Bacterial Cell Structure/Function

Question 1

Describe a biofilm. What is its impact on infection and antibiotic resistance. How do they facilitate spread of infection within a patient?

Answer 1

• def: organized, multicellular bacterial communities enclosed within matrix
• fxn: adherence, controlled release of bacteria from matrix, alters growth kinetics, activates stress and defense responses
• patho: resistant to immune cells and antibiotics; can branch off by secreting enzymes and degrading matrix
• spread: sites of continuous dissemination of bacteria => reinfection

Question 2

Define pili. What are its functions? How does it contribute to pathogenesis?

Answer 2

• def: long, filamentous projections that cover the surface of some gram (-) bacteria
• promote attachment to host via specialized tips

Question 3

Define capsule. What are its function? How does it contribute to pathogenesis?

Answer 3

• def: thick, amorphous layer composed of polysaccharides, proteins, or DNA.
• only produced in virulent strains or under certain conditions (not required for life)
• Fxn: provides protection from host defenses, adherence, and can be toxic

Question 4

What are the components of the bacterial cell envelope?

Answer 4

• inner membrane
• cell wall
• outer membrane (for gram (-) only)

Question 5

Describe the inner membrane.

Answer 5

• found in both gram (+) and (-) bacteria
• composed of lipid bilayer of phospholipids and proteins
• selective transportation of molecules in and out of the cell

Question 6

Describe the cell wall.

Answer 6

• found in both gram (+) and (-) bacteria
  ==> (+) thick, multilayered, contains teichoic and lipoteichoic acids (antigenic determinants)
  ==> (-) thin layer
• composed of peptidoglycan (sugar chain with protein side chains)
  ==> allows meshwork to form
• unique to bacteria

pathogenesis/treatment
=> antibiotics can attack cell wall and cause lysis
=> cell wall can be toxic to host

Question 7

Describe the outer membrane.

Answer 7

• found only in gram (-)
• lipid bilayer with LPS (lipopolysaccharide) on the outer layer
• strong barrier to molecule entry into the cell
• contains porins for passive entry

Question 8

List components of the interior of bacterial cells.

Answer 8

• ribosomes: frequent antibiotic targets
• nucleoid
• plasmids: encode virulence factors (resistance, pili); easily transferred, especially due to overuse of antibiotics

Question 9

Define spores.

Answer 9

• dormant cell type formed by certain bacteria in response to stress
• highly resistant and easily dispersed
• can directly cause disease or after germination (conversion to normal cell) cause disease

Question 10

Define mycoplasma.

Answer 10

simple cell consisting only of inner membrane

• no peptidoglycan
• different shapes

Question 11

How do biofilms form?

Answer 11

• cells sense environment

- cell-cell communication via pheromones initiates matrix formation

Question 12

Describe strategies to defeat biofilms.

Answer 12

1. block pheromone communication
2. lack of cell-cell communication
3. biofilm cannot continue to form => exposed cells
4. attack bacteria

Question 13

Define periplasm.

Answer 13

between inner and outer membranes of gram negative bacteria

Question 14

Describe the process of spore formation.

Answer 14

1. NORMAL/VEGETATIVE CELL GROWTH
   - normal cell division
2. SPORULATION
   - spore made inside normal cell
   - released into the environment
   - inert, dormant, resistant, metabolically inactive
3. GERMINATION
   - typically due to starvation
   - sheds membrane and enters normal growth
   - metabolically active, has virulence factors

Question 15

Describe flagella.

Answer 15

• motility

- strong antigens (immunogenic)