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Flashcards in Bacteria and Archaea Deck (52)
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1

What are the possible shapes of bacteria?

coccus, rod, spirillum, spirochete, budding/appendaged, filamentous

2

What is the purpose of cell walls?

allow bacteria to withstand intracellular osmotic pressure, responsible for shape and rigidity

3

What are the steps of a Gram's stain?

1. flood heat fixed smear with crystal violet for 1 min (all cells purple)
2. add iodine solution for 1 min (all cells purple)
3. decolonize with alcohol for ~20s (Gram positive=purple, Gram negative=clear)
4. counterstain with safranin for 1-2 min (Gram positive = purple, Gran negative = red/pink)

4

Why is the colour different in Gram positive and negative cells?

Gram positive and negative both have a peptidoglycan layer but Gram negative also have an outer membrane which is the reason for the colour difference

5

What is peptidoglycan?

polymer of peptidoglycan with many known variations

6

What is another name for peptidoglycan?

meurin

7

What are the subunits of peptidoglycan?

NAG and NAM (sugars), short peptide chains containing D amino acids, NAM and DAP (never found in eukaryotes or archaea)

8

What is the backbone of peptidoglycan made up of?

polymerized sugars (NAM and NAG)

9

What is lysozyme?

secreted in tears/saliva/other bodily fluids, protects the body against pathogens, works to hydrolyze the bonds in the peptidoglycan sugar backbone

10

What provides rigidity in peptidoglycan?

In one direction it is provided by the polymerization, in the other it is provided by bonds between adjacent peptides on adjacent peptidoglycan

11

Gram negative have ___ cross linking while Gram positive have ___ cross linking

direct/interbridge

12

what is another name for cross linking?

transpeptidation

13

Describe the characteristics of the Gram positive cell wall

- up to 90% peptidoglycan
- teicholic acid and lipoteicholic acid (composed of glycerol-P or ribitol-P) combined with a.a. and sugar covalently bonded to the peptidoglycan

14

What is sortase?

the enzyme that covalently attaches wall associated PRO to the peptidoglycan

15

Describe the characteristics of the Gram negative cell wall

- 5-10% peptidoglycan

16

What is the periplasm?

space between cytoplasmic and outer membrane, contains peptidoglycan and a high quantity of PRO with specific functions

17

What is another name for the periplasm?

PRO gel

18

What is the outer membrane?

atypical bilayer (phospholipids inside and phospholipid and liposaccharides outside)

19

What is the outer layer of the outer membrane called?

The LPS layer

20

Describe the LPS layer

lipid A linked to a polysaccharide by 2-ketodeoxyoctonate

21

What is lipid A?

lipid moiety, toxic to animals (causing inflammation and sepsis), and endotoxin that plays a major role in pathenogenesis of Gram negative bacteri, contains 6 lipid tails embedded in the membrane

22

What is O-specific polysaccharide?

aka O-antigen; consists of repeating sequence of 2-4 monosaccharides, its diversity is key in the diversity of bacterial strains

23

Cell walls of archaea contain no ___ and usually have no ___. They may consist of ___, ___, or ___

peptidoglycan/outer membrane/PRO/polysaccharides/glycoproteins

24

What is pseudomeurin?

similar in structure to peptidoglycan/meurin but with N-acetyltalosamine-uronic acid instead of NAM and lacking D amino acids

25

Is the linkage between sugars in archaea susceptible to lysozyme?

No

26

some species of archaea have cell walls composed of repeating units of two or more sugars (___) but most consist of ___ and/or ___

heteropolysaccharides/PRO/glycoPRO

27

What is an S-layer?

aka the paracrystalline layer, in archaea it is a cell wall with a crystalline appearance, can also be in bacteria on top of the peptidoglycan or outer membrane

28

what is the capsule/slime layer?

synthesized by some bacteria/archaea as extra protection, doesn't add significant strength to the wall, sometimes covalently bonded to the outer membrane or peptidoglycan layer, important in determining virulence (protects against host defences)

29

What makes up the capsule/slime layer?

polysaccharides or PRO, either heteropolysaccharides (most bacteria) or homopolysaccharides (some Gram negative)

30

What are flagella or fimbriae used for?

motility

31

one flagella=___, many flagella spread across the surface=___, many flagella on one end=___

monotrichous/peritrichous/lophotrichous

32

What are the rings of a Gram positive flagella?
What are the rings of a Gram negative flagella?
(order the from bottom to top)

- C-ring, MS-ring, P-ring
- C-ring, MS-ring, P-ring, L-ring

33

What powers the flagella movement?

proton motive force in the motor PRO and fil PRO

34

What are the steps of biosynthesis of a flagella?

1. C and MS-ring form
2. Motor PRO form
3. P-ring forms
4. L-ring forms
5. Early hook forms
6. Late hook and cap form
7. filament synthesizes between hook and cap

35

What are the types of movement of bacteria?

1. peritrichous: bundled flagella spin CCW, tumble CW, the spin CCW again
2. polar:
a. reversible flagella: CW to CCW
b. unidirectional flagella: CW, reorient, CW

36

Describe gliding motility

movement along a surface, either music secretion, lateral movement of surface adhesions, or type IV plus-dependant

37

Describe taxis

directed movement toward or away from a gradient of chemical or physical agents

38

What are the types of taxis?

chemotaxis (chemicals/nutrients/antibiotics), phototaxis (light), aerotaxis (oxygen), osmotaxis (ionic strength)

39

If theres no attractant present there is ___ movement, if there is an attractant present there is ___ movement

directed/random

40

What are fimbriae?

primarily involved in attaching microbe to surface, they form rigid, rod-like structures primarily in G negative

41

Describe fimbriae in G negative

- grow from the base
- anchored in outer membrane
- composed of piling
- not covalent, strand exchange
- needs accessory PRO coded with piling gene)

42

Describe fimbriae in G positive

- anchored in peptidoglycan
- composed of piling PRO
- covalently linked together
- assembled enzymatically (sortase)

43

What is an endospore?

highly differentiated ells that are extremely resistant to harsh environments, in dormant stage, easily dispersed

44

What are the parts of the endospore?

exosporium (PRO), spore coat (layers of spore-specific PRO), cortex (peptidoglycan), core/cytoplasm (Ca2+, DPA, SASPS), DNA, core wall

45

What is SASPS?

small acid-soluble spore PRO; bind ton DNA and protect it from damage (UV)

46

What id the purpose of DPA and Ca2+ in the endospore?

bind to water to dehydrate the core

47

Core of the endospore contains PRO needed for ___

germination

48

What are the steps of the sporulation cycle?

stage I: asymmetric division, commitment to sporulation
stage 2: septum divides perspire and mother cell
stage 3: engulfment
stage 4: cortex formation
stage 5: spore coat, Ca2+ uptake, SASPS, DPA
stage 6/7: maturation and cell lysis
germination follows

49

What are cell inclusions?

storage for energy reserves and building blocks, can be enclosed by single layer membrane (phospholipid, PRO, glycoPRO)

50

What are the storage nutrients form cell inclusions?

C, S, P

51

some cells use inclusions for ___

buoyancy

52

What is the name of the cell inclusions that contain magnetite and allow the bacteria to reposed to magnetic fields/

magnetosome