MicroBio Chapter 3 study questions

What are the three basic bacterial shapes? Provide an example of each.

• Coccus: Round

• Bacillus: Rod-shaped

• Curved/spiral: Includes vibrio (comma-shaped), spirillum (short chains), and spirochete (corkscrew, usually single cells)

Define the term "pleomorphic" and explain how it relates to bacterial shape.

• Refers to bacteria that can have variations in cell shape and structure.

Describe the different arrangements of cocci and bacilli. What do terms like "strepto-" and "diplo-" indicate?

• Cocci:

  • Streptococci = chains

  • Diplococci = pairs

• Bacilli:

  • Single, diplobacilli, streptobacilli, palisades (side-by-side)

Differentiate between spirillum and spirochete in terms of shape and cellular arrangement.

• Spirillum: Spiral-shaped and often in short chains

• Spirochete: Spiral-shaped, usually single cells, with corkscrew motion

What is a vibrio, and how does it differ from a typical rod-shaped bacterium?

• Vibrio: Comma-shaped or bent rod

• Rod-shaped (bacillus): Straight cylindrical cells

What is the function of bacterial flagella, and what are the five major flagellar arrangements?

• Function: Motility via rotation

• Arrangements:

  • Monotrichous: One flagellum

  • Lophotrichous: Tufts from same site

  • Amphitrichous: One at each pole

  • Peritrichous: All over the surface

  • Atrichous: No flagella

What are fimbriae, and how do they assist bacteria?

Hair-like projections used for attachment to surfaces or other cells

How do pili contribute to bacterial reproduction or genetic exchange?

Hollow protein tubes used for conjugation (DNA transfer); found on some gram-negative bacteria

What is the role of nanotubes in bacterial cells?

• Cytoplasmic extensions that adjoin adjacent cells for nutrient/energy exchange

Compare the slime layer and capsule forms of the glycocalyx in terms of structure and function

• Slime layer: Loose glycocalyx shield

• Capsule: Dense, thick glycocalyx

• Function: Attachment and protection from phagocytes and water loss

Which appendage is unique to spirochetes and allows them to move in a corkscrew motion?

• Axial filament (periplasmic flagella)

What cellular processes take place at the cytoplasmic membrane in bacteria?

• Site for energy reactions, nutrient processing, synthesis

• Selectively permeable barrier

Describe the composition and role of the bacterial ribosome. What are its subunits?

• Site of protein synthesis

• Made of rRNA and proteins

• Subunits: 50S (top) + 30S (bottom) = 70S ribosome

Where is bacterial DNA located in the cell, and what is the function of plasmids?

• DNA is in the nucleoid (dense region)

• Plasmids: Nonessential DNA that can confer traits like drug resistance and toxin/enzyme production

What are the key differences between gram-positive and gram-negative cell walls?

• Gram-positive: Thick peptidoglycan, teichoic acids

• Gram-negative: Thin peptidoglycan, outer membrane with LPS, porins

Why are gram-negative bacteria more susceptible to lysis despite having an outer membrane?

Their thin peptidoglycan layer provides less structural strength

What role do teichoic and lipoteichoic acids play in the gram-positive cell wall?

Found in gram-positive walls; help with wall maintenance and enlargement and contribute to acidic charge

What clinical challenges are associated with the lipopolysaccharide (LPS) layer in gram-negative bacteria?

Contributes to virulence; can trigger immune responses or septic shock

What is the main function of the bacterial cell wall regardless of type?

• Determine cell shape and provide structural strength

What features distinguish the cell walls of archaea from those of bacteria and eukaryotes?

Made of polysaccharides or proteins, but lack peptidoglycan

What makes acid-fast bacteria like Mycobacteria different from typical gram-positive organisms?

• Modified gram-positive structure

• Mycobacteria contain mycolic acid

How do Mycoplasma bacteria survive without a cell wall, and what disease can they cause?

• No cell wall; membranes fortified with sterols

• Cause walking pneumonia (Mycoplasma pneumoniae)

What are L-form bacteria, and why are they significant in persistent infections?

Lose their wall during part of their life cycle; may be involved in persistent infections

What triggers the formation of endospores in bacteria?

Harsh/unfavorable environmental conditions

Name at least three diseases caused by endospore-forming bacteria.

tetanus, Botulism, Anthrax (typically Clostridium and Bacillus genera)

Why are endospores so difficult to destroy? List at least four conditions they can withstand.

Resist extreme heat, drying, freezing, radiation, and chemicals

What is the difference between a vegetative cell and an endospore?

• Vegetative: Active, growing

• Endospore: Dormant, formed during stress

What is the medical significance of endospore formation in certain bacteria?

Most are harmless, but some form highly resilient pathogens that are hard to eliminate and cause disease

How are archaea more closely related to eukaryotes than bacteria, despite being prokaryotic?

Share rRNA sequences, ribosome structure, and protein synthesis characteristics

Describe three environmental conditions where archaea can thrive and name the term used for such organisms.

Extremely hot, salty, or acidic conditions extremophiles

Do archaea live in the human body, and if so, what might their presence indicate about microbial diversity?

Yes, especially in places like the gut, mouth, and skin. Their presence shows that the human microbiome is more diverse than just bacteria and includes different types of microbes.

Bacterial cells can have a protective polysaccharide coating termed the _____, that is called either a capsule or slime layer based on its structure.

glycocalyx

An appendage which forms a channel for the exchange of genetic material during bacterial conjugation is called a

pilus

Nanotubes or nanowires are long extensions of the ______ that bacteria use as channels to transfer nutrients or electrons.

cytoplasmic membrane

Special membrane channels located in the outer membrane of gram-negative cells are called

porins

The group of bacteria that naturally have no cell wall, but have a cytoplasmic membrane that is stabilized by sterols, is called

mycoplasma

Which term is used to describe the phospholipid barrier surrounding the peptidoglycan layer in gram-negative bacteria?

outer membrane

Bacteria that are spatially close to one another may be able to communicate via

chemicals and nanowires

A ______ is a hollow, protein tube that facilitates the transfer of genetic material between bacterial cells.

pilus

The lipid portion of lipopolysaccharide is known as endotoxin because it can cause

fever and shock

Water serves as a solvent for the contents of the cell, making up 70-80% of the internal gelatinous solution known as the

cytoplasm

Bacterial endospores are heat resistant because

calcium dipicolinate dehydrates the endospore

Very thin, long, tubular extensions of the cytoplasmic membrane that bacteria use as channels to transfer amino aicds or electrons are called

nanotubes

Small proteinaceous appendages in gram-negative bacteria that function in DNA exchange are called conjugation

pili

The lipid portion of lipopolysaccharide (LPS) is also known as

endotoxin

The high content of calcium and dipicolinic acid in bacterial endospores confers ______ resistance on them.

heat

What are porins?

protein channels that span the outer membrane

The protective covering called the ______ develops as a coating of repeating polysaccharide or glycoprotein units.

glycocalyx