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23 Cards in this Set
- Front
- Back
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Hosts
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- our body contains 10 times as many bacterial cells as human cells |
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Microbiome
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- human microbiome includes microbes in mouth, skin, respiratory tract, digestive and reproductive systems |
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Examples of Microbiota Present on Body
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Skin
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- has acidic pH (pH 4-6) due to secretions of acids by oil and sweat glands. secretions are high in salt, low in water, and contain lysozyme |
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Lysozyme in Skin Secretions
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- degrades peptidoglycan, inhibiting bacterial growth |
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Skin Microflora |
- mostly Gram-positive, since they are resistant to salt and dryness |
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Common Skin Microbes
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- Staphylococcus epidermidis - Various Bacillus species - yeasts like Candida |
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Acne
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- same geneus as bacterium that makes swiss cheese - treatments include oral tetracycline or topical clindamycin to kill bacteria |
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Skin Microflora Protection from Pathogens
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- also increases acidity of the skin via bacterial fermentation of lipids (forming acetate), making it more inhospitable |
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Acquisition of Microbiome
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Microbes on Teeth
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- Microbes adhere to surfaces by forming biofilms (Streptococcus mutans and salivarius) - Acidic fermentation products demineralize teeth and cause tooth decay |
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Microbial Habitats of the Throat
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- nasopharynx and oropharynx - contains Staphylococcus aureus and epidermis |
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Microbial Habitats of the Lungs and Trachea
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Cilia in Nose
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- trap organisms entering the nasopharynx and propel them down to the acidic stomach |
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Mucociliary Elevator |
- microbes that slip into the trachea are trapped by mucus and swept upward by cilia
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Stomach Acidity
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- Stomach lining is pH 5-6 - H. pylori can resist pH 1 environment using urease to neutralize acid, but cannot grow in pH 1 - H. pylori growns instead st stomach lining where pH is more basic - half of world population has it |
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Intestine Structure
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- Pancreatic secretions (pH 10) enter the intestine and raise intestinal pH to 8, which relieves acid stress on microbes |
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Microbes in Intestine
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- Only a few resident microbes live in the small intestine; most are Gram-positive that posses salt hydrolase which allow them to grow in the presence of bile salts - colon is slightly acidic and has lower bile salt concentration, and supports a more vibrant ecosystem - intestinal lumen is anaerobic due to O2 consumption by facultive microbes - intestinal bacteria encompasses 400-500 different species as well as methanogenic archea - have special talents that allow them to build and colonize that intestinal wall - many different food sources are available to support diverse microbes |
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Effects of Different Intestinal Microbiota on Human Health
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- connection between obesity and presence of methanogens in intestines - Bacteroides thetaiotaomicron breaks down complex carbohydrates so we can absorb them - breast milk can only be broken down by specific bacteria - Encourage immune system development - Compete with pathogenic species for nutrients |
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Probiotics
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- thought to restore balance to microbial community - outcompete pathogenic bacteria - production of anti-microbials - immunomodulation |
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Fecal Microbiota Transplant
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- intestinal microbiome of a healthy person is transferred to a relative with severe intestinal disease - can relieve symptoms of IBD or colitis - also effective for patients suffering from clostridium difficile infection |
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Urinary Tract
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- Consists of Kidneys, Ureters, Urinary Bladder, Distal Urethra - Most of urinary tract is free of microbes - urethra normally contains Staphylococcus epidermis and Enterococcus species which can cause UTI if they get to bladder. |
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Vaginal Microflora
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- nutrients and pH change with menstrual cycle - acidic nature of vaginal secretion (pH 4.5) discourages growth of many microbes - acid tolerant Lactobacillus is the most populous species |
