Basic Microbiology Lecture - 12
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Questions and Answers

What distinguishes rickettsias from most other bacteria?

  • They reproduce through binary fission only.
  • They can survive outside a host cell.
  • They are obligate intracellular parasites. (correct)
  • They are larger than most bacteria.

    • Which of the following diseases is caused by a rickettsial infection?

  • Tuberculosis
  • Cholera
  • Typhoid fever
  • Rocky Mountain spotted fever (correct)

    • What is a characteristic of chlamydias that differentiates them from rickettsias?

  • They can carry out metabolism independently.
  • They are not closely related to rickettsias. (correct)
  • They are transmitted by arthropods.
  • They have a motile lifestyle.

    • What is the size range of rickettsias?

    <p>0.3 to 0.6 μm wide and 0.8 to 2.0 μm long</p> Signup and view all the answers

    What type of cell wall do rickettsias possess?

    <p>Thin Gram-negative cell wall</p> Signup and view all the answers

    Which of the following statements about rickettsias is true?

    <p>They alternate between mammalian hosts and blood-sucking arthropods.</p> Signup and view all the answers

    How do chlamydias reproduce?

    <p>By binary fission, a prokaryotic method</p> Signup and view all the answers

    Which feature is NOT associated with rickettsias?

    <p>Ability to survive outside host cells</p> Signup and view all the answers

    What characteristic distinguishes chlamydias from mycoplasmas?

    <p>Chlamydias are obligate parasites.</p> Signup and view all the answers

    Which of the following is true about mycoplasmas?

    <p>They can be cultivated on artificial media.</p> Signup and view all the answers

    What aspect of mycoplasmas helps them resist lysis?

    <p>Stabilization of the cell membrane by sterols.</p> Signup and view all the answers

    Which of the following statements about Chlamydia trachomatis is correct?

    <p>It is responsible for trachoma, a type of ocular disease.</p> Signup and view all the answers

    What shape can mycoplasmas exhibit?

    <p>Filamentous, coccus, or doughnut-shaped.</p> Signup and view all the answers

    What is a common habitat for mycoplasmas?

    <p>Found in soil, plants, and animals.</p> Signup and view all the answers

    How does the morphology of chlamydias compare to mycoplasmas?

    <p>Chlamydias exhibit pleomorphic forms, similar to mycoplasmas.</p> Signup and view all the answers

    Which of the following is false regarding mycoplasmas?

    <p>They must obtain nutrients exclusively from host cells.</p> Signup and view all the answers

    What is the primary energy source used by photosynthetic bacteria to synthesize nutrients?

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

    Which of the following characteristics is true of cyanobacteria?

    <p>They range in size from 1 μm to 10 μm.</p> Signup and view all the answers

    What type of bacteria does M. hominis and Ureaplasma urealyticum belong to?

    <p>Mycoplasma and Ureaplasma species</p> Signup and view all the answers

    What is the role of heterocysts in certain cyanobacteria?

    <p>They convert nitrogen gas into a usable form for plants.</p> Signup and view all the answers

    What pigment gives some cyanobacteria a blue tint?

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

    Which feature is a specialized adaptation of cyanobacteria?

    <p>Formation of extensive internal membranes called thylakoids</p> Signup and view all the answers

    Which of the following statements about bacteria is false?

    <p>All bacteria are pathogenic.</p> Signup and view all the answers

    How are photosynthetic bacteria different from most other bacteria?

    <p>They can use sunlight to produce their own food.</p> Signup and view all the answers

    What is the primary method of reproduction in cyanobacteria?

    <p>Binary fission</p> Signup and view all the answers

    Which of the following statements regarding cyanotoxins is accurate?

    <p>Microcystin LR is a type of cyanotoxin.</p> Signup and view all the answers

    How do green and purple sulphur bacteria differ from cyanobacteria?

    <p>They have different types of chlorophyll.</p> Signup and view all the answers

    In which type of environment would you most likely find green sulphur bacteria?

    <p>Anaerobic and sulphide-containing waters</p> Signup and view all the answers

    What characteristic of purple sulphur bacteria allows them to thrive in certain conditions?

    <p>Anaerobic or microaerophilic lifestyle</p> Signup and view all the answers

    What is a notable feature of certain cyanobacteria when they form water blooms?

    <p>They create toxic environments for livestock.</p> Signup and view all the answers

    What type of chlorophyll do green and purple sulphur bacteria possess?

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

    Where do green and purple sulphur bacteria predominantly reside?

    <p>Deep anaerobic waters</p> Signup and view all the answers

    What is the primary characteristic that allows myxobacteria to move over moist surfaces?

    <p>They exhibit the gliding property.</p> Signup and view all the answers

    Under what conditions do myxobacteria produce their fruiting bodies?

    <p>In starvation conditions.</p> Signup and view all the answers

    Which of the following bacteria are known to produce myxospores?

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

    What type of environments do appendaged bacteria typically inhabit?

    <p>Aquatic environments</p> Signup and view all the answers

    What structure do myxobacteria produce that is similar to fungi?

    <p>Fruiting bodies</p> Signup and view all the answers

    What is a common characteristic of the life cycle in myxobacteria?

    <p>Differentiation of vegetative cells into fruiting bodies.</p> Signup and view all the answers

    How do myxobacteria adapt to their environment when food is scarce?

    <p>They form fruiting bodies that produce spores.</p> Signup and view all the answers

    What does the term 'appendaged bacteria' refer to?

    <p>Bacteria that produce a projection from their surface.</p> Signup and view all the answers

    Study Notes

    Basic Microbiology Lecture - 12

    • Lecture focused on prokaryotic groups with unusual characteristics, including medically significant bacteria.

    Survey of Prokaryotic Groups with Unusual Characteristics

    • Covered rickettsias, chlamydias, mycoplasmas, photosynthetic bacteria (including cyanobacteria), and gliding fruiting bacteria (myxobacteria).

    Unusual Forms of Medically Significant Bacteria

    • Rickettsias:
      • Distinctive, very tiny, Gram-negative bacteria.
      • Have a somewhat typical bacterial morphology, but are atypical in their life cycle and other adaptations.
      • Obligate intracellular parasites, needing a host cell for survival.
      • Alternate between mammalian hosts and arthropod vectors (like fleas, lice, or ticks).
      • Cause diseases like Rocky Mountain spotted fever and epidemic typhus.
      • Rickettsia rickettsii causes Rocky Mountain spotted fever, spread by ticks
      • Rickettsia prowazekii causes epidemic typhus, spread by lice.
      • Coxiella burnetti causes Q Fever, is air and dust borne by arthropods.
      • Possess a gram-negative cell wall, divide by binary fission and contain DNA and RNA
      • Among the smallest cells, ranging from 0.3 to 0.6μm wide and 0.8 to 2.0μm long.
      • Non-motile, appearing as pleomorphic rods or coccobacilli
    • Chlamydias:
      • Similar to rickettsias in their requirement for host cells, but unrelated and not requiring arthropod transmission.
      • Obligate intracellular parasites, depending on host cells for crucial metabolic constituents.
      • Share similarities with rickettsias via size, gram-negative cell wall, and pleomorphic morphology.
      • Significant dissimilarities in their life cycles exist
      • Multiply by binary fission
      • Chlamydia trachomatis is a significant pathogen connected to sexually transmitted, neonatal and ocular disease (trachoma), a highly common pathogen.

    Mycoplasmas (Cell-Wall-Deficient Bacteria)

    • Naturally lack a cell wall.
    • Their cell membrane is reinforced by sterols and is resistant to lysis.
    • Extremely small, pleomorphic cells, ranging in size from 0.1 to 0.5µm.
    • Exhibit diverse shapes from filamentous to coccus or doughnut-shaped.
    • Not obligate parasites and can be cultivated on artificial media, but sterols are necessary for cell membranes for some species.
    • Occur in multiple habitats (plants, soil, animals)
    • Implicated in respiratory tract illnesses by various species of Mycoplasma and in various urogenital tract infections by M. hominis and Ureaplasma urealyticum.

    Free-Living Non-Pathogenic Bacteria: Photosynthetic Bacteria

    • Most bacteria derive nutrients from other organisms.
    • Photosynthetic bacteria employ independent cells that contain special light-trapping pigments, converting sunlight to synthesize nutrients from simple inorganic compounds
    • Photosynthetic bacteria can be categorized based on oxygen production during photosynthesis.

    Cyanobacteria (Blue-Green Bacteria)

    • Previously called blue-green algae
    • Have a gram-negative cell wall;
    • Exhibit oxygenic photosynthesis.
    • Contain specialized internal membranes called thylakoids—with chlorophyll pigments and photosynthetic granules.
    • Range in size from 1µm to 10µm, categorized as unicellular or in colonies as filaments, sometimes with gelatinous sheaths.
    • Characterized by gas inclusions, which aid in floating and increasing light exposure.
    • Can form water blooms (Anabaena, Aphanizomenon, Microcystis), which can cause unpleasant odors and even livestock mortality due to toxin production and accumulation of organic matter.
    • They make nitrogen fertilizer usable by plants.
    • Produce cyanotoxins, which can be harmful to humans and animals (e.g., microcystin LR, nodularin R).

    Green and Purple Sulphur Bacteria

    • Photosynthetic bacteria that differ from cyanobacteria in their pigment type (bacteriochlorophyll) and in not producing oxygen during photosynthesis.
    • Live in anaerobic habitats (sulfur springs, freshwater lakes, swamps) where light penetrates deeply enough for their pigments to absorb wavelengths, with deep anaerobic conditions.
    • Occur as single cells, exhibiting varied shapes, and are usually motile.
    • Utilize sulfur compounds (e.g., H₂S, S) for metabolism, sometimes storing sulfur internally as granules.
    • Purple sulphur bacteria are anaerobic or microaerophilic, and green sulphur bacteria are obligate anaerobes.

    Gliding Fruiting Bacteria (Myxobacteria)

    • Myxobacteria, particularly the slime bacteria are interesting and highly unusual.
    • Commonly found in animal dung and organic-rich soils (neutral or alkaline pH).
    • Characterized by a gliding motility mechanism involving the rotation of filaments or fibers under the cell wall's outer membrane.
    • Lack flagella.
    • Have complex life cycles; vegetative cells form multicellular fruiting bodies, producing highly resistant myxospores.
    • Fruiting body structures are often visually apparent (e.g. on tree bark and plant debris).

    Appendaged Bacteria

    • Bacteria such as different stalked types and different budding types have extensions from their surface, some attached tightly and some loosely (like the glycocalyx.)
    • Appendages like stalks or threads can vary in type.
    • Some are aquatic and can trap small organic matter.
    • Budding bacteria reproduce asexually through budding from extended parts of the cell wall.

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    Basic Microbiology Lecture 12 PDF

    Description

    This lecture provides an overview of unusual prokaryotic groups, focusing on medically significant bacteria such as rickettsias and chlamydias. Explore the characteristics and life cycles of these unique microorganisms and their role in human diseases. Enhance your understanding of their interactions with hosts and vectors.

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