora. Because any viruses and protozoa species are not benificial for your body.

The number or amount of normal microbial flora may be different in every individual’s body. They also variable according to carriers or host.

Spleen, liver, blood, central nervous system, lower bronchi, alveoli and kidney are not contain any microbial flora.

What is transient flora?

Some micro organisms are potentially pathogenic for human body and may causes of infection of any disease. If such types of pathogenic micro flora present in any host even for few times then it refers as transient flora. In this case, that host or individual can be infection spreader.

What is common site for normal microbial flora in human body?

Few of normal microbial flora become dengerous for immunocompromises individual because such types or microbial flora behave as opportunistic pathogens.

Human Skin

Human skin is directly come in contact with environment and tend to favorites site for micro organisms as living site. Host’s occupation, standard of living, habitat, clothes etc are determine for colonisation of microbial flora.

Transient microbial flora easily colonise on skin. Some pathogenic hemolytic bacteria make colonies in skin of face, neck, hand and buttocks.


Generally conjunctiva is free from pathogenic microorganisms because here tears act as antimicrobial agents and continue flushing out such type of pathogenic microorganisms. But yet some bacteria are present as microbial flora in conjunctiva.

Nasopharynx and sinuses

Some bacteria are present in nasopharynx and sinuses which are act as pathogenic agents. These bacteria causes mild to serius infection in their host. Nose, throat, bronchi and lungs are common site for attacking these microorganisms.

The nasopharynx of infants is relatively free from microorganisms at birth. But ater two or three days it become full of normal commensal flora and also pathogenic organism. These normal microbial flora come from mother or nurses.


Various types of microorganisms are present in mouth. In mouth, gum pocket, crypts of tonsils, between teeth are favourite site for microbial flora. Even fungi like candida also make their colony in human oral cavity.

The mouth of infants is not free from microbes after birth. Many types of Norma flora and pathogenic microorganisms are present in mouth of infants. Basically these microorganisms comes from mother’s vagina in to mouth of infants.

Such type of pathogenic microorganisms of mouth of infants are gradually decrease after 3 to 5 days of birth. These are replacing by that type of bacteria which are occur their mother and caretaker.

Gastrointestinal tract

Normal microbial flora of gastrointestinal tract make largest symbiotic relationship with their host. These symbiotic microbes play a great role in digestion and maintain homeostasis to their host.

They also help to regulate mucosal immune system of their host. On the other hand, pathogenic microorganisms become causes of disease in GI tract and other parts. They badly affect digestive system in their host.

Genitourinary tract

Various types of pathogenic e.g doderlein’s bacilli and non pathogenic bacteria e.g E. coli and fungus e.g yeast are present in genitourinary systems of humans.

In females, vagina is more prone for microorganisms but depends upon theri pH and other enzymatic activity. pH and acidic secretion present in vagina help to from from pathogenic bacteria and other microorganisms.

What is benefits of normal microbial flora for human health?

Some bacterial microflora make symbiotic relationship with their host and provide benefits for their host. Some major benifits are following that are benificial for human health.

  • These microbial flora help in synthesis of some essential micronutrients to their host. They synthesis vitamin K and some vitamin B group.
  • These microbial flora are help in digestion undigested compound.
  • They provide local barrier against opportunistic microbes which are pathogenic for human.
  • They are improving your mucosal immune system.
  • Normal microbial flora help prevention from inflammatory diseases that are causes by colonisation by symbiotic bacteria in human.

Instead of above mentioned benifits, microbial flora play great role in improving mucosal immune system in gut. They provide threshold stimulation to immunity so that it work properly against harmful microorganisms.

What factor responsible for altering normal bacteria flora?

It is very important to make symbiotic relationship between bacteria flora and host because any factor if distrub their relationship, results in adverse effects on their host. Some are responsible factor for altering these relationships that is following-

  • Prolonged uses of antibiotics
  • Due to immunosuppressive agents
  • Due to immunodeficiency disorders
  • Alternative of ph in human body
  • Due to virulence character of symbiotic relationship and production of toxins

What is fecal microbiota transplantation?

This is a therapeutic uses of gut bacteria for chronic gastrointestinal disorders e.g irritable bowel syndrome. In this treatment methods take gut bacteria from healthy donor and introduce into patient. These complete process of infusion take places via naso gastric tube, naso duodenal tube and rectal enema. These introducing bacteria colonise in gut of patient.

What is probiotics?

Probiotics are such live microorganisms which are usually found in intestine of human. These probiotics give benifits when using it an adequate amount.

Probiotics are considering very benificial for human health. They inhibits function of other pathogenic microorganisms. The uses of probiotics in treatment of antibiotics- association diarrhoea.

Probiotics make multiple and benificial interaction with their host. They also intract with competitive inhibitors of pathogenic microorganisms or bacteria.

There are mostly two types of probiotics-

  • Bifidobacterium
  • Lactobacillus
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