1 DD Bacterial Structure, Function and Growth

Question 1

List structural features of bacteria

Answer 1

1. Capsules
   
   2. Pili aka Fimbriae
   3. Rigid external cell wall
      
      • Peptidoglycans
   4. Cytoskeletal elements
   5. Cytoplasmic membrane
   6. Flagella

Question 2

Capsule:

• describe
• purpose
• Why do we even care?(How do we take advantage of it?)

Answer 2

a. Outer complex polysaccharide layer→ Gelatinous and loose as a goose
b. Purpose: protects against phagocytosis → “enhance virulence”
c. Most capsular polysaccharides are antigenic →used as components of vaccines to prevent bacterial infections

Question 3

Pili “fimbriae”

• describe
• purpose
• Why do we even care?(How do we take advantage of it?)

Answer 3

a. Long, slender, antigenic hair-like glycoproteins on surface

b. Function: bacterial adherence
i. Some (few) bacteria: sex pili → bacterial conjugation

c. Can make antibodies against pili → block bacterial adherence → resist bacterial infection

Question 4

Peptidoglycans

• describe
• purpose
• Why do we even care?(How do we take advantage of it?)

Answer 4

a. Rigid polymer of repeating NAM and NAG. Makes up external cell wall

b. Purpose:
i. Structure and strength for cell wall (not shape)

c. Peptidoglycans are unique to bacteria- → great target for antibiotics.

Question 5

Rigid external cell wall

• describe
• purpose

Answer 5

a. Made of peptidoglycan in Gram (+)
Made of peptidoglycan and outer membrane in Gram (-)

b. Purpose: Cell shape + resisting osmotic lysis

Question 6

Describe differences in Peptidoglycan content in gram (+) vs gram (-) bacteria

Answer 6

Gram (+) bacteria: greater extent of peptidoglycan cross-linking
**Gram Positive: think P for Puffier Peptidoglycan

Gram (-) bacteria: lesser extent of peptidoglycan cross-linking
** Gram Negative: think N for Not as much peptidoglycan

Question 7

What is another name for the two hexose, NAG and NAM?

Answer 7

N-acetylglucosamine (GlcNAc or NAG)

N-acetylmuramic acid (MurNAc aka NAM)

Question 8

Intracellular cytoskeletal elements

• purpose
• describe its components

Answer 8

a. Purpose: Determines cell shape

b. Bacteria tubulin: FtsZ
c. Bacteria actin: MreB and ParM
d. Bacteria Intermediate filament protein: CreS (crescentin)

Question 9

Cytoplasmic membrane

- describe

Answer 9

Lipid bilayer of phospholipids and lots of proteins (60-70%)

• Anatomical physiological barrier between inside and outside of cell

Question 10

List different functions of cytoplasmic membrane (6)

Answer 10

i. Selective permeability
ii. Electron transport
Iii. Transport of metabolites
iv. Biosynthesis of lipids and cell envelope components
v. DNA replication
vi. Flagellar rotation

Question 11

Flagella

• purpose
• types of movement

Answer 11

Function: motility → used to move bacteria during chemotaxis

i. Counter-clockwise: swimming (unidirectional)
ii. Clockwise: tumbling  (ie clumsily changing direction)

Question 12

Types of Flagella

Answer 12

i. Polar: 1 or several flagella at 1 end

ii. Peritrichous: flagella distributed over surface

Question 13

Whats another name for cytoplasmic membrane? In which Gram type of bacteria would you use this name?

Answer 13

Inner membrane in Gram (-) bacteria

• note: gram (-) bacteria also have an outer membrane
• gram + bac have no outer membrane - only 1 general plasma membrane

Question 14

Whats another name for Pili?

Answer 14

Fimbriae

Question 15

Why do we care about flagella?

example

Answer 15

Most are antigenic → can be used for classification

1) Ie: H antigens of enteric bacteria

Question 16

List bacterial structures that are antigenic

Answer 16

capsules
pili
Flagella

Question 17

Nucleoid

Answer 17

aka nuclear body - where DNA is located in bacteria

Question 18

Whats the difference between bacteria chromosome and plasmid?
- give an example of a plasmid

Answer 18

i. Chromosome: a single, double-stranded, circular DNA molecule

ii. Plasmid: smaller, extra-chromosomal, self replicating DNA molecules → code for virulence factors
1) Ie: R factors: plasmids that carry genes that determine resistance to antibiotics

Question 19

Describe layers of Gram (+) bacteria

Answer 19

2 layers total:
- 1 layer of cell wall:
□ Thick, extensively linked peptidoglycan layer containing teichoic acids
- 1 plasma membrane layer

Lipotechoic acid underneath cytoplasmic membrane

Question 20

Lipoteichoic acid:

Answer 20

found attached to underlying cytoplasmic membrane of gram + bacteria → anchor cell wall (peptidoglycan) to membrane

• only found in gram +

Question 21

Teichoic acid

Answer 21

Repeating bacterial polysaccharides (polyglycerol-P aka Polyribitol-P backbone) → extends peptidoglycan surface

-only found in gram +

Question 22

Describe layers of Gram (-) bacteria

Answer 22

3 layers total:
	 2 layers of cell wall:
		□ Outer membrane
		□ Thin, sparsely linked peptidoglycan layer
	 1Plasma membrane

Question 23

Function of outer membrane of Gram (-) bacteria

Answer 23

□ Barrier against antibiotic entry

□ Protection against detergents and toxic compounds

Question 24

Components of outer membrane of Gram (-) bacteria

Answer 24

lipopolysaccharide (LPS), lipoproteins, and porins

Question 25

lipopolysaccharide (LPS)

Answer 25

polysaccharide containing 1. Lipid A 2. Core polysaccaride 3. O side chain oligosaccharides

Question 26

Lipid A and O side chain oligosaccharides | -Where are they found and What are they:

Answer 26

Found in LPS of outer membrane of Gram - bacteria Lipid A - the toxic component of endotoxin O side chain oligosaccharides - function as somatic antigens aka O antigen

Question 27

Phases of bacterial growth curve

Answer 27

1. lag phase 2. exponential(logarithmic) phase 3. Stationary phase 4. Death phase

Question 28

Based on classifications of energy sources, the majority of bacteria are?

Answer 28

Heterotrophic - requires organic carbon

Question 29

autotrophic organisms

Answer 29

obtain carbon exclusively from CO2

Question 30

Fastidious organisms

Answer 30

requires carbon and essential growth factors (aa, vitamins, purines, pyrimidines, inorganic ions) -Deficient in 1/more biosynthetic pathways → requires rich growth media

Question 31

Facultative anaerobe

Answer 31

respires w/ low O2 | ferments in absence of O2

Question 32

What type of bacteria grows best at low O2 [ ], AND | can grow without O2?

Answer 32

microaerophilic

Question 33

Which energy currency is used for flagellar rotation?

Answer 33

Proton motive force (PMF)

Question 34

Fermentation

Answer 34

catabolic process in which organic compounds serve as both e- donor and acceptor

Question 35

Do heterotrophic bacteria use fermentation or respiration to generate energy and reducing power?

Answer 35

Both

Question 36

List antimicrobial agent targets

Answer 36

1. Cell wall 2. Outer and cytoplasmic membrane 3. Protein synthesis at ribosome levels 4. Nucleic acid synthesis. 5. Metabolism

Question 37

What bacterial structures are unique to gram + bacteria?

Answer 37

lipoteichoic acid

Question 38

What bacterial structures are unique to gram - bacteria?

Answer 38

``` porins LPS endotoxin periplasmic space (beta lactamase location) ```

Question 39

Name for Bacteria tubulin

Answer 39

FtsZ

Question 40

Name for Bacteria actin

Answer 40

MreB and ParM

Question 41

Name for Bacteria Intermediate filament protein

Answer 41

CreS (crescentin)