Human Microbiota Overview
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Human Microbiota Overview

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Questions and Answers

What term is used to denote the total number of microorganisms found in a specific area?

  • Microflora
  • Microbiota (correct)
  • Microbiome
  • Metagenomics

    • Which term describes the genomes associated with the microbiota?

  • Microflora
  • Microbiome (correct)
  • Microbiota
  • Ecological niche

    • How many genes does the intestinal microbiota contain compared to the human genome?

  • 22,000 genes
  • 1.5 million genes
  • 3.3 million genes (correct)
  • Over 350 species

    • What classification of microbiota remains fixed in a specific area throughout an individual's life?

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

    What determines the formation of ecological niches in the human body?

    <p>Bacterial adherence and environmental factors</p> Signup and view all the answers

    What percentage of genetic similarity exists among humans?

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

    Which microorganism is commonly found in the gut of most healthy individuals?

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

    How many bacterial species are reported to inhabit the large intestine?

    <p>350 species</p> Signup and view all the answers

    What factor does not affect bacterial adherence in the human microbiome?

    <p>Microbial diversity</p> Signup and view all the answers

    What is the primary factor that most directly contributes to the appearance of microbiota in newborns?

    <p>Mode of delivery</p> Signup and view all the answers

    Which of the following bacteria is NOT typically one of the first colonizers of the newborn oral microbiome?

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

    How do maternal factors influence the newborn microbiota?

    <p>They can alter the concentration and composition of microbiota.</p> Signup and view all the answers

    Which of the following factors is classified as a postnatal factor that can influence microbiota development?

    <p>Diet after the first year of age</p> Signup and view all the answers

    What is a potential consequence of a disturbance in the skin microbiome?

    <p>Development of ectopic dermatitis</p> Signup and view all the answers

    What characteristic defines nonhemolytic bacteria such as viridian streptococci?

    <p>They do not cause hemolysis on blood agar.</p> Signup and view all the answers

    What role do bifidobacterium spp. primarily play in the microbiota of breast-fed infants?

    <p>Production of acid from carbohydrates</p> Signup and view all the answers

    Which of the following best describes the carrier state of microorganisms?

    <p>Is a condition where there are no clinical signs or symptoms</p> Signup and view all the answers

    What is a significant difference between the microbiota of breast-fed and bottle-fed infants?

    <p>Breast-fed infants typically have more prominent lactobacilli.</p> Signup and view all the answers

    What is the role of the microbe pellicle in the development of dental caries?

    <p>It provides a surface for bacterial attachment and multiplication.</p> Signup and view all the answers

    How does Lactobacillus contribute to dental caries?

    <p>It produces lactic acid, lowering the pH and promoting demineralization.</p> Signup and view all the answers

    What is the primary cause of dental caries according to the microbial mechanism described?

    <p>The accumulation of acids from bacterial fermentation of carbohydrates.</p> Signup and view all the answers

    What happens to the pH level in the oral cavity as caries progresses?

    <p>The pH decreases, creating conditions favorable for caries development.</p> Signup and view all the answers

    Which of the following bacteria is characteristic of oral cavity microbiota involved in dental caries?

    <p>Bacteriodes orale</p> Signup and view all the answers

    What phase in the caries process is characterized by acid production from carbohydrate metabolism by bacteria?

    <p>Initial demineralization of enamel.</p> Signup and view all the answers

    What is the role of lysozyme in the skin's defense mechanism?

    <p>It cleaves bonds in peptidoglycan to disrupt bacterial cell walls.</p> Signup and view all the answers

    Which of the following statements about skin microbiota is accurate?

    <p>Malassezia is present in high concentrations in skin niches.</p> Signup and view all the answers

    Which factor contributes to the recolonization of microflora on the skin?

    <p>Hormonal changes during puberty.</p> Signup and view all the answers

    What characterizes the human virome?

    <p>It includes a diverse range of viruses found in human organs.</p> Signup and view all the answers

    What microbe is most commonly found in the oropharynx?

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

    How does lactic acid contribute to skin defense?

    <p>By lowering the skin pH.</p> Signup and view all the answers

    Which statement accurately reflects the amount of microbes in the nasopharynx?

    <p>It features microbial concentrations of around $10^5$ ml.</p> Signup and view all the answers

    What is a potential health implication of the human virome?

    <p>It potentially influences both health and disease states.</p> Signup and view all the answers

    Which type of sweat gland becomes more active following puberty?

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

    What is the primary role of resident microbiota on the skin?

    <p>To inhibit pathogen colonization.</p> Signup and view all the answers

    What percentage of chronic carriers are associated with Streptococcus pneumoniae?

    <p>40-70%</p> Signup and view all the answers

    Which of the following microorganisms is classified as a strict pathogen?

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

    What is a significant risk factor for opportunistic infections?

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

    Which of the following is NOT a characteristic of opportunistic pathogens?

    <p>Always associated with disease</p> Signup and view all the answers

    What factor is likely to decrease the constant microbiota of the skin by 90%?

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

    How many microbes typically exist per cm² on the skin?

    <p>10³-10⁴</p> Signup and view all the answers

    Which of the following microbes is a common component of skin resident microbiota?

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

    What is NOT a method through which an individual can become infected by a microorganism?

    <p>Microbial die-off</p> Signup and view all the answers

    Which of the following conditions could lead to increased susceptibility to opportunistic infections?

    <p>Chronic diseases like diabetes</p> Signup and view all the answers

    Which of the following is a characteristic of acute carriers?

    <p>Always exhibits symptoms of disease</p> Signup and view all the answers

    Study Notes

    Human Microbiota

    • The human microbiome is the collection of microorganisms that reside on and within human tissues and biofluids.
    • Microflora is an outdated term, stemming from the time when only two kingdoms existed (Animalia and Planta).
    • Microbiota refers to the total number of microorganisms found in a specific area.
    • Microbiome encompasses the genomes of the microbiota.
    • Metagenomics is the direct study of genetic material from microbial communities, allowing examination of multiple microbes simultaneously.

    Key Facts

    • The human intestinal microbiota has 3.3 million genes, while the human genome has approximately 22,000 genes.
    • Despite a 99.9% genetic similarity between humans, the intestinal and skin microbiomes differ greatly (80-90%), highlighting individual variations.
    • E. coli is commonly found in the gut of healthy individuals.
    • Staphylococcus epidermitis colonies reside on the skin.

    Classification of Microbiota

    • Resident microbiota (obligatory): Fixed types of microorganisms found in a specific area at a given age.
    • Transient microbiota (facultative): Non-pathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for limited periods (hours, days, or weeks).

    Ecological Niches

    • Ecological niches are specific areas of the body where certain microbes are typically found.
    • The diversity of microbial species varies according to the body region.
    • An adult body harbors approximately 10^13 bacteria.
    • The large intestine contains approximately 350 species of microbes.
    • Bacterial adherence: Bacteria adhere to surfaces using adhesins to resist environmental influences like saliva, chewing, gastrointestinal juices, and intestinal peristalsis.
    • Environmental conditions: Factors like oxygen levels, humidity, nutrients, temperature, and pH contribute to the formation of ecological niches.
    • Disturbances in the microbial balance of a specific region can be associated with disease development - for example, changes in the oral microbiome can lead to dental caries and shifts in the skin microbiome can promote eczema.

    Microbiota Development

    • The fetus is initially sterile.
    • Colonization begins during delivery:
      • Within 4-12 hours: Nonhemolytic bacteria, such as Viridian streptococci (green streptococci, no hemolytic zone around colonies), Streptococcus mutans, S.mitis, and S.salivarius.
      • Within 24-48 hours: Microbiota of the intestinal tract, including Lactobacillus, Bifidobacterium spp., and coliform bacteria
    • Breastfeeding promotes an acidic environment (pH 5) due to carbohydrate-fermenting acid-producing microbes.
    • Bottle-feeding results in a more mixed flora with less prominent Lactobacilli.

    Factors Influencing Microbiota

    • Maternal Factors:
      • Maternal gut microbiota
      • Vaginal infections
      • Periodontitis
    • Postnatal Factors:
      • Antibiotics
      • Breastfeeding
      • Host genetics
      • Environment
      • Diet (particularly after the first year of life)

    Interaction of Microorganisms and the Host

    • Microbes can transiently or permanently colonize a person.
    • Disease occurs when the interaction between a microbe and a human host leads to a pathogenic process that damages the host.

    Causative Agents of Infectious Diseases

    • Strict pathogens: Always associated with disease in humans (e.g. Mycobacterium tuberculosis, Neisseria gonorrhoeae, Francisella tularensis, Plasmodium spp., Rhabdovirus).
    • Opportunistic pathogens: Typically part of the normal microbiota but cause disease when introduced to unprotected sites (e.g. bloodstream, tissues) (e.g. Staphylococcus aureus, E. coli, Candida albicans).

    Skin Microbiota

    • Transient microbiota: Found on the skin's surface.
    • Resident microbiota: Constant in deeper skin layers.
    • Approximately 10^3-10^4 microbes per cm2.
    • Common residents include:
      • Staphylococcus epidermidis (90%)
      • Corynebacterium
      • Cutibacterium acnes
      • Malassezia
      • Candida

    Factors Influencing Skin Microbiota

    • Detergents: Decrease transient and surface-level resident microbiota by up to 90% but recolonization occurs within 8 hours.
    • Disinfectants: Can kill resident microbiota.
    • Sex, age, climate, UV rays, hygiene, profession, and disease all play a role in shaping the skin microbiota.

    Skin as a Defense Barrier

    • Intact skin serves as the first line of defense against microbial invasion.
    • Skin's dryness inhibits microbial growth.
    • Sweat glands (eccrine and apocrine) secrete sweat and nutrients, contributing to microbial populations.
      • Lysozyme in sweat breaks down peptidoglycan, a component of bacterial cell walls.
      • Lactic acid in sweat lowers pH, suppressing many microbes.
    • Sebaceous glands, attached to hair follicles, secrete sebum, providing a nutrient source for microbes.

    Skin Mycobiome

    • The skin mycobiome refers to the normal fungal species present on the skin.
    • Fungi account for 30% of the skin microbiota, with Malassezia strains dominating.
    • While Malassezia is often associated with healthy skin, it has also been linked to conditions like dandruff and eczema.

    Human Virome

    • The human virome encompasses all the viruses found in or on human organs.
    • Human feces contain approximately 10^9 virus-like particles (VLPs) per gram.
    • Bacteriophages represent a significant proportion (96.1%) of gut viral populations.
    • The human virome potentially influences human health.

    Microbiota of the Nasopharynx and Oropharynx

    • Nasopharynx: 10^5 microbes/ml
      • Staphylococcus epidermidis
      • Corynebacterium
      • Propionibacterium
      • Haemophilus parainfluenzae
      • Pathogens: Staphylococcus aureus, Staphylococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis
    • Oropharynx: 10^7 microbes/ml
      • Staphylococcus
      • Streptococcus
      • Corynebacterium
      • Propionibacterium
      • Neisseria spp.
      • Branhamella catarrhalis
      • Bacteroides
      • Fusobacterium (anaerobes)
      • Enterococcus
      • Pathogens: Streptococcus (α-hemolytic), Corynebacterium diphtheriae, Klebsiella pneumoniae, Pseudomonas aeruginosa

    Microbiota of the Oral Cavity

    • Saliva: 10^8 microbes/ml
    • Dental plaque: 10^11 microbes/gram
      • Streptococcus: S.salivarius, S.sanguis, S.milleri, S.mutans
      • Staphylococcus, Enterococcus, Veilonella, Neisseria, Bacteroides orale, Fusobacterium nucleatum, Leptrotrichia buccalis, Actinomyces, Vibrio, Spirocheta (Treponema orale, Borrelia buccalis, Leptospira dentium), Candida albicans (Saccharomyces), Prevotella malinogenica, Porphyromonas gingivalis.

    Dental Caries

    • Multifactorial disease involving disintegration of tooth surfaces.
    • Enamel demineralization is caused by acids produced during bacterial fermentation.
    • Dentin and cement are subsequently decomposed.

    Microbial Mechanism of Caries

    1. Following meals, a thin saliva layer called a microbial pellicle forms on tooth surfaces.
    2. Bacteria attach to this pellicle.
    3. Over time, bacteria multiply and break down carbohydrates, producing glucans and fructans.
    4. This process leads to a decrease in pH and anaerobic conditions favorable for facultative and anaerobic bacteria.
    5. Lactobacillus further acidifies the environment by producing lactic acid.
    6. High concentrations of lactic acid cause enamel demineralization and initiate dental caries.

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    Description

    This quiz explores the human microbiome, its classification, and key facts about microorganisms that inhabit the body. Learn about the concepts of microbiota, microbiome, and metagenomics, along with the differences between various microbial populations in humans.

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