Module 2: Bacterial Anatomy Flashcards
What are the 3 shapes a bacteria might be?
Cocci, rod/bacilli, spirilla
What are the 5 characteristic arrangements of cocci?
Chains Clusters Pairs/diplococci Tetrads Sarcinae (cubes of 8)
What shape might the ends of a rod/bacilli be?
Rounded, square, pointed
What are coccobacili?
Short oval coccoid rods
Resemble rice grains
What are 3 characteristic arrangements of bacilli?
Palisades (sheets)
Acute angels
Chains
What is an involution form of bacteria?
Strangely shaped bacteria, dead/dying
What might cause involution form bacteria?
Poor growth conditions, lack of nutrients, antibiotic treatment
What is a bacterial colony?
Macroscopic group of bacteria
Divide and grow to visible entity on agar plate
What is cellular morphology?
Microscopic appearance of the bacteria on a gram stain
What is colonial morphology?
Macroscopic appearance of bacterial colonies on plate
Color, consistency, hemolysis, size, edge appearance, etc
What are flagella?
Bacterial appendage that allow movement
What are flagella made of?
Hollow core surrounded by flagellin protein
Attached to bacteria by basal body
What is a bacteria with no flagella called?
Atrichous
What does atrichous mean?
No flagella
What is a bacteria with 1 flagellum called?
Monotrichous
What does monotrichous mean?
1 flagellum
What kind of movement does a monotrichous bacteria have?
Directional
What kind of flagella would a bacteria with directional movement have?
1 flagellum, monotrichous
or
Up to 6 flagella, “tuft”, lophotrichous
What does lophotricous mean?
Lopho = tuft
Up to 6 flagella on one end
What is a bacteria with up to 6 flagella on one end called?
Lophotrichous
What kind of movement would a lophotrichous bacteria have?
Directional
What does amphitrichous mean?
Amphi = both
Flagella on both ends
What is a bacteria with flagella on both ends called?
Amphitrichous
What kind of movement would an aphitrichous bacteria have?
Tumbling, spilling
What kind of flagella would a bacteria with a tumbling and spinning movement have?
Amphitrichous = both ends
or
peritrichous = all around
What does peritrichous mean?
Peri = around
Flagella all around the bacteria
What is a bacteria with flagella all around it called?
Peritrichous
What kind of movement would a peritrichous bacteria have?
Tumbling, spinning
What bacteria have flagella? What bacteria do not?
Rods and some spirillum
Cocci do not
What do some spirillum use to move?
Axial filaments wrapped around the cells
Why do moving bacteria often stop?
They must “rest” and generate more energy to move
How are flagella detected?
A flagella stain must be done in order to see them on light microscope
or
Electron microscopy
What is the technique used to stain flagella?
“Tar and feather”
Stained with tannic acid to make flagella sticky
Stained with carbol fuchsin or crystal violet
How is bacterial motility detected?
Slide motility - viewing liquid culture under microscope
Motility media - soft medium inoculated straight down, color spreading indicates movement
How is a slide motility test done?
From broth culture using hanging drop or flat slide
Hanging drop suspended over well
What type of sample must be used for a slide motility test?
Pure culture in log growth phase
In nutrient media with phosphate buffer, pH 6.8-7.0
Incubated overnight at room temperature
How are slide motility tests examined?
Microscopically at 40x on a light microscope
*Phase contrast may make it easier to see
What types of movement may be seen in a slide motility test?
Brownian movement - saline bombarding with bacteria, vibrating/jiggling
Drifting/streaming - flowing of liquid towards the edges in a fresh prep
Bacterial movement - moving across the field or upstream
What are the advantages of a slide motility test?
Rapid results after culture is grown
Possibly able to tell flagellar arrangement
What are the disadvantages of a slide motility test?
Tedious and slow for large volume
Bacteria may not show motility if culture is past the log phase
What is the medium used for a media motility test?
Semi-solid nutrient medium clear enough to see spread
0.2 or 0.5% agar makes it semi-solid
What are the 2 types of media motility tests?
Plate and tube
What is a plate motility test? How is it done?
Plate of medium is inoculated with one drop/spot of inoculum and incubated for 1-2 days then read for growth
What is a tube motility test? How is it done?
Motility medium is in a tube and inoculated with a straight wire by stabbing it down half way
Tubes are incubated for 1-2 days then read for growth
What can be added to motility medium to produce color to show motility? How does it work?
Triphenyltetrazolium chloride (TTC) Colorless to red when reduced by bacterial growth
What are the advantages of using a media motility method?
Fast and easy to set up
Time and temperature can be manipulated for optimum conditions
What are the disadvantages of using a media motility method?
Obligate aerobes require oxygen and will not grow well below the surface of the medium
Must incubate for many hours to get a result
What is a capsule?
Made of glycocalyx (polysaccharide, polypeptide, or both)
Organized and firmly attached to bacteria cell wall
What is a slime layer?
Glycocalyx that is not firmly attached bacteria cell walls
What do capsules do?
Virulence factor
Interfere with phagocytosis
Sticky and allow the bacteria to attach to surfaces
How does bacteria that is capsulated appear as a colony?
Slimy, wet, mucoid, glistening appearance
How can capsules be demonstrated?
On gram stain
Negative staining (India ink)
Capsular swelling/Quelling reaction (antibodies)
What are the problems associated with trying to demonstrate capsules in a gram stain?
Shrinkage!
Capsules contain mostly water, dying and fixing causes shrinking
What is negative staining for capsules?
The cell is unstained but the capsule will stain
Most bacterial stains, India ink
What do capsules look like in a gram stain?
With sufficient background staining capsules appear as clear halos
What is capsular swelling/quelling? How does it work?
Anticapsular antibodies attach to the capsule and make it appear larger, and able to visualize
What is capsule development link? What happens when the capsule disappears?
Present in vivo and on intial culture medium but may be lost on other media
Require good carbon and energy sources for production
Sucrose added to media can promote production