Bacteroides thetaiotomicron is found in the human gastrointestinal tract (GI) as part of the normal digestive system biota, along with various yeasts. The bacterium actively targets and consumes yeast cells.
Above: Bacteroides thetaiotomicron
Bacteroides thetaiotomicron is a gram-negative, rod-shaped bacterium of the Bacteroidetes phylum. It needs no oxygen and prospers anaerobically in various environments, especially the gastrointestinal tract or "gut" of humans and other animals.
The gastrointestinal (GI) tract is the passageway of the digestive system from the mouth to the anus. The GI tract contains all major organs of the digestive system including the esophagus, stomach and intestines.
Of the 10 trillion microbes in the intestinal tract, about a billion are yeasts. The most common is Candida albicans, though not everyone has this doughty little fungus. It occurs in 40-60% of people in the Western world in the stomach, mouth, throat, vagina and/or skin.
Overgrowth of C. albicans can cause fungal infections such as:
Thrush: An overgrowth of yeast forms in mouth and throat, appearing as white, raised bumps.
Vaginitis (vaginal yeast infection): Yeast multiplies inside the vagina and causes infection. 75% of women have a yeast infection at least once, with over 50% developing it more often.
Invasive candidiasis: A severe infection of the whole body, especially bones, blood, brain and heart.
Stomach yeast overgrowth can happen due to antibiotics, steroids, oral contraceptives, meds which cause dry mouth or eliminate healthy bacteria. It can be triggered by stress, a diet rich in refined carbohydrates, sugar, or yeast; or uncontrolled diabetes, HIV, cancer or weakened immune system.
In a healthy human gastrointestinal tract, B. thetaiotomicron comprises approximately 15-30% of the total bacterial population. Its presence is crucial for balance of microbiota. It can influence physiological functions such as metabolism and immune responses.
Bacteroides thetaiotomicron is well-adapted to living in the nutrient-rich GI environment. Though digestion and excretion of nutrients, it decomposes complex carbohydrates and other macromolecules into simpler substrates more easily absorbed by the host.
While B. thetaiotomicron primarily resides in the GI tract, it's been identified in soil and marine environments. It can also be isolated from non-human animals such as cattle and rodents.
The bacteria enjoy anaerobic environments where they interact with different microorganisms. Interaction promotes development and sustainability of a varied microbiome, essential for digestive health.
In microbial history the Bacteroidetes phylum evolves alongside the emergence of complex multicellular organisms. Fossil records show bacteria have existed for billions of years. They're among the bacteria inhabiting gastrointestinal tracts of reptiles today.
The earliest mammals, tiny shrew-like creatures, appear 225 million years ago, and possibly the mammal-bacterium link is then established. Yeast is several hundred million years old and humans by comparison emerge 6 to 2 million years ago.
How Bacteroides thetaiotomicron Targets and Consumes Yeast
When B. thetaiotomicron encounters a yeast cell, it releases enzymes to break down cell walls. When the bacterium penetrates the yeast, it consumes and metabolizes the nutrients within.
The bacterium ferments yeast polysaccharides, using these sugars as a source of energy and carbon. In this process, B. thetaiotomicron excretes short-chain fatty acids (SCFAs) like acetate and butyrate, for human well-being, and as energy sources for colonic cells and colon health.
Fatty acids are shown to reduce inflammation and promote overall GI tract health. Bacteroides thetaiotomicron's ability to degrade polysaccharides gives it a competitive edge for resources.
Besides yeast hunting, B. thetaiotomicron targets carbohydrates produced by other microorganisms, adapting its weapons of choice. Enzymes enable it to digest and use diverse substrates, including innards of other bacteria. This helps control microbe populations.
Surviving the Stomach Acids
With pH between 1.5 and 3.5, the digestive system is very acidic. It contains several types of acids produced by gastric glands.
These are primarily hydrochloric acid (HCl, gastric acid) in the stomach and bile acids in the intestines. The acids help break down food and regulate the microbiota composition.
Bacteria such as Bacteroides thetaiotomicron form protective biofilms or produce acid-neutralizers such as alkaline substances. Other microbes reproduce quickly to counteract the hostile environment.
Their resilience ensures survival in the corrosive conditions of the gastrointestinal tract. Some bacteria can enter a dormant phase and resume normal function once they reach the less acidic parts of the intestines.
Yeasts also have a strong gastric acid tolerance. In low pH conditions, they modify their cell walls. Strong inorganic acids such as HCl in the stomach, and yeast cells adjusted to low pH, form an important baseline for health.
Bacteroides thetaiotomicron Facts
Nutrient Absorption: It enhances nutrient absorption by breaking down complex carbohydrates humans cannot digest alone. It influences metabolism of dietary compounds, supporting nutrition and health.
Immune Support: It helps regulate the immune system and fosters a diverse microbiome, essential for overall health.
SCFA Production: Its fermentation processes produce short chain fatty acids, which have anti-inflammatory properties and nourish the stomach lining and colonic cells.
Antimicrobial Activity: By competing with potential pathogens for resources, it helps maintain a balanced microbial community.
Immune Modulation: Bacteroides thetaiotomicron helps regulate the immune system, preventing microbial overreactions.
B. thetaiotomicron is among the most abundant bacterial species in the human GI tract, often accounting for up to 30% of the microbiome.
The bacterium has a highly adaptable genome, allowing it to respond rapidly to changes in diet and host conditions.
Enzyme Diversity: B. thetaiotomicron has one of the largest known genomes among intestinal tract bacteria, featuring genes that encode a wide range of carbohydrate-active enzymes.
Symbiotic Relationship: It establishes a symbiotic relationship with its host, providing several health benefits.
Investigations are ongoing into the potential use of Bacteroides thetaiotomicron in probiotics and personalized medicine, focusing on its role in microbiome-based therapies.
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