Bifidobacterium

Characteristics of Bifidobacterium

Members of the bacterial genus Bifidobacterium are gram positive, strictly anaerobic, non-spore-forming, and usually branch-shaped, rod bacteria. As this species of bacteria is primarily anaerobic and typically thrives in the absence of oxygen, the oxygen-poor environment in the large intestine makes the perfect home for them.

With more than 30 species already identified, Bifidobacterium represents one of the largest genera within the Actinobacteria phylum. This genus of bacteria was isolated in 1899 from the faeces of breast-fed babies; this fact is of particular interest as Bifidobacterium are the most common genus of bacteria found in the intestines of healthy infants. Bifidobacterium are found mainly in animals and humans.

Bifidobacterium and Breast-fed Babies

This prevalence of Bifidobacterium in the gut of breast-fed infants may be due to the ability of this species to metabolise lactose (milk sugars). In infants who are breast-fed, Bifidobacteria constitute about 90% of their intestinal bacteria; however, it is interesting to note that this number is typically lower in bottle-fed infants. The lower number of Bifidobacteria in formula-fed babies might account for the higher incidence of diarrhoea and allergies that has been noted in these babies.

While Bifidobacterium infantis, Bifidobacterium breve, and Bifidobacterium longum are the largest group of bacteria found in the intestine of infants, Bifidobacteria are said to be only the 3rd or 4th largest group in adults and comprise only 3-6% of adult faecal flora. It is noted that populations of Bifidobacteria decline quite rapidly as humans reach old age, which could account for the gastro-intestinal difficulties that are so common in older people.

Bifidobacterium and Fermentation

Bifidobacterium are known as LAB (Lactic Acid Bacteria) as they ferment carbohydrates, and produce lactic acid as a primary metabolic end product of the fermentation process. More specifically, Bifidobacteria are known to have the ability to break down oligosaccharides, complex carbohydrates made up of multiples of simple sugars such as glucose, which are often referred to as ‘prebiotics’.

The production of lactic acid by Bifidobacterium, and the resulting acidification of their environment, helps to inhibit the growth of other micro-organisms that are not conducive to their own existence or the health of their host, such as pathogenic bacteria and yeasts. The pathogens do not thrive in a low pH (acidic) environment, so this action helps to maintain a healthy balance of intestinal flora; provides protection from pathogenic intruders; helps to aid mineral absorption for the host, and may help to protect against intestinal permeability or ‘leaky gut’, a condition associated with higher levels of pathogenic micro-organisms in the intestines.

But whilst they are more commonly known for being lactic acid producers, Bifidobacteria actually produce a large amount of acetic acid, a short chain fatty acid (SCFA). Acetic acid is even more effective than lactic acid at reducing problematic yeasts and moulds in the gut environment, another factor that renders this genus of bacteria a highly desirable resident of the colon.



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Bibliography

Baffoni L.B. et al., (2013), ‘Identification of species belonging to the Bifidobacterium genus by PCR-RFLP analysis of a hsp60 gene fragment’, BMC Microbiology, 13:149.
Conlon, M. A., & Bird, A. R. (2015), ‘The Impact of Diet and Lifestyle on Gut Microbiota and Human Health’. Nutrients, 7(1), 17–44.
Lee Y., & Salminen S., (2009), ‘Handbook of Probiotics and Prebiotics’, Hoboken, New Jersey: John Wiley & Sons, pp 7-14.
Mayo, B. & van Sinderen, D., (2010), ‘Bifidobacteria: Genomics and Molecular Aspects’.Poole: Caister Academic Press.
Mitsuoka, T., (1996), ‘Intestinal flora and human health’. Asia Pacific J. Clin. Nutr., 5:2-9.
Garrity G., (1986), Bergey’s Manual of Systematic Bacteriology (Vol. 2, The Proteobacteria). Baltimore, MD: Williams & Wilkins, pp. 1418-1434.

Last updated - 15th June, 2017

 


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