Human Microbiome Overview
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Questions and Answers

What distinguishes the term 'microbiota' from 'microbiome'?

  • Microbiota includes viruses present in an area.
  • Microbiota refers to the total number of microorganisms in an area. (correct)
  • Microbiota refers to the genetic material of bacteria.
  • Microbiota only includes beneficial bacteria.

    • What is the primary distinction between resident and transient microbiota?

  • Resident microbiota are pathogenic while transient are not.
  • Transient microbiota are always beneficial to the host.
  • Transient microbiota are permanent residents of an area.
  • Resident microbiota are fixed types found consistently, while transient microbiota are temporary. (correct)

    • How many species of microbes are typically found in the large intestine of an adult body?

  • 99.9%
  • 350 (correct)
  • 1013
  • 3.3 million

    • Which component is most critical for the formation of ecological niches within the human body?

    <p>Bacterial adherence mediated by adhesins</p> Signup and view all the answers

    What percentage of genetic similarity is found among humans?

    <p>99.9%</p> Signup and view all the answers

    Which of the following statements about the intestinal microbiota is true?

    <p>It is composed of 3.3 million genes.</p> Signup and view all the answers

    What is the common misconception about the term 'microflora'?

    <p>It was outdated when the two-kingdom classification was developed.</p> Signup and view all the answers

    Which statement is correct regarding the uniqueness of an individual's microbiome?

    <p>It has an 80-90% difference between skin and intestinal microbiome.</p> Signup and view all the answers

    Which of the following microorganisms is typically found in the gut of healthy subjects?

    <p>E. coli</p> Signup and view all the answers

    What is the main cause of enamel demineralization in dental caries?

    <p>Acid products of bacterial fermentation</p> Signup and view all the answers

    What is the main function of the lysozyme secreted by sweat glands?

    <p>Cleaves the bond between NAG and NAM in peptidoglycan</p> Signup and view all the answers

    Which microorganisms contribute to the formation of the microbe pellicle on teeth?

    <p>Streptococcus and Staphylococcus</p> Signup and view all the answers

    Which component of the skin microbiome represents the majority of fungal species?

    <p>Malassezia</p> Signup and view all the answers

    Which of the following pathogens is NOT typically associated with oral microbiota?

    <p>Corynebacterium diphtheriae</p> Signup and view all the answers

    How does the pH level influenced by lactic acid secreted from sweat glands affect microbial colonization?

    <p>Suppresses microbial colonization</p> Signup and view all the answers

    What role do Lactobacillus species play in the development of dental caries?

    <p>They contribute to lactic acid production</p> Signup and view all the answers

    What is one of the ways that resident microbiota can be reduced according to the content?

    <p>Exposure to UV rays</p> Signup and view all the answers

    How does the microbe pellicle contribute to the pathogenicity of dental caries?

    <p>It serves as a niche for bacterial colonization</p> Signup and view all the answers

    What is the relationship between carbohydrate cleavage and the acidic environment created by oral bacteria?

    <p>Carbohydrate cleavage leads to acid production</p> Signup and view all the answers

    What characteristic best describes the skin's initial defense against microbial invasion?

    <p>It is dry and not suited for microbial growth</p> Signup and view all the answers

    What role do sebaceous glands play in the skin's microbiome?

    <p>They provide nutrients through the secretion of sebum</p> Signup and view all the answers

    Which of the following best describes dental caries?

    <p>A polyetiological disease involving multiple factors</p> Signup and view all the answers

    What is the effect of the anaerobic conditions promoted by extensive bacterial metabolism?

    <p>Promotion of harmful anaerobic bacteria</p> Signup and view all the answers

    Which of the following statements about the human virome is true?

    <p>It influences human health and potentially disease</p> Signup and view all the answers

    Which group of bacteria is typically found at higher concentrations in dental plaque compared to saliva?

    <p>Streptococcus species</p> Signup and view all the answers

    What is the typical microbe concentration observed in the oropharynx?

    <p>107/ml</p> Signup and view all the answers

    Which of the following is NOT associated with the Malassezia genus?

    <p>Bacterial infections</p> Signup and view all the answers

    What is the typical concentration of microbes in saliva?

    <p>10^8/ml</p> Signup and view all the answers

    Which type of gland is primarily active after puberty and secretes sweat along with nutrients?

    <p>Apocrine glands</p> Signup and view all the answers

    What defines an acute carrier of infectious pathogens?

    <p>A carrier that transiently carries pathogens without symptoms</p> Signup and view all the answers

    Which pathogen is classified as a strict pathogen?

    <p>Mycobacterium tuberculosis</p> Signup and view all the answers

    Which of the following is NOT a risk factor for opportunistic infections?

    <p>Regular exercise</p> Signup and view all the answers

    What differentiates opportunistic pathogens from strict pathogens?

    <p>Strict pathogens are always associated with disease in humans.</p> Signup and view all the answers

    Which skin microbiota is considered to be constant and found in deeper parts of the skin?

    <p>Resident microbiota</p> Signup and view all the answers

    What percentage of skin microbiota is typically composed of Staphylococcus epidermidis?

    <p>90%</p> Signup and view all the answers

    What effect do detergents have on skin microbiota?

    <p>Decreases superficial constant microbiota by 90%</p> Signup and view all the answers

    Which of the following is a common opportunistic pathogen?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    Which group of microorganisms are classified as chronic carriers infecting a significant number of people?

    <p>Chronic carriers of Staphylococcus aureus and Streptococcus pneumoniae</p> Signup and view all the answers

    What is a characteristic of microbes that permanently colonize a human host?

    <p>They do not necessarily cause disease.</p> Signup and view all the answers

    What role does gut microbiota play in neuropsychiatric disorders?

    <p>They play a critical role in the pathogenesis of these disorders.</p> Signup and view all the answers

    Which of the following bacteria are found in the colon's microbiota?

    <p>Fusobacterium and Eubacterium</p> Signup and view all the answers

    What is the pH level in the jejunum and ileum of the small intestine?

    <p>pH 6-7</p> Signup and view all the answers

    What is the potential impact of antibiotic courses on patients with gastrointestinal diseases regarding mental health?

    <p>They can increase the burden of depression and anxiety.</p> Signup and view all the answers

    Which of the following is NOT identified as a neuroactive compound produced by gut microbes?

    <p>Insulin</p> Signup and view all the answers

    Which bacteria are commonly found in the urogenital microbiota of the urethra?

    <p>Staphylococcus epidermidis and Peptostreptococcus</p> Signup and view all the answers

    Study Notes

    Human Microbiome Terminology

    • Microflora is an outdated term used when only two kingdoms (Animalia and Planta) were recognized.
    • Microbiota refers to the total number of microorganisms found in a specific area.
    • Microbiome encompasses the genomes of the microbiota, studied through genome examination.
    • Metagenomics is the direct study of genetic material from microbial communities, analyzing DNA from multiple bacteria simultaneously.

    Human Microbiome Facts

    • The intestinal microbiota harbors 3.3 million genes, vastly exceeding the approximately 22,000 genes in the human genome.
    • Humans share 99.9% genetic similarity, but their intestinal and skin microbiomes differ by 80-90%, highlighting the unique individuality of individual microbiomes.
    • The human microbiome exhibits regional diversity, with E. coli prevalent in the gut of most healthy individuals and Staphylococcus epidermitis inhabiting the skin.

    Microbiota Classification

    • Resident or constant (obligatory) microbiota: Fixed types of microorganisms permanently residing in a given area at a specific age.
    • Transient microbiota (facultative): Non-pathogenic or potentially pathogenic microorganisms temporarily inhabiting the skin or mucous membranes for hours, days, or weeks.

    Ecological Niches

    • Each body region with a characteristic set of microbes constitutes an ecological niche.
    • The types of microorganisms vary across different areas of the body.
    • The human body harbors an estimated 10^13 bacteria, with 350 species in the large intestine.
    • Bacterial adherence (via adhesins) and exposure to microorganisms influence the formation of ecological niches.
    • Individuals can be categorized as carriers, carrying microorganisms that may or may not cause disease, and classified into two groups:
      • Acute carrier: Exhibiting a short-term carrier state.
      • Chronic carrier: Carrying specific microbes for prolonged periods, for example, individuals carrying Staphylococcus aureus (20-40%), Streptococcus pneumoniae (40-70%), or Salmonella typhi (a lower percentage).
    • Exposure to a microorganism can result in:
      • Transient colonization: The microbe temporarily resides in the individual.
      • Permanent colonization: The microbe becomes a permanent resident.
      • Disease: The interaction between the microbe and the human host leads to a pathogenic process, causing damage to the host.

    Causative Agents of Infectious Diseases

    • Strict pathogens: Microorganisms consistently associated with disease in humans, such as Mycobacterium tuberculosis, Neisseria gonorrhoeae, Francisella tularensis, Plasmodium species, and Rhabdoviruses.
    • Opportunistic pathogens: Typically harmless members of the normal microbiota that can cause disease when introduced into vulnerable sites (e.g., bloodstream, tissues), examples include Staphylococcus aureus, Escherichia coli, and Candida albicans.

    Risk Factors for Opportunistic Infections

    • Immunodeficiency
    • Chronic diseases (e.g., diabetes)
    • Gastric ulcers
    • Stress
    • Antibacterial treatment
    • Malnutrition
    • Avitaminosis

    Skin Microbiota

    • Transient microbiota: Superficial, temporary residents.
    • Resident microbiota: Constant inhabitants of deeper skin layers.
    • Approximately 10^3-10^4 microbes reside per square centimeter.
    • Common skin microbiota members include:
      • Staphylococcus epidermidis (90%)
      • Corynebacterium
      • Cutibacterium acnes
      • Malassezia
      • Candida

    Factors Influencing Skin Microbiota

    • Detergents: Reduce transitory and superficial microbiota by 90%, with recolonization occurring within 8 hours.
    • Disinfectants: Eliminate resident microbiota.
    • Sex
    • Age
    • Climate
    • UV rays
    • Hygiene
    • Profession
    • Diseases

    Skin as a Defense Barrier

    • Intact skin serves as the first line of defense against microbial invasion.
    • Skin's dryness makes it unsuitable for many microbial growth.
    • Skin microbiota is sustained by nutrients provided by sweat and sebaceous glands.
    • Sweat glands:
      • Eccrine glands: Secrete sweat.
      • Apocrine glands: Secrete sweat and nutrients, more active after puberty.
      • Sweat contains:
        • Lysozyme: Breaks down peptidoglycan, a bacterial cell wall component.
        • Lactic acid: Lowers pH to 3-5, inhibiting bacterial colonization.
    • Sebaceous glands:
      • Attached to hair follicles.
      • Secrete sebum, supporting microbial growth up to 10^6 per square centimeter.

    Skin Mycobiome

    • The skin mycobiome refers to the fungal species inhabiting the skin.
    • Fungi constitute 30% of the skin microbiota, with Malassezia strains dominating.
    • Malassezia species, including M. globosa, M. restricta, and M. furfur, represent over 90% of fungal populations in most skin niches.
    • The role of Malassezia on the skin is controversial, linked to both healthy skin and conditions like dandruff and eczema.

    Human Virome

    • The human virome encompasses all viruses residing within or on human organs, including the skin.
    • Human stools contain at least 10^9 virus-like particles (VLPs) per gram.
    • Bacteriophages comprise 96.1% of the human gut viral populations.
    • The human virome potentially influences human health, beyond disease.

    Microbiota of Nasopharynx and Oropharynx

    • Nasopharynx:
      • Microbe amount: 10^5 per milliliter.
      • Microbes: Staphylococcus epidermidis, Corynebacterium, Propionibacterium, Haemophilus parainfluenzae.
      • Pathogens: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis.
    • Oropharynx:
      • Microbe amount: 10^7 per milliliter.
      • Microbes: Staphylococcus, Streptococcus, *Corynebacterium, Propionibacterium, Neisseria species, Branhamella catarrhalis, Bacteroides, Fusobacterium, Enterococcus.
      • Pathogens: Streptococcus (α-hemolytic), Corynebacterium diphtheriae, Klebsiella pneumoniae, Pseudomonas aeruginosa.

    Microbiota of Oral Cavity

    • Microbe amount in saliva: 10^8 per milliliter.
    • Microbe amount in teeth plaque: 10^11 per gram.
    • Microbes: Streptococcus salivarius, S. sanguis, S. milleri, S. mutans, Staphylococcus, Enterococcus, Veilonella, Neisseria, Bacteroides orale, Fusobacterim nucleatum, Leptrotrichia buccalis, Actinomyces, Vibrio, Spirocheta (including Treponema orale, Borrelia buccalis, Leptospira dentium), Candida albicans, Saccharomyces, Prevotella malinogenica, Porphyromonas gingivalis, etc.

    Dental Caries

    • Polyaethiologic disease, meaning multiple factors contribute to its development.
    • Caries refers to tooth disintegration, starting at the surface and progressing inward.
    • Demineralization of the enamel surface is caused by acidic byproducts of bacterial fermentation.
    • Subsequent decomposition of the dentin and cement follows.

    Microbial Mechanism of Caries

    1. After a meal, a thin layer of saliva (microbe pellicle, around 0.1 micrometer) forms on the tooth surface.
    2. The microbe pellicle provides a site for bacteria to attach.
    3. Over time, microbes multiply and ferment carbohydrates, producing glucan and fructan, lowering pH and promoting anaerobic conditions.
    4. The resulting environment favors facultative anaerobes and even anaerobes.
    5. Lactobacillus bacteria, producing lactic acid, further acidify the environment.
    6. The high concentration of lactic acid leads to demineralization, initiating dental caries.
    7. Dental caries is also a biofilm, shielding bacteria from immune cells and antibiotics.

    Gastrointestinal Microbiota

    • Stomach:
      • pH: 1-3.
      • Microbe amount: 10^1-10^3 colony-forming units per milliliter (CFU/ml).
      • Oxygen partial pressure (PO2): 77 mmHg.
      • Microbes: Lactobacillus, Streptococcus, Staphylococcus, Enterobacteriaceae.
    • Duodenum:
      • Microbe amount: 10^1-10^3 CFU/ml.
      • PO2: 33 mmHg.
      • Microbes: Lactobacillus, Streptococcus, Staphylococcus, Enterobacteriaceae.
    • Small Intestine (jejunum and ileum):
      • pH: 6-7.
      • Microbe amount: 10^4-10^7 CFU/ml.
      • PO2: 33 mmHg.
      • Microbes: Bifidobacterium, Bacteroides, Lactobacillus, Streptococcus, Enterobacteriaceae.
    • Colon:
      • pH: 7.
      • Microbe amount: 10^10-10^11 CFU/ml.
      • PO2: < 33 mmHg.
      • Microbes: Fusobacterium, Eubacterium, Clostridium, Peptostreptococcus, Bifidobacterium, Streptococcus, Bacteroides, Lactobacillus, Enterobacteriaceae.

    Gut-Brain-Microbiota Axis

    • Variations in gut microbiota play a significant role in the development of neuropsychiatric disorders.
    • Communication along this axis is bidirectional.
    • Antibiotic treatment for gastrointestinal diseases can increase the risk of depression and anxiety symptoms.
    • Gut microbes provide neuroactive compounds and immune modulators, including serotonin, dopamine, γ-aminobutyric acid, acetylcholine, histamine, and short-chain fatty acids.

    Urogenital Microbiota

    • Vagina:
      • Microbe amount: 10^9 per milliliter.
      • Microbes: Staphylococcus epidermidis, Peptostreptococcus, Neisseria species, Corynebacterium species.
    • Urethra:
      • Microbes: Staphylococcus epidermidis, Streptococcus, Corynebacterium species.

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    Description

    Explore the key terms and fascinating facts related to the human microbiome. Learn about microbiota, microbiome, and the significance of metagenomics in understanding our microbial communities. This quiz covers essential concepts that highlight the diversity and individuality of human microbiomes.

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