Lecture 2 Flashcards
coccus (pl. cocci)
- spherical/ovoid
“strepto/staphylo”
rod
- cylindrical shape
“bacillus”
spirilla
spiral shape
pleomorphic
bacteria that can assume several shapes
(insert image - slide 6)
- hypha and stalk
- budding and appendaged bacteria
(insert image)
filamentous bacteria
“diplo-“
ex. diplococci
2
“strepto-“
ex. streptococci
2+
“staphyl-“
ex. staphylococcus aureus
grape clusters
“dipto”’
ex. diptobacilli
“strepto”
ex. streptobacilli
attached end to end
palisade
fence
(insert image)
v-shape
petidoglycan
- polysaccharide composed of N-acetylglusoamine (NAG) and N-acetylmuramic acid (NAM) linked by peptide bridges
- sugars + AA
- rigid layer makes up cell wall
lysozyme
- breaks down glycosidic bonds
- to control growth of bacteria
compare gram-positive vs. gram-negative cell walls
- peptidoglycan (PG)
- teichoic acid (TA) and lipoteichoic acid (LTA)
- membrane
- periplasmic space
- others (ie. LPS)
gram-positive - thick PG (10-100 nm) - TA linked to PG; LTA anchored to membrane - single membrane very thin (<15 nm) periplasmic space
gram-negative
- thin PG (2 nm)
- no TA or LTA
- inner and outer membrane
- periplasmic space
- LPS on surface
capsules and slime layers
polysaccharide layers that assist in attachment to surfaces, evasion of the immune system, and resistance to dessication
teichoic acids (anchors)
- acidic substances
- negatively charged attracts Na+, Ca++, Mg++
- provide rigidity by attracting cations
- role biofilm formation
lipoteichoic acids
techoic acids covalently bound to membrane lipids
lipopolysaccharide (LPS) layer
lipid A + core polysaccharide + O-polysaccharide
endotoxin
toxic component of LPS (lipid A)
porins
channels for movement of hyrophilic low molecular-weight substances
periplasm
space between cytoplasmic and outer membranes
capsule and slime layers
polysaccharide layers that assist in attachment to surfaces, evasion of the immune system, and resistance to dessication
fimbriae
finger-like projections; filamentous protein structures that enable organisms to stick to surfaces/ form pellicles
pili (and Type IV pili)
[insert image]
- straw/tube-like, longer than fimbriae
- filamentous protein structures that assist in surface attachment and facilitate conjugation (genetic exchange)
- Type IV: twitching motility
flagella
locomotion
Gram Stain
- developed by Hans Christian Gram in 1844
- to differentiate between Gram-positive and gram-negative bacteria
- bacterial suspension dried on glass slide
- crystal violet (1 min). wash off.
- iodine (1 min). wash off.
- 95% alcohol (10 s). wash off.
- safranin (30 s)
gram-positive = violet (retains stain) gram-negative = red (loses stain)
mordant
iodine
stain
- crystal violet
- safranin/fuschin
de-colourizer
- dissolve outer membrane to allow crystal violet to leach out
- acetone-alcohol
