32 Questions
Which microorganisms dominate in the rumen?
Anaerobic bacteria
Rumen acidification can occur as a result of what?
Changes in the rumen flora
What is the potential consequence of rumen acidification?
Inflammation of the rumen
What is the role of rumen microbes in the diet of ruminant animals?
Synthesizing amino acids and vitamins
How many bacterial 'species' are found in the rumen?
300 to 400
What can rumen microorganisms serve as to their host when directly digested?
Source of protein
What type of metabolic reactions do rumen microorganisms perform?
Fermentation
What enables cattle to eat a more varied diet?
Detoxification of plant metabolites by rumen microorganisms
Which protein in the nodule binds up free oxygen and serves as an 'oxygen buffer' to protect nitrogenases from free oxygen?
Leghemoglobin
What is the function of Nod factors excreted by rhizobia during root nodule formation?
Recognition and attachment of bacterium to root hairs
Which type of mycorrhizae remains outside the plant roots and forms an extensive sheath around the outside of the root?
Ectomycorrhizae
Which type of mycorrhizae becomes deeply embedded within the root tissue and is called arbuscular mycorrhizae?
Endomycorrhizae
What is the main role of mycorrhizal fungi in plants?
Improve nutrient absorption
Which group of insects decompose cellulose and hemicellulose?
Termites
Which type of fermentation chamber precedes the small intestine in herbivorous animals?
Foregut fermentation
Which digestive organ in ruminants is responsible for digesting cellulose with the help of microbes?
Rumen
What is the main energy source for ruminant animals?
Volatile fatty acids
Which of the following best describes lichens?
Mutualistic relationship between a fungus and an alga
What is the main function of the fungus in a lichen symbiosis?
Providing a structure and protection for the alga
What is the result of legume roots being infected by nitrogen-fixing bacteria?
Formation of root nodules that fix nitrogen
Why do nodulated legumes grow well in areas where other plants would not?
They have the ability to fix nitrogen
What is the main requirement for nitrogen-fixing bacteria to generate energy for nitrogen fixation?
Oxygen
What happens to the nitrogen-fixing enzymes in the presence of oxygen?
They are inactivated
Which of the following is NOT a type of microbial symbiosis discussed in the text?
Nitrogen fixation
What is the role of mycorrhizae in plant-microbial symbiosis?
Enhancing nutrient uptake for the plant
Most nitrogen-fixing bacteria symbiotically associated with plants are called?
rhizobia
Plant root nodules are:
sites here nitrogen-fixing occurs
Where are ectomycorrhizae most highly developed and where?
outside cell, on boreal and temperate forests
Where are endomycorrhizae found and developed?
inside root tissue, terrestrial plants
How do arbuscular mycorrhizae (AM) help plants obtain more nutrients from the soil?
the AM increases the total surface area to absorb more nutrients
The rumen is an ( ) habitat that depends on ( ) to digest cellulose for ruminant animals
anaerobic/ cellulolytic and fermentative bacterium
lichens are a mutualistic association of a fungus and either an alga or a cyanobacterium in which:
fungus protects photosynthetic partner from erosion
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
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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