THE HUMAN MICROBIOME
The Trillions of You
The microorganisms found in the human oral cavity have been referred to as the oral microflora, oral microbiota, or the oral microbiome. The human oral cavity contains a number of different habitats, including the teeth, gingival sulcus, tongue, cheeks, hard and soft palates, and tonsils- all of which are colonized by bacteria. There are more than 700 bacterial species detected in the mouth, and over 50% have yet to been cultivated. Only about 280 bacterial species from the oral cavity have been isolated in culture and formally named.
Researches have been utilizing cultivation-independent molecular methods such as 16s rRNA gene-based cloning in hopes of further characterizing and validating species present in the oral microbiome.
Microorganisms from the oral cavity have been shown to cause a number of oral infectious diseases, including caries (tooth decay), periodontitis (gum disease), endodontic (root canal) infections, alveolar osteitis (dry socket), and tonsillitis. [6]
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The figure above compares the proportions and oral microorganisms in the Human Oral Microbiome. [4]
Oral Flora
Vaginal Flora
Vaginal flora are the microorganisms that colonize the vagina. Discovered by the German gynecologist Albert Döderlein in 1892, vaginal microorganisms are crucial and significant to a woman's overall health.
The dominant vaginal bacterial species in women are of the genus Lactobacillus. Lactobacilli normally help to prevent long-term colonization of the vagina by adhering to vaginal epithelial cells. This usually reduces pathogens from infecting to the vaginal epithelium. This bacteria is a major contributor in creating bacteriocins, hydrogen peroxide, and lactic acid which lowers the pH of the vagina. Due to the low pH levels, the environment of the vagina is hostile and not suitable for pathogenic bacteria. [4]
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During pregnancy, the amount and diversity of the vaginal Lactobacilli is often reduced; therefore putting pregnant women at a higher risk of an infection. Symptoms associated with an imbalance in the vaginal flora include discharge, odor, irritation, redness, swelling, pain while urinating or during intercourse, burning, sensitivity and soreness.
There are many factors that can disturb the delicate balance that exists inside the vagina – some which include tissue damage caused by giving birth; stress, medication, tight clothing or synthetic underwear; inappropriate hygiene; irritants present in lotions, body washes and other cosmetic products; friction caused by penetration if the woman is not sufficiently aroused during intercourse; hormonal changes, etc. [5]
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The diagram above shows the relationship between Lactobacilli and pathogens. [3]
Gut Flora
Gut flora (gut microbiota, or gastrointestinal microbiota) is the complex community of microorganisms that live parts of the digestive tracts in the stomach and intestines. The diverse bacteria has been found to assist in digestion, metabolic activities, and can either cause or defend your body against diseases. The gut flora contains the largest numbers of bacteria and the greatest number of species compared to other areas of the body.
The composition of human gut flora changes over time with dietary changes, and as overall health changes.
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As of now, there are 3 types of classification for the gut microbiota. These types of gut microbiota have not been linked to gender, age nor ethnicity, but they show correlation between conditions and certain characteristics about a person such as obesity, metabolic rate, and etc.
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Bacteroides Gut: This type of gut microbiota has a higher concentration of the Bacteroides bacteria than any other. It is known for breaking down carbohydrates and has a possible link to obesity. Infections can be caused in areas not including the gut, and occur more commonly in people who eat meat and unsaturated fats.
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Prevotella Gut: This type of gut microbiota has a higher concentration of the Prevotella bacteria and is known for degrading slimy mucus in the gut. There is a possible link to increased gut pain and Rheumatoid arthritis, and is more common in people who consume lots of carbohydrates.
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Ruminococcus Gut: This type of gut microbiota has a higher concentration of the Ruminococcus bacteria and is responsible in helping cells absorb sugar. ​This type of gut is common in those who consume alcohol and polyunsaturated fats. [3]
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Skin Flora
The skin flora incluces all of the microorganisms on the skin of the body. A majority of the microbes are non-pathogenic. Some of the microbes are mutualistic and others are commensal. Most bacteria on the skin are found in the layers of the epidermis and the upper parts of hair follicles.
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Generally, areas of the skin that are sebaceous (fatty or oily) are more dense with bacteria and fungus. The other parts of the skin include wet and dry. The bacteria, fungus and other organisms on the body is what causes body odor. The sweat itself is odor-free. [1]
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Researches identify three main ecological areas for skin flora: sebaceous, moist, and dry.
Below are the main strains of bacteria of the skin:
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Actinobacteria (51.8%)
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Firmicutes (24.4%)
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Proteobacteria (16.5%)
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Bacteroidetes (6.3%)
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Diagram above displays virus, bacterium, and fungus in skin flora. [1]
This diagram depicts the diverse fungal makeup of the human skin. [2]
The microorganisms in the human body has an important influence on human development, physiology, immunity, and nutrition. The vast majority of these indigenous microbiota exist in a mutualistic relationship with their human host, while few are opportunistic pathogens that can cause both chronic infections and life-threatening diseases.
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