Bifidobacterium

Bifidobacterium is a genus of anaerobic bacteria and a form of probiotic that is thought to have health-promoting properties for humans. Bifidobacteria are one of the major strains of bacteria that make up the gut flora, the bacteria that reside in the colon and have health benefits for their hosts. Bifidobacteria are associated with a lower incidence of allergies (Björkstén et al., 2004) and also prevent some forms of tumor growth (Guarner and Malagelada, 2003).

Bifidobacteria are normal inhabitants of the human and animal colon. Newborns, especially those that are breast-fed, are colonized with bifidobacteria within days after birth. Bifidobacteria were first isolated from the feces of breast-fed infants. The population of these bacteria in the colon appears to be relatively stable until advanced age when it appears to decline. The bifidobacteria population is influenced by a number of factors, including diet, antibiotics and stress. Bifidobacteria are gram-positive anaerobes. They are non-motile, non-spore forming and catalase-negative. They have various shapes, including short, curved rods, club-shaped rods and bifurcated Y-shaped rods. Their name is derived from the observation that they often exist in a Y-shaped or bifid form. The guanine and cytosine content of their DNA is between 54 mol% and 67mol%. They are saccharolytic organisms that produce acetic and lactic acids without generation of CO2, except during degradation of gluconate. They are also classified as lactic acid bacteria (LAB). To date, 30 species of bifidobacteria have been isolated. Bifidobacteria used as probiotics include Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium animalis, Bifidobacterium thermophilum, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis and Bifidobacterium lactis. Specific strains of bifidobacteria used as probiotics include Bifidobacterium breve strain Yakult, Bifidobacterium breve RO7O, Bifidobacterium lactis Bb12, Bifidobacterium longum RO23, Bifidobacterium bifidum RO71, Bifidobacterium infantis RO33, Bifidobacterium longum BB536 and Bifidobacterium longum SBT-2928.

The gastrointestinal tract represents a complex ecosystem in which a delicate balance exists between the intestinal microflora and the host. The microflora are principally comprised of facultative anaerobes and obligate anaerobes.

Friendly tenants in the human gut: The genome of B. longum
The microbe, called Bifidobacterium longum, is often the dominant bacterium found in humans.
The researchers identified a number of proteins specialized to help B. longum interact with the human host and persist against harmful bacteria. They can now closely look at which genes allow B. longum to live in different environments such as dairy products, vegetables and the human gastrointestinal tract.
Bacteria such as B. longum ferment sugars into lactic acid and have many health benefits. For these reasons, researchers of the food and drug industry have taken a keen interest in using these organisms.

Bifidobacterium longum lives in the human gut.

Bifidobacterium longum is among the first colonizers of the sterile digestive tract of newborns and predominate in breast-fed infants, according to the scientists. The research team isolated the bacterium from the feces of an infant. Fabrizio Arigoni, of the Swiss food and infant formula manufacturer Nestlé in Lausanne, led the study.

Other potential uses of B. longum are being investigated in separate studies. Japanese researchers showed that the microbe might be useful as a gene delivery vector for cancer therapy. They injected the bacterium into the tail veins of rats and demonstrated that B. longum is accumulated in the tumor.