What is gut microflora?
The collection of microorganisms resident in the gastrointestinal tract is termed as the microflora. The gut microflora contains a variety of different bacteria and fungi, of which there are typically approximately 500 different types of microorganisms with a total population of ~ 1014 (that is 100,000,000,000,000 bacteria) throughout the length of the intestinal tract.
Within particular regions the organisms may be found in three niches:
- Associated with gut wall. This can either take the form of direct attachment to the epithelium or entrapment in the mucous layer of the epithelium
- Attachment to food particles
- Suspension in the liquid phase of the gut contents.
The composition of the microflora varies in different regions of the intestine and is dependent on factors such as pH. The microflora which develops in the human intestinal tract is characteristic for that species which has evolved a symbiotic association with the host. However, a few microorganisms are only found in the human infant gut, e.g. Bifidobacterium infantis.
Before birth, the foetus is contained within a sterile environment. Within hours of birth, the baby acquires a complex collection of microorganisms which populate its oral cavity. Within days, the full length of the gastrointestinal tract will be colonised by microorganisms. The digestive tract is colonised by microorganisms the newly born infant comes into contact with, namely from the mother, father etc, milk and the immediate environment. Bifidobacterium as well as Lactobacilli will dominate the gastrointestinal tract of infants until weaning, whereby the types of microorganisms will alter in the gastrointestinal tract and will more resemble those of an adult.
At birth, babies have a very weak immune system. That system needs to be developed for survival of the infant. Breast milk, which contains nearly all the constituents necessary for growth and enhancement of the immune system, also contains beneficial bacteria which attach to the baby's intestinal wall. It is these beneficial bacteria that allow digestion in the gut to occur. As the child grows, additional microorganisms are ingested from other food sources. The fact that the microflora is not fully developed until after weaning is one of the reasons why young children are often more susceptible to illness than adults.