Module 2 Flashcards
Cellular Morphology
size, shape, arrangement
um (micrometer)
1/1 000 000 meter
Average Cell Sizes
Average Cocci 1um X 1um
Average Rod 0.5umX3um
Cocci
Mostly round (some oval) Can be seen in Chains, "grape like" clusters, pairs/diplococci, Tetrads (4), Sarcinae (8)
Rod
Can be seen as palisades (bacterial lay in sheets), acute angles, chaining
Coccobacilli
Short, oval coccoid rods
If bacterium is longer than it is wide, call it a rod!
Spirilla
slightly curved to a tight corkscrew
*don’t chain
Involution Forms
Dead, degenerating or dying bacteria
Result of poor growth conditions, antibiotic treatment
Bacterial Colony
Group of bacteria that divide and grow together to form visible entity on agar plates.
Colonial Morphology
Macroscopic appearance of bacterial colonies on agar plates
Color, consistency, hemolysis, size, colony edge appearance
Beta Hemolysis
Toxin in bacteria causes a clearing of RBC in agar plate surrounding the colonies on a plate
Flagella
Long appendages that enable the cell to move
*No flagella on cocci, rods only
Cannot be seen under light microscope unless stained
Can be seen with electron microscope
Atrichous
No flagella (trichous=hair)
Monotrichous
one flagella
Directional, rapid darting
Lophotrichous
tuft (up to 6 flagella)
Directional, rapid darting
Amphitrichous
Flagella on both ends
Peritrichous
Flagella around the cell
Cell is pushed in all directions, giving slow, non-directional movement, spinning, tumbling motion
Slide Motility
look at a liquid culture microscopically and see if bacteria move
nutrient broth, phosphate buffer
pH6.8 to 7.0
Incubated at RT overnight
Brownian Movement
Caused by molecular bombardment by saline molecules against the bacteria
Bacteria appear to vibrate/jiggle
Drifting or Streaming Movement
Everything moves in direction with the flow of the liquid
Advantages to Slide Motility
rapid results once the bacterial have grown in broth
may be able to tell flagella arrangement based on type of movement
Disadvantages to Slide Motility
Tedious and slow for large amounts of tests
Bacteria may not show motility if culture has gone past log phase
Motility Media - Plate Method
Outdated, spot of inoculum placed at edge of plate. Incubated and read for spreading growth across plate
Motility Media - Tube Method
Most common method, inoculated with straight wire halfway down tube. Incubated and read for growth.
Triphenyltetrazolium Chloride (TTC)
May be added to motility medium. TTC changes colour from colourless to red when reduced by bacteria
Advantages to Media Method
Fast and easy
Tubes may be incubated for several days and temperature may be varied
Disadvantages to Media Method
Obligate anaerobes that require oxygen for growth do no grow very well below the surface of the medium
Capsules
Glycocalyx - a polymer composed of polysaccharide (or polypeptide or combo of both)
organized and firmly attached to the cell wall
Appear mucoid and slimy in colonies
Initial culture will have more capsules than subsequent in vitro cultures
Capsule does not pick up stain (remains a colourless “halo” around cell)
Slime Layer
Unorganized “capsule”
Function of Capsules
Interfere with phagocytosis
More virulent than non-capsulated bacteria
Provide protective layer for bacteria
Allows bacteria to attach to surfaces
Capsular Swelling/ Quellung Reaction
When capsules are too small to be seen with light microscope, anti capsular antibody attaches to surface, making the capsule seem larger.