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?

Synthesizing amino acids and vitamins Signup and view all the answers

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

300 to 400 Signup and view all the answers

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

Source of protein Signup and view all the answers

What type of metabolic reactions do rumen microorganisms perform?

Fermentation Signup and view all the answers

What enables cattle to eat a more varied diet?

Detoxification of plant metabolites by rumen microorganisms 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?

Leghemoglobin Signup and view all the answers

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

Recognition and attachment of bacterium to root hairs 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?

Ectomycorrhizae Signup and view all the answers

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

Endomycorrhizae Signup and view all the answers

What is the main role of mycorrhizal fungi in plants?

Improve nutrient absorption Signup and view all the answers

Which group of insects decompose cellulose and hemicellulose?

Termites Signup and view all the answers

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

Foregut fermentation Signup and view all the answers

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

Rumen Signup and view all the answers

What is the main energy source for ruminant animals?

Volatile fatty acids Signup and view all the answers

Which of the following best describes lichens?

Mutualistic relationship between a fungus and an alga Signup and view all the answers

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

Providing a structure and protection for the alga Signup and view all the answers

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

Formation of root nodules that fix nitrogen Signup and view all the answers

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

They have the ability to fix nitrogen Signup and view all the answers

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

Oxygen Signup and view all the answers

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

They are inactivated Signup and view all the answers

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

Nitrogen fixation Signup and view all the answers

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

Enhancing nutrient uptake for the plant Signup and view all the answers

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

rhizobia Signup and view all the answers

Plant root nodules are:

sites here nitrogen-fixing occurs Signup and view all the answers

Where are ectomycorrhizae most highly developed and where?

outside cell, on boreal and temperate forests Signup and view all the answers

Where are endomycorrhizae found and developed?

inside root tissue, terrestrial plants Signup and view all the answers

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

the AM increases the total surface area to absorb more nutrients Signup and view all the answers

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

anaerobic/ cellulolytic and fermentative bacterium Signup and view all the answers

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

fungus protects photosynthetic partner from erosion 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.