General Microbiology - BIOL 336 AO Quiz
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Questions and Answers

Which of the following statements about microorganisms is incorrect?

  • They are life forms too small to be seen by the naked eye.
  • They are a significant portion of Earth's biomass.
  • They are all single-celled organisms. (correct)
  • They exist in a vast array of forms and functions.

    • Microorganisms often live in groups called:

  • Colonies
  • Communities (correct)
  • Biomes
  • Ecosystems

    • What is a key characteristic of microbial colonies?

  • They are only formed in liquid environments.
  • They are formed by the growth of microorganisms in a nutrient medium. (correct)
  • They are visible to the naked eye only under a microscope.
  • They are always harmful to humans.

    • Which of these is NOT a characteristic that makes microorganisms excellent model organisms for scientific study?

    <p>Their genetic material is different from that of larger organisms. (D)</p> Signup and view all the answers

    What is the main principle of the quote: 'What is true of elephants is also true of bacteria, and bacteria are much easier to study'?

    <p>Bacteria are a good model for understanding fundamental biological processes. (C)</p> Signup and view all the answers

    What is the estimated age of the first anoxygenic phototrophs?

    <p>~3.6 billion years ago (D)</p> Signup and view all the answers

    What is the estimated age of the first plants and animals?

    <p>~0.5 billion years ago (D)</p> Signup and view all the answers

    From where did the three distinct lineages of microbial cells descend?

    <p>A common ancestor (D)</p> Signup and view all the answers

    What is the study of microbes in their natural environment called?

    <p>Microbial ecology (B)</p> Signup and view all the answers

    What is the approximate ratio of microbial cells to human cells in the human body?

    <p>1:10 (C)</p> Signup and view all the answers

    Which of the following is NOT an example of an extremophile habitat?

    <p>Tropical rainforests (A)</p> Signup and view all the answers

    What is the primary way microorganisms impact human society?

    <p>All of the above (D)</p> Signup and view all the answers

    How have microorganisms been used in human history?

    <p>All of the above (D)</p> Signup and view all the answers

    How does a phase-contrast microscope improve the contrast of unstained cells?

    <p>It amplifies differences in the refractive index between the cell and its surroundings. (B)</p> Signup and view all the answers

    Which type of microscopy is particularly useful for visualizing the internal structures of cells, even those that are unstained and alive?

    <p>Phase-contrast microscopy (A)</p> Signup and view all the answers

    What is the primary advantage of using a transmission electron microscope (TEM) over a light microscope?

    <p>TEMs provide higher resolution images, allowing for visualization of smaller structures. (A)</p> Signup and view all the answers

    In a TEM image, what does a dark area typically represent?

    <p>An area of the specimen that absorbs the electron beam. (A)</p> Signup and view all the answers

    Which of the following techniques relies on a computer to compile images from different layers of a specimen to construct a 3D image?

    <p>Confocal scanning laser microscopy (CSLM) (C)</p> Signup and view all the answers

    What is the difference between prokaryotic and eukaryotic cells?

    <p>Eukaryotes have membrane-bound organelles while prokaryotes do not. (C), Eukaryotes have a nucleus while prokaryotes do not. (D)</p> Signup and view all the answers

    What is the function of ribosomes in both prokaryotic and eukaryotic cells?

    <p>Ribosomes are responsible for the synthesis of proteins. (B)</p> Signup and view all the answers

    What is the difference between a prokaryotic chromosome and a eukaryotic chromosome?

    <p>A prokaryotic chromosome is circular, while a eukaryotic chromosome is linear. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic shared by both prokaryotic and eukaryotic cells?

    <p>Mitochondria (D)</p> Signup and view all the answers

    What is a genome?

    <p>A genome is a cell's full complement of genes. (C)</p> Signup and view all the answers

    Which is a characteristic specific to a prokaryotic cell, but not a eukaryotic cell?

    <p>Nucleoid region (D)</p> Signup and view all the answers

    What is the key difference between a plasmid and a chromosome in a prokaryotic cell?

    <p>A chromosome is essential for survival while a plasmid is not. (B)</p> Signup and view all the answers

    What is a major consequence of the development of oxygenic photosynthesis on Earth?

    <p>The atmosphere became oxygenic. (A)</p> Signup and view all the answers

    What is the smallest size an object can be and still be seen with a light microscope?

    <p>0.2 μm (D)</p> Signup and view all the answers

    What did Robert Hooke describe in 1665?

    <p>Microorganisms in bread mold (D)</p> Signup and view all the answers

    Which of the following is NOT a positive impact of microorganisms in food production?

    <p>Causing food spoilage (D)</p> Signup and view all the answers

    Which of these is an example of industrial microbiology?

    <p>Growing large quantities of naturally-occurring microbes to produce antibiotics (C)</p> Signup and view all the answers

    What is the term for the growth of microorganisms on submerged surfaces?

    <p>Biofilms (A)</p> Signup and view all the answers

    What is the main difference between industrial microbiology and biotechnology?

    <p>Industrial microbiology focuses on natural microbes, while biotechnology uses genetically engineered microbes (D)</p> Signup and view all the answers

    Which of the following is NOT a factor that can influence harvest, storage, and safety of food?

    <p>Biotechnology (A)</p> Signup and view all the answers

    What is the main concept that connects the examples of bioterrorism, food spoilage, and biofilms?

    <p>The potential for microorganisms to be used for both good and bad purposes (C)</p> Signup and view all the answers

    What is the approximate resolving power of an electron microscope?

    <p>0.3 nm (C)</p> Signup and view all the answers

    Which of the following is NOT true about scanning electron microscopy (SEM)?

    <p>It produces a two-dimensional image of the sample's surface. (B)</p> Signup and view all the answers

    According to the provided text, what did Francesco Redi's rotting meat experiment aim to disprove?

    <p>The theory of spontaneous generation. (B)</p> Signup and view all the answers

    What was Louis Pasteur's key contribution to the understanding of microorganisms?

    <p>He showed that air is filled with microorganisms. (B)</p> Signup and view all the answers

    What is the significance of Robert Koch's work in the field of microbiology?

    <p>He identified the causative agents of several infectious diseases. (C)</p> Signup and view all the answers

    What is the unique feature of ribosomal RNA (rRNA) that made it useful for building the first tree of life?

    <p>It is highly conserved and present in all cells. (A)</p> Signup and view all the answers

    What is the root of the phylogenetic tree, according to the provided text?

    <p>The last universal common ancestor (LUCA). (B)</p> Signup and view all the answers

    Which of the following is NOT directly mentioned in the text as one of the three domains of life?

    <p>Prokaryotes (D)</p> Signup and view all the answers

    What is the main implication of the statement that "most microbes have not been cultured yet"?

    <p>Our current understanding of microbial diversity is incomplete. (B)</p> Signup and view all the answers

    Study Notes

    General Microbiology

    • BIOL 336 AO, Spring 2025 course taught by Dr. Purple
    • Office: MANS 334
    • Email: [email protected]

    The Microbial World

    • Microorganisms (microbes) are life forms too small to be seen by the human eye
    • Diverse in form and function
    • Major fraction of Earth's biomass
    • Many are single-celled, some form complex structures, and some are multicellular
    • Live in microbial communities

    Studying Microbes

    • Microscopy is used to view individual microbes
    • Culture involves growing cells in or on nutrient mediums
    • A medium is a liquid or solid mixture containing all required nutrients, that promotes growth to form visible colonies

    Microbial Colonies

    • A microbial colony is a visible cluster of microorganisms viewed with the naked eye
    • Colonies form from individual bacteria growing in a medium

    Microbes as Model Organisms

    • All cells are composed of the same elements
    • Cells replicate DNA

    Prokaryotic vs. Eukaryotic Cells

    • Prokaryotes include bacteria and archaea
    • Lack membrane-enclosed organelles and nuclei
    • Eukaryotes include plant, animal, fungi, protists, and algae
    • Possess membrane-enclosed organelles and a nucleus

    Elements of Microbial Structure

    • All cells share cytoplasmic (cell) membranes, cytoplasm, ribosomes, and may have a cell wall

    Genes, Genomes, Nucleus, and Nucleoid

    • Genome: A cell's full set of genes
    • Prokaryotic DNA is generally single, circular chromosomes aggregating into the nucleoid region
    • Can also have plasmids (extrachromosomal DNA) conferring special properties like antibiotic resistance
    • Prokaryotic DNA is compact (0.5-10 million base pairs)
    • Eukaryotic DNA is linear and contained within the nucleus, much larger (up to billions of base pairs)

    Microbial Cell Activities

    • Metabolism: Cells take up nutrients, modify them and expel wastes
    • Growth: Nutrients are converted into new cell materials.
    • Differentiation: Some cells form new structures such as spores
    • Communication: Cells interact through chemical signals
    • Evolution: Cells develop new traits.
    • Genetic exchange: Cells transfer genes.

    Microorganisms and the Biosphere

    • Earth is 4.6 billion years old
    • First cells appeared 3.8-4.3 billion years ago
    • The atmosphere was initially anoxic (no oxygen)
    • Early lifeforms used anaerobic metabolisms and were photosynthetic (anoxic)
    • Plants and animals appeared approximately 0.5 billion years ago

    Domains and Extremophiles

    • Domains are distinct lineages of microbial cells
    • Extremophiles live in extreme habitats (hot springs, glaciers)
    • Microbial metabolic activities change habitats and affect other organisms

    The Impact of Microorganisms on Human Society

    • Microorganisms as disease agents
    • Control of infectious diseases over the last century
    • Bacterial and viral pathogens
    • Negative impacts of microbes on food: food spoilage and foodborne disease
    • Positive impacts of microbes on food: improving food safety and preservation (dairy products, cheeses, yogurt, buttermilks, sauerkraut, kimchi, pickles, chocolate, coffee, leavened breads, beer)
    • Microbes and industry, including biofilms (growth on surfaces like pipes, tanks, implanted medical devices) and industrial microbiology (growth to make low-cost products like antibiotics, enzymes). Biotechnology involving genetically engineered microbes that produce high-value products.
    • Bioterrorism: Microbes have been used as weapons in the past.

    Microbiology History

    • Antony van Leeuwenhoek: Invented magnifying glasses to view animalcules
    • Robert Hooke: Described microscopical mushrooms (common bread mold)
    • Louis Pasteur: Disproved spontaneous generation
    • Robert Koch: Demonstrated link between microbes and infectious diseases, discovered causative agents for anthrax, tuberculosis and cholera.

    Microscopy

    • Light Microscopy: Light passes through the specimen
    • Bright-field microscope, Fluorescent microscopy
    • Electron Microscopy: Has high resolving power that allows viewing smaller details
    • Transmission Electron Microscopy (TEM): Beam of electrons pass through the sample
    • Scanning Electron Microscopy (SEM): Beam of electrons scan the sample's surface

    Improving Contrast in Light Microscopy

    • Staining increases contrast in light microscopy
    • Differential stains distinguish different cell types (e.g., Gram stain)
    • Phase-contrast microscopy improves image contrast of unstained, live cells

    Imaging Cells in Three Dimensions

    • Confocal scanning laser microscopy (CSLM) allows for creating 3D images of a specimen by focusing a laser on single layers.

    Postulates

    • Koch's Postulates are experimental steps confirming the causative link between a suspected pathogen and a disease

    Woese and the Tree of Life

    • Carl Woese recognized rRNA sequences for phylogenetic relationships
    • Named the new group Archaea
    • Phylogenetic trees depict evolutionary histories, showing three domains (Bacteria, Archaea, Eukarya)

    Introduction to Microbial Life

    • Bacteria: Prokaryotes, single cells, diverse, vary in size and shape
    • Archaea: Prokaryotes, less morphological diversity, often associated with extreme environments
    • Eukarya: Plant, animal, fungi, algae, protozoa, diverse in size and structure.
    • Viruses: Obligate parasites, do not carry out metabolism, vary dramatically in composition

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    Description

    This quiz covers essential concepts in General Microbiology as taught in the BIOL 336 AO course. Explore the diversity of microorganisms, methods of studying them, and the differences between prokaryotic and eukaryotic cells. Test your understanding of microbial structures and functions.

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