Podcast
Questions and Answers
What role does gut microbiota play in the immune system function?
What role does gut microbiota play in the immune system function?
What is colonization resistance?
What is colonization resistance?
What occurs when antibiotics disrupt the gut microbiota?
What occurs when antibiotics disrupt the gut microbiota?
Which factor can lead to the normal flora becoming pathogenic?
Which factor can lead to the normal flora becoming pathogenic?
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What harmful effect can result from harmless food substances processed by gut bacteria?
What harmful effect can result from harmless food substances processed by gut bacteria?
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What is the primary function of tears, mucus, and oil in the context of the eye?
What is the primary function of tears, mucus, and oil in the context of the eye?
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Which statement about the normal flora in the ears is correct?
Which statement about the normal flora in the ears is correct?
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Which microorganism is commonly found in the nasopharynx and can cause pneumonia in immune-compromised individuals?
Which microorganism is commonly found in the nasopharynx and can cause pneumonia in immune-compromised individuals?
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Where in the gastrointestinal tract is the majority of bacteria found?
Where in the gastrointestinal tract is the majority of bacteria found?
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What opportunistic infection can occur if E. coli moves from the gastrointestinal tract to the urinary tract?
What opportunistic infection can occur if E. coli moves from the gastrointestinal tract to the urinary tract?
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In the oral cavity, which type of bacteria is most commonly associated with dental caries?
In the oral cavity, which type of bacteria is most commonly associated with dental caries?
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Which part of the urinary tract is typically sterile?
Which part of the urinary tract is typically sterile?
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What type of bacteria primarily colonizes the vagina?
What type of bacteria primarily colonizes the vagina?
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What is the primary reason transient microbiota do not establish long-term residence on human skin?
What is the primary reason transient microbiota do not establish long-term residence on human skin?
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Which of the following locations is NOT typically associated with the presence of resident microbiota?
Which of the following locations is NOT typically associated with the presence of resident microbiota?
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Which of the following statements is true about resident microbiota on the skin?
Which of the following statements is true about resident microbiota on the skin?
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Which of the following is a characteristic of the skin microbiota?
Which of the following is a characteristic of the skin microbiota?
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In which of the following conditions are transient microbiota most likely to thrive?
In which of the following conditions are transient microbiota most likely to thrive?
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What primarily influences the survival of transient microorganisms on human skin?
What primarily influences the survival of transient microorganisms on human skin?
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Which of the following microbes predominantly accounts for the normal flora of the skin?
Which of the following microbes predominantly accounts for the normal flora of the skin?
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Which of the following is NOT a factor in the temporary nature of transient microbiota?
Which of the following is NOT a factor in the temporary nature of transient microbiota?
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What is the primary composition of gut microbiota?
What is the primary composition of gut microbiota?
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What is the weight of the gut microbiota approximately?
What is the weight of the gut microbiota approximately?
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Which microbiota is known to potentially cause infections when resident microbiota are reduced?
Which microbiota is known to potentially cause infections when resident microbiota are reduced?
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What role do commensals or normal microbiota play in the body?
What role do commensals or normal microbiota play in the body?
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Which of the following factors does NOT affect the composition of microbiota in humans?
Which of the following factors does NOT affect the composition of microbiota in humans?
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Which of the following organs is sterile under normal conditions?
Which of the following organs is sterile under normal conditions?
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How many different species of microbes are roughly estimated to inhabit the human body?
How many different species of microbes are roughly estimated to inhabit the human body?
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When does the formation of human body microbiota typically begin?
When does the formation of human body microbiota typically begin?
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What role does normal flora play in the vagina?
What role does normal flora play in the vagina?
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Which of the following statements about the microbiome is true?
Which of the following statements about the microbiome is true?
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How does microbiota benefit newborns specifically?
How does microbiota benefit newborns specifically?
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Which bacteria is associated with fungal vaginitis?
Which bacteria is associated with fungal vaginitis?
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In patients with inflammatory bowel diseases, which genera are found in greater numbers?
In patients with inflammatory bowel diseases, which genera are found in greater numbers?
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What does intestinal microbiota provide that is essential for digestion?
What does intestinal microbiota provide that is essential for digestion?
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What is a protective function of normal flora in the body?
What is a protective function of normal flora in the body?
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What effect did fecal bacteria from obese mice have when transplanted into germ-free nonobese mice?
What effect did fecal bacteria from obese mice have when transplanted into germ-free nonobese mice?
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Study Notes
Microbiota
- Microbiota are microorganisms, primarily bacteria, fungi, protozoa, and viruses, that live in the human body.
- They are essential for the human body, and are continuously present.
- In a healthy individual, microbiota are harmless and can be beneficial.
- They are also known as commensals or microflora.
- The human body contains roughly 100 trillion microbes.
- There are approximately 2.5 kg of microbes in the human body, mostly in the colon.
- There are about 5000 different species of microbes in the gut alone.
- The gut microbiota weighs about 2 kg.
Learning Objectives
- Students should be able to define and explain the functions of normal microbiota.
- Define permanent and temporary microbiota.
- Explain the importance of permanent microbiota.
- Understand microbiota in differing parts of the body.
- Describe the role of normal microbiota in host defense and disease.
Microbiota in the Gut
- The gut microbiota primarily includes bacteria, viruses, fungi, and parasites.
The Human Microbiome
- 25 known phyla (~2000 genera ~5000 species)
- 80% mappability of metagenomes
- 316 million genes
- ~20% sequences not matching microbial genomes
- Functional unknowns (~40% genes without a match in functional databases)
Stuff about Microbiota
- A fetus is sterile at birth, then acquires normal microbiota from its mother, air, and environment.
- Internal organs (spleen, liver, pancreas, bladder, CSF, blood) are generally sterile unless during infections.
- Microbiota vary between individuals based on age, sex, hormonal status, hygiene, diet, and geography.
- A reduction in resident microbiota allows opportunistic microbes to cause infection.
- Human body microbiota is part of natural resistance and forms at birth.
Why Should We Know About Microbiota?
- Understand possible infections resulting from injury.
- Learn about the source and significance of microorganisms from infection sites.
Transient Microbiota
- Microbes temporarily living on or within the human body.
- Attract to moist, warm areas in the external environment.
- These microbes may be washed away by bathing, unable to compete with resident flora, killed by resident flora substances or unable to survive the pH levels of the site.
- They may be flushed away by bodily secretions (tears, sweat, urine, feces).
Where Can We Find Microbiota?
- Skin, Eyes and Ears,Respiratory Tract, Oral Cavity (Mouth), Gastrointestinal Tract, Urogenital Tract.
Skin Microbiota
- Skin acquires transient bacteria from the environment.
- Transients can be washed off, die due to dry conditions, acidic pH, and sweat/oil production.
- Resident bacteria are found in any skin layer, including hair follicles, sweat and sebaceous glands.
- Aerobic bacteria are present in the outer layer (e.g., Staphylococcus epidermidis, Staphylococcus aureus).
- Anaerobic bacteria are present in deeper layers (e.g., Cutibacterium acnes).
- The presence of skin microbiota is generally harmless but may lead to bloodstream infections.
Eyes Microbiota
- Conjunctiva of the eye primarily contains S. epidermidis, followed by S. aureus, C. diphtheroids, and S. pneumoniae.
- Some skin normal flora exist present at fewer amounts, and tears, mucus, and oil protect the conjunctiva from colonization by more bacteria.
Ears Microbiota
- Middle and inner ear is usually sterile.
- Outer ear and auditory canal contains the same skin flora.
- Microbes can enter middle ear from coughs, sneezes, and nose blowing, causing infections.
Respiratory Tract Microbiota
- The upper respiratory tract (nasal cavity, pharynx, larynx, trachea) has many microorganisms.
- Some are normal flora; some are opportunistic, and others (e.g. C. diphtheroids) are carried.
- The lower respiratory tract is usually sterile, due to mucus membranes that remove microbes.
Oral Cavity (Mouth) Microbiota
- Contains both aerobic and anaerobic bacteria.
- Common types include C. diphtheroides, S. aureus, S. epidermidis.
- Yeasts, molds, protozoa, and viruses can also be present.
- Poor hygiene promotes bacterial growth causing dental caries, gingivitis.
- Dental surgery can create a risk of bloodstream infection (endocarditis).
Gastrointestinal Tract Microbiota
- Stomach has few bacteria due to acidity and gastric enzymes.
- Small intestine has few normal flora in the upper part, due to bile killing the bacteria, while the lower part has more.
- Colon is full of bacteria, mostly anaerobic.
- Many fungi, protozoa, and viruses can also be present.
- Some normal flora can cause urinary infections if they travel to other areas (e.g., E. coli).
Urogenital Tract Microbiota
- Kidneys, ureters, and urinary bladder are sterile.
- Lower urethra and external openings have bacteria, yeast, and viruses, similar to skin flora.
- Genital areas are mostly sterile, with the exception of the vagina.
- Lactobacillus spp. maintains an acidic pH to prevent opportunistic infections (fungal vaginitis: Candida albicans, or bacterial vaginosis: Bacteroides spp., Gardnerella vaginalis).
Normal Flora in the Vagina
- Includes various types of bacteria, such as Actinomyces, Staphylococcus, Streptococcus, Corynebacterium, Klebsiella, Proteus, Pseudomonas, Bacteroides, Lactobacillus, Mycoplasma.
- The yeast-like fungus Candida albicans is a common overgrowth.
Sterile Body Zones
- Middle ear, lungs, pleura, paranasal sinuses, blood, endocardium, fallopian tubes, cerebrospinal fluid, meninges, liver, gallbladder, bones/joints, kidneys, ureters, bladder, prostate, epididymis.
Beneficial Functions of Normal Flora
- Protect organs from invading pathogens.
- Stimulate immune system development in newborns.
- Provide nutrients (e.g., vitamin K) aiding digestion and absorption.
Importance of Microbiome
- Microorganisms play a role in many processes including weight control, inflammatory bowel disease, general immune response, and infectious disease resistance.
Harmful Effects of Normal Flora
- Displaced normal flora can become pathogenic, causing infections in other parts of the body (e.g., bloodstream infections, antibiotic-therapy-related infections, cancer).
- Food substances can be converted by normal microbiota into carcinogens.
- Immunocompromised individuals may experience overgrowth of normal flora, causing infections.
Colonization Resistance
- Normal microbiota protects against the overgrowth of harmful microbes.
- Preventing Clostridioides difficile overgrowth during antibiotic therapy.
- Fecal transplants from healthy individuals can cure intractable colitis.
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Description
This quiz explores the essential role of microbiota within the human body, focusing on their functions and significance in health. Students will learn about the different types of microbiota, their locations, and their impact on host defense and disease. Test your understanding of this fascinating aspect of human biology!
