1 DD Bacterial Structure, Function and Growth Flashcards Preview

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Flashcards in 1 DD Bacterial Structure, Function and Growth Deck (41)
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List structural features of bacteria

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


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

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


Pili "fimbriae"
- describe
- purpose
- Why do we even care?(How do we take advantage of it?)

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


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

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.


Rigid external cell wall
- describe
- purpose

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

b. Purpose: Cell shape + resisting osmotic lysis


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

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


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

N-acetylglucosamine (GlcNAc or NAG)

N-acetylmuramic acid (MurNAc aka NAM)


Intracellular cytoskeletal elements
- purpose
-describe its components

a. Purpose: Determines cell shape

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


Cytoplasmic membrane
- describe

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

- Anatomical physiological barrier between inside and outside of cell


List different functions of cytoplasmic membrane (6)

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


- purpose
-types of movement

Function: motility → used to move bacteria during chemotaxis
i. Counter-clockwise: swimming (unidirectional)
ii. Clockwise: tumbling (ie clumsily changing direction)


Types of Flagella

i. Polar: 1 or several flagella at 1 end
ii. Peritrichous: flagella distributed over surface


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

Inner membrane in Gram (-) bacteria

*note: gram (-) bacteria also have an outer membrane

*gram + bac have no outer membrane - only 1 general plasma membrane


Whats another name for Pili?



Why do we care about flagella?

Most are antigenic → can be used for classification
1) Ie: H antigens of enteric bacteria


List bacterial structures that are antigenic




aka nuclear body - where DNA is located in bacteria


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

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


Describe layers of Gram (+) bacteria

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


Lipoteichoic acid:

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

- only found in gram +


Teichoic acid

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

-only found in gram +


Describe layers of Gram (-) bacteria

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


Function of outer membrane of Gram (-) bacteria

□ Barrier against antibiotic entry
□ Protection against detergents and toxic compounds


Components of outer membrane of Gram (-) bacteria

lipopolysaccharide (LPS), lipoproteins, and porins


lipopolysaccharide (LPS)

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


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

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


Phases of bacterial growth curve

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


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

Heterotrophic - requires organic carbon


autotrophic organisms

obtain carbon exclusively from CO2


Fastidious organisms

requires carbon and essential growth factors (aa, vitamins, purines, pyrimidines, inorganic ions)

-Deficient in 1/more biosynthetic pathways → requires rich growth media