Ecology Paper 7 Flashcards

What did biologists originally believe about the human body?

That it was a self-sufficient physiological island controlling all internal processes.

What is the modern view of the human body?

A complex ecosystem with trillions of microorganisms.

What is the microbiome?

All microbial cells and their genes living in and on the body.

Where are microbes mainly found?

Skin, mouth, genital areas, and especially intestines.

How do bacterial cells compare to human cells in number?

About 10 times more bacterial cells than human cells.

Do microbes help or harm us overall?

Most are beneficial and essential.

What processes do microbes assist with?

Digestion, growth, and immune defense.

Why were microbes once viewed negatively?

Focus was mainly on pathogens.

What are commensals?

Beneficial microbes that live with us.

Are humans born with microbes?

No, newborns are sterile.

How do babies acquire microbes?

Birth canal, breastfeeding, contact, and environment.

Why is studying gut microbes difficult?

Many cannot survive in oxygen.

How do scientists study microbes today?

By analyzing DNA and RNA.

What gene is used to identify bacteria?

16S rRNA gene.

What does sequencing this gene reveal?

Which species are present.

How many microbial genes are in the gut?

About 3.3 million.

How many genes are in the human genome?

About 20,000-25,000.

Do all people have the same microbiome?

No, each is unique.

Do identical twins share microbiomes?

No, they differ.

How similar is human DNA across people?

About 99.9% identical.

What explains differences between people beyond DNA?

Microbiome variation.

Can beneficial bacteria become harmful?

Yes, if they enter the wrong place.

What is sepsis?

Bacteria in the bloodstream causing infection.

What is peritonitis?

Infection of abdominal tissues.

What vitamins do microbes help produce?

Vitamin B and others.

Why is vitamin B important?

Energy, DNA synthesis, fatty acids.

What is a key digestive role of microbes?

Breaking down indigestible food.

What does Bacteroides thetaiotaomicron do?

Breaks down complex plant carbohydrates.

Why is it important?

Humans lack enzymes for these carbs.

What does it produce?

Simple sugars and short-chain fatty acids.

What benefit do these products provide?

Energy for the host.

What happens without gut microbes?

More calories are needed to maintain weight.

What is Helicobacter pylori?

A stomach bacterium.

What was it first known for?

Causing ulcers.

How are ulcers treated?

With antibiotics.

What beneficial role does H. pylori have?

Regulates stomach acid.

What gene affects this regulation?

cagA.

What hormones control appetite?

Ghrelin and leptin.

What does ghrelin do?

Stimulates hunger.

What does leptin do?

Signals fullness.

How does H. pylori affect ghrelin?

Reduces it after meals.

What happens when H. pylori is removed?

Hunger may increase.

What trend has occurred with H. pylori?

It has declined in populations.

What might this contribute to?

Obesity.

How can microbiomes affect body composition?

Influence stem cells into fat, muscle, or bone.

What is the effect of antibiotics on microbes?

They kill beneficial bacteria.

How can early antibiotic use affect children?

Increase obesity risk.

What lifestyle changes affect microbiomes?

C-sections, smaller families, cleaner environments.

How do C-sections affect microbes?

Reduce exposure to maternal bacteria.

Why do smaller families matter?

Less microbial transfer between siblings.

What is happening to microbiome diversity?

It is decreasing.

What are T cells?

Immune cells that attack pathogens.

What do regulatory T cells do?

Control and suppress immune responses.

Why are regulatory T cells important?

Prevent damage to body tissues.

What happens if immune balance is lost?

Autoimmune disease can occur.

How do microbes influence immunity?

They help regulate immune balance.

What is Bacteroides fragilis?

A bacterium that supports immune regulation.

What molecule does it produce?

Polysaccharide A (PSA).

What does PSA do?$Stimulates regulatory T cells.

What effect does PSA have?

Reduces inflammation.

What happens without PSA?

Immune dysfunction and inflammation.

What disease can result from imbalance?

Colitis.

What is mutualism?

Both organisms benefit.

What is happening to beneficial microbes today?

They are declining.

What diseases may increase as a result?

Autoimmune diseases.

What are examples of these diseases?

Crohn's, type 1 diabetes, multiple sclerosis.

Are microbiome-disease links proven?

Mostly correlations so far.

What is the goal of future research?

Prove cause-and-effect mechanisms.

What is the key takeaway?

Humans depend on microbes for health.