Microbes: Useful Roles Quiz
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Questions and Answers

Who is often credited as the first person to observe microorganisms using a microscope?

  • Semmelweis
  • van Leeuwenhoek (correct)
  • Akshamsaddin
  • Louis Pasteur

    • Which individual's work paved the way for later scientists to explore the microbial world?

  • Akshamsaddin
  • Louis Pasteur
  • van Leeuwenhoek (correct)
  • Semmelweis

    • Who was a pioneer of antiseptic procedures and worked as an obstetrician in Vienna?

  • Semmelweis (correct)
  • Akshamsaddin
  • van Leeuwenhoek
  • Louis Pasteur

    • Who claimed that diseases, like plants and animals, have 'invisible seeds'?

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

    Who pioneered antiseptic surgery with the use of carbolic acid?

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

    Who observed higher patient mortality in doctor-run clinics than midwife-run clinics?

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

    Who developed postulates to establish a causal relationship between microbes and disease?

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

    Who disproved spontaneous generation and developed techniques for vaccine production?

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

    Which scientist demonstrated that microbes can cause disease by isolating a fungus that killed silkworms?

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

    What is the resolution limit of light microscopy due to visible light's physical constraints?

    <p>0.2 nanometers</p> Signup and view all the answers

    Which microscopy technique observes cell structure details by directing electrons through or scattering them within the specimen?

    <p>Transmission EM</p> Signup and view all the answers

    What distinguishes gram-positive and gram-negative bacteria through crystal violet, iodine, alcohol, and safranin?

    <p>The Gram stain</p> Signup and view all the answers

    Which staining technique detects mycobacteria with high mycolic acid concentrations and uses carbol fuchsin and harsh washes?

    <p>The acid-fast stain</p> Signup and view all the answers

    What type of staining involves using a single dye?

    <p>Simple staining</p> Signup and view all the answers

    Which microscopy technique uses fluorophores to excite and detect light at different wavelengths, providing powerful cellular component visualization?

    <p>Fluorescence microscopy</p> Signup and view all the answers

    What is the basis for evidence of the two-domain system in microbiology?

    <p>Genetic information, particularly ribosomal RNA sequences</p> Signup and view all the answers

    Which technique is used to improve contrast in microscopy?

    <p>Dark-field microscopy</p> Signup and view all the answers

    What is the calculation for total magnification in a light microscope?

    <p>$\text{Total magnification} = \text{Ocular lens power} \times \text{Objective lens power}$</p> Signup and view all the answers

    What is the purpose of using oil with the 100X lens in a light microscope?

    <p>To improve resolution and minimize refraction</p> Signup and view all the answers

    Which type of microscopy involves illuminating the sample with light that does not pass directly through the objective lens?

    <p>Dark-field microscopy</p> Signup and view all the answers

    What distinguishes Bacteria from Archaea according to the text?

    <p>Genetic differences and cell wall composition</p> Signup and view all the answers

    Which technique is used to detect unique proteins in microbes?

    <p>Fluorescent compound tagging via antibodies</p> Signup and view all the answers

    What are the two classified shapes of bacterial cells mentioned in the text?

    <p>Cocci and bacilli</p> Signup and view all the answers

    What is the most conserved component of LPS (lipopolysaccharide)?

    <p>Lipid A</p> Signup and view all the answers

    Which type of bacteria have an outer membrane with porins allowing passage of AAs and simple sugars?

    <p>Gram-negative bacteria</p> Signup and view all the answers

    What is the basic structure of LPS (lipopolysaccharide)?

    <p>Lipid A, core polysaccharide, and O antigen</p> Signup and view all the answers

    What are the groupings of prokaryotes after binary fission according to the text?

    <p>Diplococcus, long chains, cubical packets, and grapelike clusters</p> Signup and view all the answers

    What are the different transport systems for molecules across the bacterial cell membrane mentioned in the text?

    <p>Facilitated diffusion, active transport, and protein secretion</p> Signup and view all the answers

    What is the structure of peptidoglycan mentioned in the text?

    <p>Peptidoglycan consists of glycan chains cross-linked by short peptides</p> Signup and view all the answers

    Who coined the term 'virus' to describe a filterable infectious agent?

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

    What is the physical structure of a virion?

    <p>Nucleic acid + protein coat (capsid)</p> Signup and view all the answers

    What is the smallest virus known?

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

    How was smallpox eradicated?

    <p>Through a global vaccination campaign</p> Signup and view all the answers

    Which of the following is true about latent infections?

    <p>They have periods of inactivity followed by reactivation</p> Signup and view all the answers

    Where do DNA viruses often replicate?

    <p>Host cell nucleus</p> Signup and view all the answers

    What is the function of a virion?

    <p>A complete, infectious viral particle outside a host cell</p> Signup and view all the answers

    Which type of microscopy observes cell structure details by directing electrons through or scattering them within the specimen?

    <p>Transmission electron microscopy</p> Signup and view all the answers

    What distinguishes acute infections from persistent infections?

    <p>Acute infections are short-lived with rapid onset, while persistent infections last an extended period</p> Signup and view all the answers

    What is the role of cytopathic effect (CPE) in viral infection?

    <p>It refers to visible damage to host cells caused by viral infection</p> Signup and view all the answers

    What is the classification criterion for enveloped viruses?

    <p>The presence of lipid envelopes</p> Signup and view all the answers

    What can some viruses contribute to by integrating their genetic material into the host cell's DNA?

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

    What distinguishes eukaryotic cells from prokaryotic cells?

    <p>Eukaryotic cells have a true nucleus and membrane-bound organelles, while prokaryotic cells lack a true nucleus and membrane-bound organelles.</p> Signup and view all the answers

    What method inhibits microbial growth and extends shelf life?

    <p>Low-temperature storage</p> Signup and view all the answers

    What is a strain in microbiology?

    <p>A group of microorganisms derived from a single original isolate</p> Signup and view all the answers

    How are prokaryotes identified?

    <p>Through microscopic morphology, culture characteristics, and metabolic capabilities</p> Signup and view all the answers

    What aids in prokaryote identification?

    <p>Metabolic capabilities</p> Signup and view all the answers

    What methods are used to classify species and strains?

    <p>$16S rRNA$ sequencing, serological typing, and $MLST$</p> Signup and view all the answers

    What is the purpose of chemical preservatives in microbial preservation?

    <p>To inhibit microbial growth and extend shelf life</p> Signup and view all the answers

    What is the key characteristic of biofilms?

    <p>They are resistant to antibiotics and immune responses</p> Signup and view all the answers

    How can prokaryotes be classified?

    <p>Morphology, immunological methods, and molecular techniques</p> Signup and view all the answers

    What aids in distinguishing different strains of microorganisms?

    <p>Metabolic capabilities</p> Signup and view all the answers

    Which microorganism is responsible for causing a fatal brain infection and is found in warm freshwater?

    <p>Naegleria fowleri</p> Signup and view all the answers

    What type of bacteria can grow with or without oxygen?

    <p>Facultative anaerobes</p> Signup and view all the answers

    Which enzyme breaks down hydrogen peroxide?

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

    What is the intermediate host for Schistosoma mansoni, a blood fluke causing schistosomiasis?

    <p>Freshwater snail</p> Signup and view all the answers

    Which organism causes gastrointestinal illness through waterborne transmission?

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

    What type of bacteria have different temperature and pH preferences?

    <p>Psychrophile, psychrotroph, mesophile, thermophile, hyperthermophile, neutrophile, acidophile, alkalophile, halophile, and halotolerant bacteria</p> Signup and view all the answers

    Which organism causes candidiasis and is multidrug-resistant?

    <p>Candida auris</p> Signup and view all the answers

    What causes ascariasis and is transmitted through contaminated food/water?

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

    What is the enzyme that converts superoxide radicals into hydrogen peroxide and oxygen?

    <p>Superoxide dismutase</p> Signup and view all the answers

    What organism causes toxoplasmosis and is transmitted by contaminated food or cat feces?

    <p>Toxoplasma gondii</p> Signup and view all the answers

    Which type of bacteria cannot survive in the presence of oxygen?

    <p>Obligate anaerobes</p> Signup and view all the answers

    What is the difference between prevalence and incidence?

    <p>Prevalence measures the total number of cases at any time in a given population, while incidence measures the number of new cases occurring over a specific period in a given population.</p> Signup and view all the answers

    What is the case-fatality rate?

    <p>The percentage of the population that dies from a specific disease.</p> Signup and view all the answers

    What distinguishes common/single-source epidemics from propagated epidemics?

    <p>Common/single-source epidemics involve rapid rise in cases from exposure to a single source of the pathogen, while propagated epidemics show slow rise in cases suggesting contagious disease spreading in the population.</p> Signup and view all the answers

    What defines a pandemic?

    <p>A global outbreak affecting an unusually large number of cases over a larger region.</p> Signup and view all the answers

    Which type of vaccine contains killed pathogens?

    <p>Inactivated vaccine</p> Signup and view all the answers

    What does sterilizing immunity prevent?

    <p>Infection completely</p> Signup and view all the answers

    Which term describes the transfer of genetic material between bacterial cells?

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

    What do seropositive individuals have produced specific antibodies to?

    <p>A pathogen</p> Signup and view all the answers

    What do purified antigens (toxoids/subunit vaccines) necessitate the use of?

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

    What does virulence indicate in a microorganism?

    <p>Ability to cause disease</p> Signup and view all the answers

    What is the function of genomic islands?

    <p>Determine virulence of a strain</p> Signup and view all the answers

    What is the function of prophages in bacteria?

    <p>Carry virulence factors</p> Signup and view all the answers

    What allows herd immunity to occur?

    <p>Sufficient portion of the population being immune</p> Signup and view all the answers

    How did Vibrio cholera acquire genes allowing it to cause disease?

    <p>Horizontal gene transfer</p> Signup and view all the answers

    What distinguishes primary pathogens from opportunists?

    <p>Disease-causing ability</p> Signup and view all the answers

    What is the function of pathogenicity islands?

    <p>Contain virulence factors</p> Signup and view all the answers

    Which type of toxins affect the nervous system?

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

    What is the function of B subunits in AB toxins?

    <p>Responsible for binding to host cell receptors</p> Signup and view all the answers

    Which term refers to proteins that activate a large number of T cells?

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

    What causes 'Scalded Child Syndrome'?

    <p>Exfoliative toxins produced by Staphyylococcus aureus</p> Signup and view all the answers

    Which major project aimed to identify major organisms in the human microbiota?

    <p>The Human Microbiome Project</p> Signup and view all the answers

    What are the five major bacterial phyla dominating the gut microbiota?

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

    What is the main function of commensal microbiota?

    <p>Benefit the host</p> Signup and view all the answers

    What is the role of germ-free mice in microbiota studies?

    <p>To study specific effects of introducing particular microbes</p> Signup and view all the answers

    What is dysbiosis associated with?

    <p>Metabolic disorders and inflammatory bowel diseases</p> Signup and view all the answers

    How does colonization resistance protect the host?

    <p>Excluding invading pathogens and inhibiting overgrowth of opportunistic pathogens</p> Signup and view all the answers

    What is the purpose of fecal microbiota transplant (FMT) in gastrointestinal disease treatment?

    <p>Restoring a balanced microbial community</p> Signup and view all the answers

    What is gene richness in a microbial community?

    <p>Number of different genes within a microbial community</p> Signup and view all the answers

    What is anabolism in microbial metabolism?

    <p>Usage of energy to construct molecules like proteins and nucleic acids</p> Signup and view all the answers

    How does exposure to environmental microbes impact immune system development?

    <p>Stimulates immune maturation</p> Signup and view all the answers

    What is the main function of direct colonization resistance?

    <p>Prevent colonization and inhibit growth independently of host interactions</p> Signup and view all the answers

    What did the study by Ridaura et al. demonstrate about gut microbiota?

    <p>Transplanting gut microbiota from obese mice led to an increase in body fat in lean mice.</p> Signup and view all the answers

    What are pathobionts in the context of gut microbiota?

    <p>Residents with potential to induce pathology.</p> Signup and view all the answers

    What is the term for the natural habitat where a pathogen lives?

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

    What type of transmission occurs person to person via air, physical contact, ingestion, or vector?

    <p>Horizontal transmission</p> Signup and view all the answers

    What do prospective, cross-sectional, and retrospective studies aim to do in epidemiology?

    <p>Compare actions following an outbreak</p> Signup and view all the answers

    What type of epidemics stem from exposure to a single source?

    <p>Common-source epidemics</p> Signup and view all the answers

    What is the term for diseases transmitted from animals to humans?

    <p>Zoonotic diseases</p> Signup and view all the answers

    What are the first-line defenses against pathogens?

    <p>Innate immune responses</p> Signup and view all the answers

    Which type of immunity is immediate and non-specific?

    <p>Innate immunity</p> Signup and view all the answers

    Which type of studies determine risk factors in epidemiology?

    <p>Analytical studies</p> Signup and view all the answers

    What influences disease epidemiology in terms of pathogen and host characteristics?

    <p>Host immunity and pathogen virulence</p> Signup and view all the answers

    What is the term for the transfer of genetic material between bacterial cells?

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

    What role do natural, transmission, and terminal hosts play in pathogen life cycles?

    <p>Natural hosts maintain pathogen populations while transmission hosts spread them.</p> Signup and view all the answers

    Which type of microscopy observes cell structure details by directing electrons through or scattering them within the specimen?

    <p>Transmission electron microscopy (TEM)</p> Signup and view all the answers

    Study Notes

    Bacterial Cell Structures and Transport Processes

    • Technique using fluorescent compound tagging via antibodies to detect unique proteins in microbes
    • Bacterial cell shapes classified as cocci (spherical) and bacilli (cylindrical), with examples like E. coli, listeria, and salmonella
    • Groupings of prokaryotes after binary fission, including diplococcus, long chains, cubical packets, and grapelike clusters
    • Different transport systems for molecules across the cell membrane, including facilitated diffusion, active transport, and protein secretion
    • Gram-negative bacteria have an outer membrane with porins allowing passage of AAs and simple sugars, while gram-positive bacteria have a thick peptidoglycan cell wall
    • Peptidoglycan structure consisting of NAG-NAM chains and wall peptides forming glycan chains and tetrapeptide chains
    • Basic structure of LPS (lipopolysaccharide) including Lipid A, core polysaccharide, and O antigen, which can cause symptoms characteristic of bacterial infection and help bacteria evade the immune system
    • Lipid A is the most conserved component of LPS and is recognized by the immune system
    • O antigen helps identify bacterial species or strains and varies in number and type of sugar molecules
    • Core polysaccharide is a unique pattern of sugars between Lipid A and O antigen
    • Bacterial transport processes include diffusion, passive transport, active transport, and facilitated transport
    • Prokaryotes use a variety of secretion systems for active movement of proteins out of the cell, such as extracellular enzymes and external structures

    Microbial Pathogens, Microorganism Characteristics, and Control Methods

    • Candida auris and albicans cause candidiasis, with C. auris being multidrug-resistant.
    • Acanthamoeba keratitis is a protozoan causing eye infection, often linked to contact lens use.
    • Cryptosporidium is a protozoan causing gastrointestinal illness through waterborne transmission.
    • Toxoplasma gondii causes toxoplasmosis, transmitted by contaminated food or cat feces.
    • Various tapeworm species are transmitted through ingesting undercooked meat.
    • Ascaris is a roundworm causing ascariasis, transmitted through contaminated food/water.
    • Naegleria fowleri is an amoeba causing fatal brain infection, found in warm freshwater.
    • Schistosoma mansoni is a blood fluke causing schistosomiasis, with a freshwater snail as an intermediate host.
    • Psychrophile, psychrotroph, mesophile, thermophile, hyperthermophile, neutrophile, acidophile, alkalophile, halophile, and halotolerant bacteria have different temperature and pH preferences.
    • Facultative anaerobes can grow with or without oxygen, while obligate aerobes require oxygen and obligate anaerobes cannot survive in its presence.
    • Catalase is an enzyme that breaks down hydrogen peroxide, and superoxide dismutase converts superoxide radicals into hydrogen peroxide and oxygen.
    • Sterilization eliminates all microbial life, disinfection reduces pathogens on surfaces, pasteurization treats food and beverages, decontamination reduces microbial populations, sanitization lowers microbial levels to meet health standards, and preservation inhibits microbial growth.

    Microbial Toxins and Human Microbiota

    • Exotoxins are proteins released by living bacteria that can harm the host, while endotoxins are lipopolysaccharides present in the outer membrane of Gram-negative bacteria.
    • Neurotoxins affect the nervous system (e.g., Botulinum toxin, Tetanus toxin), enterotoxins affect the intestines (e.g., Cholera toxin, Enterotoxigenic E. coli toxins), and cytotoxins damage or kill host cells (e.g., Diphtheria toxin, Shiga toxin).
    • Effector molecules exert specific effects on cells, including toxins, while exotoxins are produced and released by bacteria into the environment, and endotoxins are part of the bacterial cell wall.
    • AB toxins have B subunits responsible for binding to host cell receptors and A subunits responsible for toxic activity, and they enter host cells through receptor-mediated endocytosis.
    • "Scalded Child Syndrome" is caused by exfoliative toxins produced by Staphyylococcus aureus, targeting a skin protein, leading to skin peeling.
    • Superantigens are proteins that activate a large number of T cells, for example, toxic shock syndrome toxin-1 produced by S. aureus causing toxic shock syndrome.
    • Chronic inflammation can lead to tissue damage due to the release of reactive oxygen species and proteolytic enzymes, and antibodies, in some cases, can contribute to damage.
    • Bacteria avoid host defenses through capsule formation, antigenic variation, biofilm formation, and mimicry.
    • Terminology related to pathogenesis includes ID50, incubation period, prodromal symptoms, convalescence, carriers, virulence, virulence factors, opportunistic infections, symptoms vs. signs, infection vs. colonization, primary pathogen, primary infections, and secondary infection.
    • The Human Microbiome Project aimed to identify major organisms in the human microbiota, determine associations between microbiota changes and diseases, and develop tools for microbiota studies.
    • The gut harbors a vast and diverse microbial community, with trillions of microorganisms, including bacteria, viruses, fungi, and archaea.
    • The five major bacterial phyla dominating the gut microbiota are Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria, and Verrucomicrobia, and their relative abundance can shift in response to environmental cues.

    Epidemiology and Immunity: Key Concepts

    • Endemic diseases are constantly present in a population, while an outbreak is a higher than expected cluster of disease cases over a specific time.
    • Reservoir is the natural habitat where a pathogen lives, and a vector is a living organism that can carry and transmit a pathogen.
    • Contact tracing involves aggressively tracking down individuals exposed to a contagious disease to prevent further spread.
    • Vertical transmission occurs from pregnant woman to fetus or mother to infant during childbirth, while horizontal transmission occurs person to person via air, physical contact, ingestion, or vector.
    • Mechanisms of spread include fomites, droplet transmission, and droplet nuclei, and natural, transmission, and terminal hosts play different roles in pathogen life cycles.
    • Prospective, cross-sectional, and retrospective studies predict, identify associations, and compare actions following an outbreak, respectively.
    • Pathogen and host characteristics such as virulence, dose, immunity, and age influence disease epidemiology.
    • Descriptive studies collect data, analytical studies determine risk factors, and experimental studies involve cause and effect studies.
    • Common-source epidemics stem from exposure to a single source, while propagated epidemics indicate contagious disease spreading in the population.
    • Many emerging human infectious diseases have a zoonotic origin, transmitted from animals to humans.
    • Human, environmental, and microbial factors contribute to the emergence of diseases, and scenarios can be classified based on various factors.
    • First-line defenses are physical and chemical barriers, innate immune responses are immediate and non-specific, and adaptive immune responses are specific and involve B and T lymphocytes.

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