Flashcards in Bacteria and Archaea Deck (52)
What are the possible shapes of bacteria?
coccus, rod, spirillum, spirochete, budding/appendaged, filamentous
What is the purpose of cell walls?
allow bacteria to withstand intracellular osmotic pressure, responsible for shape and rigidity
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)
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
What is peptidoglycan?
polymer of peptidoglycan with many known variations
What is another name for peptidoglycan?
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)
What is the backbone of peptidoglycan made up of?
polymerized sugars (NAM and NAG)
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
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
Gram negative have ___ cross linking while Gram positive have ___ cross linking
what is another name for cross linking?
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
What is sortase?
the enzyme that covalently attaches wall associated PRO to the peptidoglycan
Describe the characteristics of the Gram negative cell wall
- 5-10% peptidoglycan
What is the periplasm?
space between cytoplasmic and outer membrane, contains peptidoglycan and a high quantity of PRO with specific functions
What is another name for the periplasm?
What is the outer membrane?
atypical bilayer (phospholipids inside and phospholipid and liposaccharides outside)
What is the outer layer of the outer membrane called?
The LPS layer
Describe the LPS layer
lipid A linked to a polysaccharide by 2-ketodeoxyoctonate
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
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
Cell walls of archaea contain no ___ and usually have no ___. They may consist of ___, ___, or ___
What is pseudomeurin?
similar in structure to peptidoglycan/meurin but with N-acetyltalosamine-uronic acid instead of NAM and lacking D amino acids
Is the linkage between sugars in archaea susceptible to lysozyme?
some species of archaea have cell walls composed of repeating units of two or more sugars (___) but most consist of ___ and/or ___
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
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)
What makes up the capsule/slime layer?
polysaccharides or PRO, either heteropolysaccharides (most bacteria) or homopolysaccharides (some Gram negative)
What are flagella or fimbriae used for?
one flagella=___, many flagella spread across the surface=___, many flagella on one end=___
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
What powers the flagella movement?
proton motive force in the motor PRO and fil PRO
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
What are the types of movement of bacteria?
1. peritrichous: bundled flagella spin CCW, tumble CW, the spin CCW again
a. reversible flagella: CW to CCW
b. unidirectional flagella: CW, reorient, CW
Describe gliding motility
movement along a surface, either music secretion, lateral movement of surface adhesions, or type IV plus-dependant
directed movement toward or away from a gradient of chemical or physical agents
What are the types of taxis?
chemotaxis (chemicals/nutrients/antibiotics), phototaxis (light), aerotaxis (oxygen), osmotaxis (ionic strength)
If theres no attractant present there is ___ movement, if there is an attractant present there is ___ movement
What are fimbriae?
primarily involved in attaching microbe to surface, they form rigid, rod-like structures primarily in G negative
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)
Describe fimbriae in G positive
- anchored in peptidoglycan
- composed of piling PRO
- covalently linked together
- assembled enzymatically (sortase)
What is an endospore?
highly differentiated ells that are extremely resistant to harsh environments, in dormant stage, easily dispersed
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
What is SASPS?
small acid-soluble spore PRO; bind ton DNA and protect it from damage (UV)
What id the purpose of DPA and Ca2+ in the endospore?
bind to water to dehydrate the core
Core of the endospore contains PRO needed for ___
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
What are cell inclusions?
storage for energy reserves and building blocks, can be enclosed by single layer membrane (phospholipid, PRO, glycoPRO)
What are the storage nutrients form cell inclusions?
C, S, P
some cells use inclusions for ___