Ch 16 Microbial Life: Prokaryotes

What are prokaryotes?

Single-celled organisms without a nucleus or membrane-bound organelles.

What are the two domains of prokaryotes?

Bacteria and Archaea

What’s the difference between Gram-positive and Gram-negative bacteria?

• Gram-positive: thick peptidoglycan wall, stains purple

• Gram-negative: thin wall + outer membrane, stains pink, more antibiotic resistant

What is the function of a capsule in bacteria?

Protects the cell and helps it adhere to surfaces or other cells.

What structure allows bacteria to move?

Flagella

What is the role of pili in bacteria?

Attach to surfaces or transfer DNA during conjugation.

What is a plasmid?

Small circular DNA that carries extra genes (like antibiotic resistance).

What is binary fission?

Asexual reproduction where one cell splits into two identical cells.

What is conjugation in bacteria?

DNA transfer between bacteria via a sex pilus.

What are endospores?

Dormant structures that allow bacteria to survive harsh conditions.

What is a chemoheterotroph?

Organism that gets energy and carbon from organic molecules.

What is a photoautotroph?

Organism that uses sunlight and CO₂ to make food (e.g., cyanobacteria).

What are three major roles of bacteria in ecosystems?

Decomposition, nitrogen fixation, and bioremediation.

What is bioremediation?

Using bacteria to clean up environmental pollutants.

What are exotoxins and endotoxins?

• Exotoxins: secreted toxins from live bacteria

• Endotoxins: released from Gram-negative bacteria when they die

What makes Archaea different from Bacteria?

Archaea have no peptidoglycan and live in extreme environments.

What are the three main shapes of bacteria?

Cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped)

What structure helps bacteria move?

Flagella

What is the function of the capsule in bacteria?

Protection and helps bacteria stick to surfaces or each other

How do bacteria reproduce?

Asexually through binary fission

What are plasmids and why are they important?

Small rings of DNA that carry extra genes, often for antibiotic resistance

What is conjugation?

The transfer of plasmids between bacteria through pili

Why are Gram-negative bacteria harder to treat?

Their outer membrane resists antibiotics

What are photoautotrophs?

Organisms that use sunlight and CO₂ to make food (e.g., cyanobacteria)

What are chemoheterotrophs?

Organisms that get energy and carbon from organic molecules

How do bacteria contribute to nutrient cycles?

Decomposition, nitrogen fixation, and recycling elements like carbon

What is bioremediation?

Using bacteria to clean up pollution (e.g., oil spills)

How can bacteria be beneficial to humans?

Aid in digestion, produce vitamins, clean waste, and fight harmful microbes

What is the nucleoid region in a prokaryotic cell?

The area where the single circular chromosome (DNA) is located.

What type of ribosomes do prokaryotes have?

Smaller ribosomes than eukaryotes; a common antibiotic target.

Why is genetic variation in bacteria important?

It allows bacteria to evolve quickly, especially in response to antibiotics.

How can bacteria acquire new genes besides mutation?

Through horizontal gene transfer: conjugation, transformation, and transduction.

What is transformation in bacteria?

Uptake of DNA fragments from the environment.

What is transduction in bacteria?

Gene transfer by viruses (bacteriophages).

What is a biofilm?

A surface-coating colony of prokaryotes that communicate and stick together.

Why are biofilms medically important?

They make infections harder to treat due to resistance and protection of bacteria inside the film.

What is the difference between mutualism and commensalism in bacteria?

• Mutualism: Both host and bacteria benefit

• Commensalism: Bacteria benefit; host is unaffected

How are prokaryotes involved in the nitrogen cycle?

They fix nitrogen gas (N₂) into ammonia (NH₃) that plants can use.

What domain includes methanogens, halophiles, and thermophiles?

Archaea

What are the five major supergroups of eukaryotes (including protists)?

• Excavata

• SAR

• Archaeplastida

• Unikonta

• Amoebozoa (sometimes grouped with Unikonta)

What does SAR stand for in the SAR supergroup?

Stramenopiles, Alveolates, Rhizarians

What are key features of Stramenopiles?

Hair-like flagella; many are photosynthetic

Name two important stramenopiles.

Diatoms (glass-like walls), Brown algae (e.g., kelp)

What are alveolates known for?

Membrane-bound sacs (alveoli) under the plasma membrane

Name examples of alveolates.

Dinoflagellates, ciliates (e.g., Paramecium), and apicomplexans (e.g., Plasmodium)

What distinguishes rhizarians?

Unicellular organism, live in water or soil

Name examples of rhizarians.

Foraminiferans and radiolarians

What are the five major bacterial groups often studied in biology?

• Proteobacteria

• Gram-positive bacteria

• Cyanobacteria

• Chlamydias

• Spirochetes

What are Proteobacteria?

Large group of Gram-negative bacteria (e.g., E. coli)

What are Gram-positive bacteria known for?

Thick peptidoglycan wall; include Streptococcus and Staphylococcus

What are Cyanobacteria?

Photosynthetic bacteria; first to release oxygen into Earth's atmosphere

What are Chlamydias?

Intracellular parasites; cause STDs, live inside eukaryotic cells

What are Spirochetes?

Spiral-shaped bacteria; some cause Lyme disease or syphilis