Microbiology: Morphological Characteristics
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Microbiology: Morphological Characteristics

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Questions and Answers

Which of the following characteristics is NOT associated with the phylum Crenarchaeota?

  • Dependent on sulfur for respiration
  • Mesophilic metabolism (correct)
  • Extreme thermophiles
  • Strict anaerobes

    • What type of metabolism do Thaumarchaeota primarily exhibit?

  • Sulfur reduction
  • Ammonia oxidation (correct)
  • Lactic acid production
  • Fermentation of organic compounds

    • Which genus is part of the Order Desulfurococcales within the Crenarchaeota?

  • Methanococcus
  • Methanobrevibacter
  • Pyrodictium (correct)
  • Sulfolobus

    • Which of the following statements about Sulfolobus is TRUE?

    <p>It grows lithotrophically on sulfur granules.</p> Signup and view all the answers

    Where are the organisms of the phylum Euryarchaeota primarily found?

    <p>Lower temperature niches</p> Signup and view all the answers

    What is the typical temperature range for members of the Crenarchaeota phylum?

    <p>84 – 110 oC</p> Signup and view all the answers

    Which of the following metabolic processes can be used by sulfur-utilizing members of Crenarchaeota?

    <p>Lithotrophic oxidation of sulfur</p> Signup and view all the answers

    What type of environments do Thaumarchaeota usually inhabit?

    <p>Soils and varied aquatic environments</p> Signup and view all the answers

    What type of lipid forms a monolayer in archaeal cell membranes?

    <p>Diglycerol tetraether lipids</p> Signup and view all the answers

    Which factor contributes to the stability of archaeal monolayers?

    <p>Presence of unique lipids</p> Signup and view all the answers

    How does the chromosome size of some archaea compare to that of eubacteria?

    <p>They are significantly smaller in some cases.</p> Signup and view all the answers

    Which electron carrier is primarily used by autotrophic archaea?

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

    Which of the following pathways is characterized as reductive acetyl-CoA?

    <p>Associated mainly with methanogens</p> Signup and view all the answers

    Which of these archaea are known to utilize the 3-hydroxyproprionate/4-hydroxybutyrate pathway?

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

    The G+C content in archaea can vary between which percentages?

    <p>21% to 68%</p> Signup and view all the answers

    Which group of archaea predominantly uses the dicarboxylate/4-hydroxybutyrate pathway?

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

    What shape is Escherichia coli?

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

    What color does Bacillus subtilis' vegetative cells stain?

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

    Which of the following characteristics are major morphological characteristics?

    <p>Cell shape</p> Signup and view all the answers

    Corynebacterium diphtheriae is described as which shape?

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

    What does the staining behavior reveal about Staphylococcus aureus?

    <p>It is gram-positive</p> Signup and view all the answers

    What is the primary purpose of using stains in microbiology?

    <p>To visualize and group microbes</p> Signup and view all the answers

    Which bacterium is known to cause anthrax?

    <p>Bacillus anthracis</p> Signup and view all the answers

    What microscopy technique is used to study the ultrastructure of microbes?

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

    What type of metabolism do Nitrosomonas and their related genera exhibit?

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

    What is the primary role of Thiobacillus denitrificans in its environment?

    <p>Mobilization of precious metals</p> Signup and view all the answers

    Which reaction describes the process of nitrification involving ammonium?

    <p>NH4+ → NO2- → NO3-</p> Signup and view all the answers

    What is the key electron donor for Thiobacillus?

    <p>Hydrogen sulfide</p> Signup and view all the answers

    In which environment is Thiobacillus denitrificans predominantly found?

    <p>Acid mine drainage</p> Signup and view all the answers

    Which of the following statements about Bordetella bronchiseptica is true?

    <p>It can cause kennel cough in dogs.</p> Signup and view all the answers

    Which of the following best describes the term 'co-anammox'?

    <p>Direct conversion of NH4+ to NO3-</p> Signup and view all the answers

    What type of bacteria are classified as colorless sulfur bacteria?

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

    What is a distinctive feature of nonproteobacterial Gram-negative bacteria?

    <p>Morphologically unique and compartmentalized cells</p> Signup and view all the answers

    In the anammox reaction, what role does nitrite play?

    <p>It acts as a terminal electron acceptor</p> Signup and view all the answers

    What is the primary function of the anammoxosome in nonproteobacterial Gram-negative bacteria?

    <p>It is involved in ATP production via anammox reaction</p> Signup and view all the answers

    Which of the following is true concerning the electron transport in the anammox reaction?

    <p>Ferredoxin is reduced and donates electrons to hydrazine</p> Signup and view all the answers

    What components contribute to the formation of the proton motive force (PMF) in nonproteobacterial Gram-negative bacteria?

    <p>Electron shuttling and proton pumping</p> Signup and view all the answers

    What is the significance of hydrazine (N2H4) in the anammox reaction?

    <p>It donates electrons to ferredoxin</p> Signup and view all the answers

    Which reaction represents the anabolic part of the anammox process?

    <p>2NO2- + CO2 + H2O → CH2O + 2NO3-</p> Signup and view all the answers

    Which genera are associated with nonproteobacterial Gram-negative bacteria?

    <p>Brociadia, Kuenenia, Scalindua, and Anammoxoglobus</p> Signup and view all the answers

    Study Notes

    Morphological Characteristics

    • Shape, size, and staining behaviour are key identifiers of microorganisms
    • Gram staining classifies bacteria as gram-positive (purple) or gram-negative (pink)
    • Light microscopes are useful for analyzing larger cellular structures
    • Transmission electron microscopy (TEM) is used to analyze smaller structures, such as the morphology of organelles within cells

    Escherichia coli

    • Rod-shaped
    • Gram-negative
    • Commonly used in laboratory research

    Staphylococcus aureus

    • Coccus shaped
    • Gram-positive
    • Known to microbiologists due to strains used in laboratory research

    Bacillus subtilis

    • Gram-positive
    • Green-stained spores indicate dormant cells
    • Red-stained vegetative cells are actively growing

    Bacillus anthracis

    • Gram-positive
    • Rod-shaped
    • Causes anthrax
    • Historically developed as a biological weapon

    Corynebacterium diphtheria

    • Gram-positive
    • Club-shaped
    • Causes diphtheria

    Archaeal Cell Membranes

    • Can form monolayers instead of bilayers
    • The monolayer functions as a bilayer
    • Monolayers are formed due to unique lipids in archaeal plasma membranes
    • Two major archaeal lipids:
      • Glycerol diether lipids: form a typical bilayer
      • Diglycerol tetraether lipids: form a monolayer, providing greater stability and prevalent in thermophiles

    Archaeal Genetics and Molecular Biology

    • Some archaeal chromosomes are smaller than those of eubacteria
    • The G+C content of archaeal DNA varies between 21% and 68%
    • Archaeal ribosomes, mRNA, and RNA polymerases have distinctive properties

    Archaeal Metabolism

    • Most known autotrophic archaea thrive in anaerobic or low-oxygen conditions
    • They use ferredoxin (Fd) instead of NADPH as electron carriers
    • Three main carbon fixation pathways:
      • Reductive acetyl-CoA pathway: used by methanogens for carbon fixation and energy production, and by other archaea for carbon fixation
      • 3-hydroxyproprionate/4-hydroxybutyrate pathway: found in crenarchaeotes like Sulfolobales and Thaumarchaeota, operating under aerobic conditions
      • Dicarboxylate/4-hydroxybutyrate pathway: present in crenarchaeotes like Thermoproteales and Desulfurococcales, includes reductive TCA steps

    Archaeal Taxonomy

    • Three main phyla based on rRNA data:
      • Crenarchaeota
      • Thaumarchaeota
      • Euryarchaeota

    Crenarchaeota

    • All are thermophiles or hyperthermophiles
    • Mostly strict anaerobes
    • Acidophiles dependent on sulfur
    • Sulfur acts as both an electron acceptor during anaerobic respiration and an electron donor in lithotrophs
    • Found in geothermally heated water or sulfur-containing soil

    Thaumarchaeota

    • Found in soils and aquatic environments
    • Mesophiles
    • Ammonia oxidizers

    Euryarchaeota

    • Occupy lower temperature niches
    • Examples: Methanogens, extreme halophiles, sulfate utilizers, and extreme thermophiles with sulfur-dependent metabolisms

    Planctomycetes

    • Anaerobic
    • Morphologically unique bacteria with compartmentalized cells
    • Cell wall lacks peptidoglycan
    • Contain a large internal compartment – the intracytoplasmic membrane – separated from the plasma membrane by a ribosome-free region called the paryphoplasm
    • Genera like Brociadia, Kuenenia, Scalindua, and Anammoxoglobus contain an additional compartment called the anammoxosome
    • The anammoxosome is the site of the energy-yielding anammox reaction

    The Anammox Reaction

    • Anaerobic ammonia oxidation (anammox)
    • Ammonium (NH4+) acts as an electron donor
    • Nitrite (NO2-) acts as a terminal electron acceptor
    • NO2- is reduced to nitrogen gas (N2)
    • Hydrazine (N2H4) is a key intermediate, donating electrons to ferredoxin, initiating the electron shuttling that drives proton pumping across the anammoxosome membrane and produces a proton motive force (PMF)

    Bordetella bronchiseptica

    • Motile
    • Coccobacillus shape
    • Causes kennel cough in dogs

    Nitrosomonadales

    • Genera: Nitrosomonas, Nitrosococcus, and Nitrospira
    • Chemoautotrophs
    • Nitrification: oxidise nitrate to nitrite (AMO and HAO enzymes)
    • When present together in soil, Nitrosomonas and Nitrobacter convert ammonia into nitrate through nitrification:
      • NH4+ → NO2- → NO3-
    • Co-anammox describes the direct conversion of NH4+ to NO3-, which doesn't occur in this case due to the separate reactions

    Hydrogenophilales

    • Genus: Thiobacillus
    • Colourless (“colourless sulfur bacteria")
    • Chemolithotrophs
    • Not photosynthetic
    • Electron donor: Reduced inorganic sulfur compounds
    • Electron acceptor: O2

    Thiobacillus denitrificans

    • Found in acid mine drainage
    • Denitrification: reduces nitrate to nitrogen gas
    • Electron donors: Hydrogen sulfide (H2S), thiosulphate (S2O32-), or ferrous iron (Fe2+)
    • Electron acceptor: Oxygen or nitrate
    • Plays a role in biomining by oxidizing metals and solubilizing sulfide ores, facilitating the extraction of precious metals.

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    Description

    This quiz focuses on the morphological characteristics of various microorganisms, including shape, size, and staining behaviors. It covers key examples such as Escherichia coli, Staphylococcus aureus, and Bacillus anthracis, emphasizing their gram classification and significance in laboratory research.

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