The Role And Function Of Probiotic Bacteria In The Gastrointestinal Tract
Previously the focus of probiotic research was mainly on the antagonism of probiotic bacteria against enteric pathogens [1-3]. In the past decade or more, there was however a shift in focus and more emphasis is being placed on the barrier function and the stimulation of the immune system by probiotic bacteria. The following is a concise summary of recent findings regarding the role and function of probiotic bacteria in the gastrointestinal tract (GIT):
Source: “PROBIOTICS IN FOOD SAFETY AND HUMAN HEALTH”. Ed. Ipek Goktepe, Vijay K. Juneja and Mohamed Ahmedna. CRC Press. 2002. (Reference no.4).
Extract from Chapter 1: Introduction to prebiotics and probiotics (by Prof. Wilhelm Holzapfel)
A. Role of the microorganisms of the gut
“A healthy intestinal epithelium, in association with a stable intestinal microbial population, presents a vital barrier against the invasion or uptake of pathogenic microorganisms, antigens, and harmful compounds from the gut lumen”. (36) “A stable barrier, typical of healthy individuals, ensures host protection and serves as support for normal intestinal function and immunological resistance. The gut-associated lymphoid tissues (GALT) are considered to be the largest “immune organ” in the human body, and its “barriers” serve for intrinsic protection against infective agents. Around 80% of all immunoglobulin-producing cells are found in the small bowel (75), while the gut microbial population is essential for mucosal immune stimulation and amplification of immunocompetent cells (that is cells having a normal immune response)”. [4]
B. Functional properties
“Numerous beneficial functions have been suggested for probiotic bacteria:
- Nutritional benefits:
- Vitamin production, availability of minerals and trace elements;
- Production of important digestive enzymes (e.g. β-galactosidase);
- Production of β-galactosidase for alleviation of lactose intolerance.
- Barrier, restoration and antagonistic effects against:
- Infectious diarrhoea (traveller’s diarrhoea, children’s acute viral diarrhoea);
- Antibiotic-associated diarrhoea;
- Irradiation-associated diarrhoea.
- Cholesterol-lowering effects by:
- Cholesterol assimilation;
- Modification of bile salt hydrolase activities;
- Anti-oxidative effect.
- Stimulation and improvement of the immune system through:
- Strengthening of non-specific defence against infection;
- Increasing phagocytic activity of white blood cells;
- Increasing IgA production;
- Regulating the Th1/Th2 balance;
- Induction of cytokine synthesis.
- Enhancement of bowel motility and relief from constipation.
- Reduction of inflammatory or allergic reactions, by:
- Restoration of the homeostasis of the immune system;
- Regulation of cytokine synthesis.
- Adherence and colonization resistance.
- Anti-carcinogenic effects in the colon by:
- Mutagen binding;
- Inactivation of carcinogens or pro-carcinogens, or prevention of their formation;
- Modulation of metabolic activities of colonic microbes;
- Immune response.
- Maintenance of mucosal integrity.
- Anti-oxidative activities.
The major physiological functions of the gut microbial population can therefore be summarised as follows:
- Maintenance and restoration of barrier function.
- Maintenance of mucosa nutrition and circulation.
- Stimulation of the immune system.
- Improvement of the bio-availability of nutrients.
- Stimulation of bowel motility and reduction of constipation.” [4]
NOTE: All the above is directly quoted from the main source as indicated.
Other references:
- Klaenhammer, T.R.: Bacteriocins of lactic acid bacteria. Biochimie. 1988; 70:337-349.
- Vandebergh, P.A.: Lactic acid bacteria, their metabolic products and interference with microbial growth. FEMS Microbial Rev. 1993; 12: 221-239.
- De Vuyst, L., Vandamme E.J.: Antimicrobial potential of lactic acid bacteria. In: De Vuyst L., Vandamme E.J., eds. Bacteriocins of lactic acid bacteria. London: Chapman & Hall. 1994: 91-142.
- Holzapfel, W.H.: Introduction to prebiotics and probiotics. In: Ipek Goktepe, Vijay K. Juneja and Mohamed Ahmedna, eds. Probiotics infood safety and human health. CRC Press. 2006.
