Chapter 3: Bacteria and Archaea

Chapter 3: Bacteria and Archaea

What are prokaryotes?

Organisms that do not contain a nucleus. They include the domains Bacteria and Archaea.

What are the two domains of prokaryotes?

Bacteria and Archaea.

What is the main difference between prokaryotes and eukaryotes?

Prokaryotes lack a nucleus, while eukaryotes contain a nucleus.

What domain contains eukaryotic organisms?

Eukarya.

What is the typical size of prokaryotic cells?

About 1–5 μm.

What is a coccus?

A round or spherical bacterial cell shape.

What is a bacillus?

A rod-shaped or oblong bacterial cell shape.

What is a Vibrio?

A curved, comma-shaped bacterial cell.

What are spirilla and spirochetes?

Spiral-shaped bacterial cells.

What are monomorphic bacteria?

Bacteria that exist as one consistent shape.

What are pleomorphic bacteria?

Bacteria that vary in shape and size and do not have a defined shape.

What does diplo- mean?

Two bacterial cells together.

What does strepto- mean?

A chain of bacterial cells.

What is a tetrad arrangement?

Four bacterial cells arranged together.

What is a sarcinae arrangement?

Eight bacterial cells arranged in a cube.

What does staphylo- mean?

A cluster or bunch of bacterial cells.

How do bacteria reproduce?

Bacteria reproduce asexually through binary fission.

What is binary fission?

A process where one bacterial cell divides into two genetically identical daughter cells.

What is the first step of binary fission?

The bacterial DNA is replicated.

What happens after DNA replication in binary fission?

The cytoplasm increases and the two copies of DNA separate.

What happens when the membrane begins to pinch inward during binary fission?

A septum/cross-wall begins forming between the two cells.

What is the final step of binary fission?

Two daughter cells separate.

Is binary fission sexual or asexual reproduction?

Asexual reproduction.

What are the three major layers studied in bacterial structure?

External structures, cell envelope (walls and membranes), and internal structures.

What is an S-layer?

A thin protein layer outside the cell wall made of thousands of repeated proteins.

What is the function of the S-layer?

It provides protection and acts like armor in hostile environments.

What is a glycocalyx?

A sugar coating outside bacteria made of polysaccharides and glycoproteins.

What are the two types of glycocalyx?

Capsule and slime layer.

What is a capsule?

A tightly packed glycocalyx layer attached to the bacterial surface.

What is the function of a capsule?

Protection, attachment, and helping bacteria avoid immune defenses.

What is a slime layer?

A loosely packed glycocalyx layer that protects bacteria from dehydration.

Why is glycocalyx important medically?

It helps bacteria attach to surfaces and form biofilms.

What are biofilms?

Communities of bacteria attached to surfaces and protected by a glycocalyx.

What are fimbriae?

Short, sticky protein projections used for bacterial attachment.

What is the function of fimbriae?

Helping bacteria attach to surfaces and host cells and form biofilms.

What are pili?

Longer hollow protein tubes are used for attachment and DNA transfer.

What is motility?

The ability of an organism to move through its environment.

What are flagella?

Protein structures used by bacteria for movement.

What is chemotaxis?

Movement in response to a chemical stimulus.

What is positive chemotaxis?

Movement toward a chemical signal.

What is negative chemotaxis?

Movement away from a chemical signal.

What are the three parts of a bacterial flagellum?

Basal body, hook, and filament.

What is the basal body of a flagellum?

The structure that anchors the flagellum and controls movement.

What is the hook of a flagellum?

The connector between the basal body and filament.

What is the filament of a flagellum?

The long protein structure that rotates and pushes the cell.

What happens when a flagellum rotates counterclockwise?

The bacterium performs a run and moves quickly in one direction.

What happens when a flagellum rotates clockwise?

The bacterium tumbles and changes direction randomly.

What is a monotrichous flagellar arrangement?

One flagellum is located at one end of the cell.

What is a lophotrichous flagellar arrangement?

A tuft of flagella located at one end of the cell.

What is amphitrichous flagellar arrangement?

Flagella located at both ends of the cell.

What is a peritrichous flagellar arrangement?

Flagella covering the entire surface of the cell.

What is the bacterial cell membrane made of?

A phospholipid bilayer containing proteins.

What are the functions of the bacterial cell membrane?

Transport, environmental sensing, and communication.

What is the function of the bacterial cell wall?

Provides structure, prevents lysis, protects from osmotic pressure, and helps attachment.

What is peptidoglycan?

A molecule made of sugars and peptides that forms bacterial cell walls.

What defines Gram-positive bacteria?

A thick peptidoglycan cell wall and one membrane.

What defines Gram-negative bacteria?

A thin peptidoglycan layer and two membranes.

Why do Gram-positive bacteria stain purple?

Their thick peptidoglycan traps crystal violet dye.

Why do Gram-negative bacteria stain pink?

Their thin cell wall loses crystal violet and absorbs the pink counterstain.

What is unique about Gram-positive cell walls?

They contain teichoic acid and lipoteichoic acid.

What is unique about Gram-negative bacteria?

They contain an outer membrane with lipopolysaccharide (LPS).

What is the periplasm?

The space between the inner and outer membranes of Gram-negative bacteria.

What is LPS?

Lipopolysaccharide found in the Gram-negative outer membrane.

Why is LPS clinically important?

It can trigger a strong immune response because it is recognized as foreign.

What is the cytoplasm?

The internal fluid of the bacterial cell containing cellular structures.

What is the nucleoid?

The region where bacterial DNA is located.

Do bacteria have a nucleus?

No.

What is a bacterial chromosome?

A circular DNA molecule containing essential genes.

What are plasmids?

Small circular DNA molecules containing additional genes.

What is the function of ribosomes?

Protein synthesis.

What type of ribosome do bacteria have?

70S ribosomes made of 50S and 30S subunits.

What are inclusion bodies?

Storage structures used to store nutrients, gases, or minerals.

What is an endospore?

A durable, inactive survival structure produced by some bacteria.

Are endospores used for reproduction?

No, they are used only for survival.

What conditions can endospores survive?

Heat, radiation, dehydration, starvation, and chemicals.

What is germination?

The process where an endospore returns to an active bacterial cell.

What similarities do Bacteria and Archaea share?

Both are prokaryotes, lack nuclei, have circular DNA, and contain 70S ribosomes.

What makes Archaea different from Bacteria?

Archaea lack peptidoglycan, have different membranes, and have eukaryote-like protein synthesis.

Do Archaea have peptidoglycan cell walls?

No.

What type of membrane lipids do Archaea have?

Branched fatty acids.

What structure do Archaea use instead of bacterial flagella?

Archaella.

What is a hamus?

A grappling-hook-like structure used by Archaea for attachment.

Who discovered that Archaea should be a separate domain?

Carl Woese.

What evidence did Carl Woese use to separate Archaea from Bacteria?

Ribosomal RNA (rRNA) sequencing.

What are the three domains of life?

Bacteria, Archaea, and Eukarya.

Why are Archaea considered their own domain?

They have unique genetic, membrane, and cellular characteristics different from those of bacteria.