Bifidobacterium
Introduction
Bifidobacterium is a genus of Gram-positive bacteria that is part of the normal flora of the human gastrointestinal tract. These bacteria are anaerobic, meaning they thrive in environments without oxygen. They are also non-motile, rod-shaped, and can be found in various environments including the human body, dairy products, and the environment.
Classification and Taxonomy
Bifidobacterium belongs to the Bifidobacteriaceae family, within the Actinobacteria class. The genus was first described in 1907 by French pediatrician Henry Tissier, who isolated these bacteria from the feces of breast-fed infants. The genus Bifidobacterium now includes more than 30 recognized species, including Bifidobacterium longum, Bifidobacterium bifidum, and Bifidobacterium breve, among others.
Physiology and Metabolism
Bifidobacteria are anaerobic, but they are also aerotolerant, which means they can survive in the presence of oxygen. They metabolize carbohydrates via the bifid shunt, a unique metabolic pathway that allows them to ferment sugars more efficiently than other bacteria. This metabolic pathway produces lactic acid and acetic acid as the main end products, contributing to the acidic environment in the human gut.
Ecology
Bifidobacteria are commonly found in the gastrointestinal tract of mammals, including humans. They are one of the first types of bacteria to colonize the newborn gut, especially in infants who are breastfed. Bifidobacteria are also found in the vagina and oral cavity. In the environment, they can be found in sewage, fermented foods, and dairy products.
Role in Health and Disease
Bifidobacteria are considered beneficial bacteria. They contribute to the health of their host by inhibiting the growth of harmful bacteria, modulating the immune response, and producing vitamins such as vitamin B12 and vitamin K. They also help in the digestion of dietary fiber and other complex carbohydrates that are not digested by the host.
However, the abundance of bifidobacteria can be affected by various factors such as diet, stress, age, and antibiotic use. A decrease in bifidobacteria has been associated with various health conditions including irritable bowel syndrome, allergies, obesity, and colorectal cancer.
Use in Probiotics
Due to their health benefits, bifidobacteria are commonly used in probiotic supplements and foods. They are considered safe for consumption and have been granted the Generally Recognized as Safe (GRAS) status by the Food and Drug Administration (FDA). However, the efficacy of probiotics containing bifidobacteria can vary depending on the strain and dosage used.
Genomics
The genomes of several Bifidobacterium species have been sequenced, providing insights into their metabolism, ecology, and interactions with the host. Genomic studies have revealed the presence of genes involved in carbohydrate metabolism, stress response, and interaction with the host immune system.