Microbial Structure Flashcards
capsule
loose polysaccharide structure
protects cell from phagocytosis
protects cell from desiccation
pili/fimbriae
composed of oligomeric piling proteins
appendage used for bacterial conjugation forms tube/bridge to enable transfer of plasmids between bacteria
highly antigenic
plays role in attachment
Flagellae
organs of locomotion
composed of flagellin protein
20nm thick helical tube
driven by rotary engine at anchor point on inner cell membrane
spores
hard multilayered coats making spore difficult to kill
adapted for long term survival allowing regrowth under suitable conditions
triggered by adverse environmental conditions
slime
polysaccharide material
secreted by some bacteria growing I biofilms
protects against immune attack
protects against eradication by antibiotics
What is gram staining based off
chemical and physical properties of the cell walls
primary stain: crystal violet dye
stains all bacterial cells purple
trapping agent: grams iodine
forms CVI complexes in the cell wall
decolorisation: alcohol/acetone
interacts with lipids In cell wall
GRAM -VE = loses outer LPS layer; exposes thin inner PGN layer; coloured complexes mainly wash away
GRAM +VE = becomes dehydrated and traps the complexes in thicker PGN layer of cell wall
Counterstain: safranin
GRAM -VE = pink/reddish
GRAM +VE = Purple
Name me the cell wall components
Peptidoglycan PGN
Lipoteichoic Acid LTA
Lipopolysacchride LPS
Outer membrane proteins OMPS
Bacteria replication process
Reproduce by binary fission
Genetic information found in circular DNA
DNA is a self replicating molecule
Circular DNA - replication starts at ‘origin’
replicates in two directions
2 forks split off from origin and meet at bottom
4 phases of bacterial growth
Lag - small increase (active growth, reproduction)
Log - big increase (uniform replication)
Stationary - flat (exhaustion of nutrients)
Death - decrease
define transformation
some bacteria are capable of taking up DNA from their environment
define transduction
involves the exchanging of bacterial DNA through bacteriophages
conjugation
one bacterium connects itself to another through pilus
cocci
spherical
bacilli
rod shaped
spiral
helical rod
viral structure components
nucleic acid
capsid
envelope
spikes
capsid
protein coat/shell protein subunits capsomeres - aggregated protomeres shapes: - rod like - polyhedral -complex
envelope
amorphous structure lipid protein carb eg herpes
spikes
Glycoprotein projections arising from envelope
Glycoprotein projections arising from envelope
6 steps of viral replication
assembly - viral components and enzymes are produces and begin to assemble
maturation - virus fully develops
release
adsorption
virus binds to host/highly specific
penetration
virus injects into genome by:
- fission
- binding
- ingestion
replication
capsid digested by proteolytic enzymes, viral genome replicates using host cellular machinery
assembly
viral components and enzymes are produces and begin to assemble
release
occurs at site of nucleic acid replication
viral enzymes break down bacterial wall
from RNA as they are and DNA as cells autolyse and in inclusion bodies
• Viruses migrate to either plasma membrane or nuclear membrane
• Envelopes formed around nucleocapsids by “budding” of cell membrane
• Slow continuous release of mature viral particles • No inclusion bodies
3 main helminth groups important in humans
– Cestoda: tapeworms
– Trematoda: flukes
– Nematoda: roundworms
