Chapter 26- Prokaryotes Bacteria and Archaea

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Where are prokaryotes found?

Everywhere- including extreme environments (acidic, salty, cold, hot) and deep underground two miles below earth’s surface.

Are prokaryotes unicellular or multicellular?

Mostly unicellular (some colonial/simple multicellular species exist).

What type of DNA do prokaryotes have and where is it located?

Circular DNA, located in a nucleoid region (no nucleus).

What are plasmids?

Small, extra pieces of DNA found in prokaryotes that may carry beneficial genes, like antibiotic resistance.

How do prokaryotes reproduce?

Asexually by binary fission

Which domains include prokaryotes?

Bacteria and Archaea.

Which domain includes eukaryotes?

Eukarya (protists, animals, fungi, plants).

Differences in DNA structure between prokaryotes and eukaryotes?

Prokaryotes have circular DNA; eukaryotes have linear chromosomes.

Do prokaryotes have membrane-bound organelles?

No.

What are some differences between Bacteria and Archaea?

• Cell walls: Bacteria have peptidoglycan; Archaea do not.

• Archaea often live in extreme environments (extremophiles).

• Histones: Present in Archaea, absent in Bacteria.

What are the 6 metabolic types in prokaryotes (based on energy and carbon source)?

1. Photoautotroph

2. Chemoorganoheterotroph (organoheterotroph)

3. Photoheterotroph

4. Organoautotroph

5. Lithoautotroph

6. Lithoheterotroph

Which four metabolic types are exclusive to prokaryotes?

Photoheterotroph, Organoautotroph, Lithoautotroph, Lithoheterotroph

What metabolic types can eukaryotes perform?

Only photoautotroph and organoheterotrophs.

How old are prokaryotes?

3.5 to 3.8 billion years old — Earth’s first inhabitants.

What are the four types of oxygen metabolisms in prokaryotes?

1. Obligate aerobes – require O₂

2. Obligate anaerobes – poisoned by O₂

3. Facultative anaerobes – can use O₂ or not

4. Aerotolerant anaerobes – don’t use O₂ but not harmed by it

What limits prokaryote reproduction?

• Nutrient depletion

• Toxic waste accumulation

• Competition

• Predation

How do prokaryotes increase genetic diversity?

• Transformation: Uptake of DNA from the environment

• Transduction: Virus transfers DNA

• Conjugation: DNA transferred between cells via direct contact

What are the 4 main shapes of prokaryotes?

• Cocci (spheres)

• Bacilli (rods)

• Vibrio (comma-shaped)

• Spirilla (spirals)

What allows prokaryotic movement?

Flagella (longer)

Cilia (shorter)

What are endospores?

Tough, resistant structures that help some prokaryotes survive harsh conditions.

What do bacterial cell walls contain?

Peptidoglycan.

Difference between Gram+ and Gram- bacteria?

• Gram+ = thick peptidoglycan, susceptible to penicillin

• Gram- = thin peptidoglycan, resistant to penicillin

What is mutualism?

A (+/+) interaction where both species benefit.

What is parasitism?

A (+/–) interaction where one benefits and the other is harmed.

What is a microbiome?

A community of prokaryotes (mostly bacteria) living on/in organisms, especially humans.

Functions of the human microbiome?

• Digestion

• Vitamin production

• Mood regulation

• Immune health

What are pathogenic bacteria?

Bacteria that cause disease (very few species).

What is virulence?

The strength of an infection; a heritable trait.

Who discovered the germ theory?

John Snow (cholera mapping), Louis Pasteur refined it.

What is the hygiene hypothesis?

Overuse of antibiotics and hygiene reduces microbiome diversity, possibly increasing autoimmune diseases.

What do antibiotics target?

Traits like cell wall formation not specific species.

How does antibiotic resistance arise and spread?

Through mutations and spread via conjugation and survival advantages.

How can we slow antibiotic resistance?

• Reduce use in farm animals

• Don’t share prescriptions

• Avoid antibiotic-laced products

• Follow doctor’s instructions

Why is recombination important for prokaryotes?

It increases genetic diversity, environmental adaptability, and evolutionary potential.