External Structures

Question 1

function of components external to the cell wall

Answer 1

• attachment to surfaces
• protection
• horizontal gene transfer (sex pilus)
• movement

Question 2

list the polysaccharide layers

Answer 2

1. capsule
2. slime layer
3. glycocalyx

Question 3

describe the capsule (polysaccharide layer)

Answer 3

• well organized layer of polysaccharides, not easily removed
• protects against desiccation
• helps bacteria resist phagocytosis (complement proteins can’t bind to capsule, so macrophage can’t eat bacteria)

Question 4

describe the slime layer (polysaccharide layer)

Answer 4

less well organized layer of polysaccharide, diffuse and easily removed

Question 5

describe the glycocalyx (polysaccharide layer)

Answer 5

“sugar shell”, encompasses both capsule and slime layer together

Question 6

biofilms

Answer 6

• protected by and attached by layers of polysaccharide
• formed on teeth, rocks, other surfaces
• can form on medical devices-implants

Question 7

quorum sensing

Answer 7

the way that bacteria communicate with each other within a biofilm to change gene expression
- polysaccharide production goes up
- antibiotic resistance goes up
- flagella expression goes down

Question 8

sessile vs. planktonic

Answer 8

sessile: bacteria stay in biofilm
planktonic: bacteria escape biofilm and start to move about

Question 9

define biofilm

Answer 9

glycocalyx converges between cells

Question 10

describe some functions of polysaccharide layers

Answer 10

• may confer growth advantages
• help adhere to host
• help avoid phagocytosis/immune system
• protect against chemicals, detergents, bacteria viruses, etc.
• contains H2O to help avoid hydration

Question 11

describe the S layer of protein

Answer 11

• patterned like floor tiles
• helps give cell shape
• protects against changes in pH and osmotic pressure
• aids in virulence by promoting attachment and protection from other bacteria

Question 12

mycolic acid layer

Answer 12

• waxy outer layer in Mycobacterium
• stains poorly with gram stain
• acid fast, shows up hot pink
• innately antibiotic resistant: resistant to dehydration, antibiotics, and phagocytosis

Question 13

pili and fimbriae (interchangeable)

Answer 13

• small, short hair-like appendages
• not involved in motility, help adhere to host

Question 14

sex pilus

Answer 14

• medium hair-like appendage
• only in bacteria with plasmids carrying sex pili genes
• connect bacteria for transfer of genetic material (“mating”)

Question 15

flagella

Answer 15

• largest hair-like appendages
• function is motility

Question 16

monotrichous

Answer 16

1 flagellum

Question 17

amphitrichous

Answer 17

1 flagellum at each pole

Question 18

lophotrichous

Answer 18

tuft of flagella at one or both ends

Question 19

peritrichous

Answer 19

flagella evenly spread over whole bacteria

Question 20

structure of flagella

Answer 20

• hollow tube of protein called flagellin, which is comprised of the filament (long part), basal body (embedded in cell), and hook (links basal body and filament)

Question 21

chemotaxis

Answer 21

• bacteria moving towards food and away from toxins
• needs flagella and chemoreceptors