Microbes: Enemies and Commensals

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Questions and Answers

Why is the animal body such an attractive environment for microorganisms?

The animal body contains all the components necessary to sustain life. It is warm, moist, and rich in nutrients, making it an ideal environment for microorganisms to thrive and multiply.

In what ways can the commensal microbiota be beneficial to the host animal?

Commensal microbiota help in the proper digestion of food. They also keep the host's defenses in peak operating condition by stimulating the immune system.

Explain why it is crucial for the animal's immune system to be carefully regulated when interacting with the normal microbiota.

The immune system must be carefully regulated to avoid attacking the commensal microbiota. An aggressive response toward these beneficial microbes would cause unnecessary inflammation and harm to the host.

How does the animal body resist microbial invasion?

Living, healthy animals are highly resistant to microbial invasion due to their effective immune defenses. Signup and view all the answers

List three types of dangerous microbial invaders.

Bacteria, viruses, and fungi. Signup and view all the answers

The text describes the magnitude of microbial attack after death. Explain what happens.

The dead body decomposes as bacteria invade its tissues. Signup and view all the answers

Explain the difference between commensal organisms and dangerous microbial invaders.

Commensal organisms share resources with the host and do not cause damage, whereas dangerous microbial invaders exploit the host's resources and cause tissue/cell damage leading to sickness or death. Signup and view all the answers

Give a brief overview of the environment microbes thrive in.

Microbes thrive nearly everywhere - in the air, water, soil, homes, bodies and on our skin. Signup and view all the answers

Why must animal defenses be flexible?

The defenses have to be flexible and able to defend against any threat irrespective of the nature of the causal microbe, as there is great diversity among disease-causing microbes. Signup and view all the answers

What molecules alert the animal body to a microbial threat?

Molecules from the commensal bacteria cross the intestinal wall, enter the body, and influence our immune system. Signup and view all the answers

Flashcards

Microbial Dominance

Microbes, including bacteria and viruses, are ubiquitous and can be harmful, invading the body and causing damage.

Microbial Attraction

Animal tissues provide warmth, moisture, and nutrients, attracting microbes that attempt to invade and exploit these resources.

Commensal Microbiota

These are bacteria (and some viruses) that live on/in animals, without causing damage and share resources with the host.

Immune Tolerance

The immune system must tolerate or ignore commensal microbiota to maintain health, avoiding aggressive responses unless necessary.

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Regulated Immune Response

The defensive immune responses must be carefully regulated and must not be triggered unless necessary for the defense of the body.

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Bacterial Molecule influence

These microbial molecules can cross the intestinal wall, enter the body, and influence our immune system.

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Study Notes

Microbes, including bacteria and viruses, are abundant in our environment and bodies
Some microbes invade the body, multiply, exploit resources, and damage cells, causing sickness and death
Strong immune defenses are essential for animals to survive microbial invasions

Animal Attractiveness to Microbes

Animal tissues are warm, moist, and nutrient-rich, making them attractive to microorganisms
Dead bodies decompose rapidly as bacteria invade tissues

Microbes as Enemies and Commensals

Historically, all microbes were considered potential enemies, including bacteria, viruses, fungi, protozoa, and parasitic worms
Many bacteria and some viruses live on our bodies, especially in the intestines, airways, and skin, without causing damage
These bacteria, our normal microbiota, share resources with us and are considered commensal organisms

Tolerance of Commensal Microbiota

The presence of commensal microbiota on our surfaces must be tolerated or ignored for animals to remain healthy
Immune responses must be regulated and only triggered when necessary for defense
The immune system is aware of the intestinal microbiota, and bacterial molecules can cross the intestinal wall and influence our immune system
Defensive responses are measured, proportional, and controlled
Microbiota are needed for proper digestion and keep our defenses in peak operating condition