Microbial Symbioses with Microbes, Plants, and Animals (Lec 16)
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Questions and Answers

Which microorganisms dominate in the rumen?

  • Fungi
  • Protozoa
  • Aerobic bacteria
  • Anaerobic bacteria (correct)
  • Rumen acidification can occur as a result of what?

  • Direct digestion of rumen microbes
  • Feeding on a varied diet
  • Changes in the rumen flora (correct)
  • Detoxification of plant metabolites
  • What is the potential consequence of rumen acidification?

  • Detoxification of plant metabolites
  • Inflammation of the rumen (correct)
  • Increased production of amino acids
  • Synthesis of vitamins by rumen microbes
  • What is the role of rumen microbes in the diet of ruminant animals?

    <p>Synthesizing amino acids and vitamins</p> Signup and view all the answers

    How many bacterial 'species' are found in the rumen?

    <p>300 to 400</p> Signup and view all the answers

    What can rumen microorganisms serve as to their host when directly digested?

    <p>Source of protein</p> Signup and view all the answers

    What type of metabolic reactions do rumen microorganisms perform?

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

    What enables cattle to eat a more varied diet?

    <p>Detoxification of plant metabolites by rumen microorganisms</p> Signup and view all the answers

    Which protein in the nodule binds up free oxygen and serves as an 'oxygen buffer' to protect nitrogenases from free oxygen?

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

    What is the function of Nod factors excreted by rhizobia during root nodule formation?

    <p>Recognition and attachment of bacterium to root hairs</p> Signup and view all the answers

    Which type of mycorrhizae remains outside the plant roots and forms an extensive sheath around the outside of the root?

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

    Which type of mycorrhizae becomes deeply embedded within the root tissue and is called arbuscular mycorrhizae?

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

    What is the main role of mycorrhizal fungi in plants?

    <p>Improve nutrient absorption</p> Signup and view all the answers

    Which group of insects decompose cellulose and hemicellulose?

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

    Which type of fermentation chamber precedes the small intestine in herbivorous animals?

    <p>Foregut fermentation</p> Signup and view all the answers

    Which digestive organ in ruminants is responsible for digesting cellulose with the help of microbes?

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

    What is the main energy source for ruminant animals?

    <p>Volatile fatty acids</p> Signup and view all the answers

    Which of the following best describes lichens?

    <p>Mutualistic relationship between a fungus and an alga</p> Signup and view all the answers

    What is the main function of the fungus in a lichen symbiosis?

    <p>Providing a structure and protection for the alga</p> Signup and view all the answers

    What is the result of legume roots being infected by nitrogen-fixing bacteria?

    <p>Formation of root nodules that fix nitrogen</p> Signup and view all the answers

    Why do nodulated legumes grow well in areas where other plants would not?

    <p>They have the ability to fix nitrogen</p> Signup and view all the answers

    What is the main requirement for nitrogen-fixing bacteria to generate energy for nitrogen fixation?

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

    What happens to the nitrogen-fixing enzymes in the presence of oxygen?

    <p>They are inactivated</p> Signup and view all the answers

    Which of the following is NOT a type of microbial symbiosis discussed in the text?

    <p>Nitrogen fixation</p> Signup and view all the answers

    What is the role of mycorrhizae in plant-microbial symbiosis?

    <p>Enhancing nutrient uptake for the plant</p> Signup and view all the answers

    Most nitrogen-fixing bacteria symbiotically associated with plants are called?

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

    Plant root nodules are:

    <p>sites here nitrogen-fixing occurs</p> Signup and view all the answers

    Where are ectomycorrhizae most highly developed and where?

    <p>outside cell, on boreal and temperate forests</p> Signup and view all the answers

    Where are endomycorrhizae found and developed?

    <p>inside root tissue, terrestrial plants</p> Signup and view all the answers

    How do arbuscular mycorrhizae (AM) help plants obtain more nutrients from the soil?

    <p>the AM increases the total surface area to absorb more nutrients</p> Signup and view all the answers

    The rumen is an ( ) habitat that depends on ( ) to digest cellulose for ruminant animals

    <p>anaerobic/ cellulolytic and fermentative bacterium</p> Signup and view all the answers

    lichens are a mutualistic association of a fungus and either an alga or a cyanobacterium in which:

    <p>fungus protects photosynthetic partner from erosion</p> Signup and view all the answers

    Study Notes

    Rumen Microorganisms

    • Bacteria, protozoa, and fungi dominate in the rumen of ruminant animals
    • Rumen acidification occurs as a result of excessive fermentation of non-structural carbohydrates
    • Potential consequence of rumen acidification is a decrease in fiber digestion and microbial growth

    Rumen Microbes' Role

    • Rumen microbes break down cellulose, proteins, and other dietary components in the rumen
    • There are approximately 1,000 to 1,500 bacterial 'species' found in the rumen
    • Rumen microorganisms can serve as a source of protein for their host when directly digested
    • Rumen microorganisms perform fermentation reactions, producing volatile fatty acids as energy sources

    Nitrogen Fixation

    • Legume roots become infected by nitrogen-fixing bacteria, which form root nodules
    • Nod factors excreted by rhizobia during root nodule formation trigger the plant's response
    • The protein leghemoglobin in the nodule binds up free oxygen and serves as an 'oxygen buffer' to protect nitrogenases from free oxygen
    • Nitrogen-fixing bacteria require energy generated from the plant to fix atmospheric nitrogen

    Mycorrhizal Fungi

    • Ectomycorrhizae remain outside the plant roots and form an extensive sheath around the root
    • Endomycorrhizae (arbuscular mycorrhizae) become deeply embedded within the root tissue
    • Mycorrhizal fungi aid plants in obtaining more nutrients from the soil
    • Main role of mycorrhizal fungi is to facilitate nutrient uptake by plants

    Insects and Fermentation

    • Insects, such as termites, decompose cellulose and hemicellulose
    • The rumen precedes the small intestine in herbivorous animals and is responsible for digesting cellulose with microbial help
    • The main energy source for ruminant animals is volatile fatty acids produced through fermentation

    Lichens

    • Lichens are a mutualistic association of a fungus and either an alga or a cyanobacterium
    • The main function of the fungus in a lichen symbiosis is to provide protection and structure
    • Lichens can thrive in environments where other organisms cannot survive due to their symbiotic association

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    Description

    Test your knowledge on microbial symbioses with this quiz. Explore the fascinating world of lichens, their habitats, and their symbiotic relationships with other organisms.

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