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
What do colonies look like once capsules are no longer forming?
Become smaller and dryer
Less virulent
What is the purpose of a cell wall?
Gives shape and protects the plasma membrane
Nutrients move through by passive diffusion
What is the cell wall of bacteria made of?
Peptidoglycan is strengthening substance
N-acetylglucosamine and N-acetylmuramic acid alternate to form carbohydrate backbone
What is the difference in cell wall between gram positive and gram negative bacteria?
Gram positive have a thick peptidoglycan layer and teichoic acid
Gram negative have a thin peptidoglycan layer which is attaches to an outer phospholpid bilayer with lipopriten
What can damage the bacterial cell wall?
Some antibiotics like Penicillin
Bodily enzyme lysozyme
Which bacteria is more susceptible to cell wall damage?
Gram positive as the peptidogylcan layer is exposed
What are gram positive and gram negative bacteria called when they do not have a cell wall? What happens to them?
Gram positive - protoplast
Gram negative - spheroplast
Susceptible to osmotic lysis
What is a hypotonic solution? What happens to cells in a hypotonic solution?
More water (less salt) in the solution than in the cell Water rushes into the cell causing lysis
What is a hypertonic solution? What happens to cells in a hypertonic solution?
Less water (more salt) in the solution than in the cell Water rushes out of the cell causing shrinkage and collapse
What is an isotonic solution?
Solution with the same amount of water and salt as the cell
What gives the best typical cell arrangements for a gram stain?
A gram stain from a broth culture
What is a direct film/smear?
Gram stain prepared directly from the patients sample
ex: sputum, swab, etc
What is the purpose of a direct smear? What happens if it is too thick or too thin?
Used for preliminary diagnosis
Too thick will cause unclear cellular detail
Too thin will not represent the cells and some may be missed
What does fixation of the gram stain do? What types of fixation can be used?
Sticks the bacteria to the slide, kills bacteria, makes cells more permeable to stain, prevents autolysis
Alcohol (methanol) or heat fixation (hot plate, Bunsen burner)
What is the advantage of alcohol over heat fixation?
Bacteria are preserved closer to their true morphology
What happens if a gram stain is not fixed or under-fixed? Over-fixed?
Under-fixed - bacteria washed off or poorly stained
Over-fixed - Poor staining, usually pale, shapes altered/involution forms
What stains can be used for a gram stain?
Crystal violet, methyl violet, gentian violet
What type of dye is the purple dye used in the gram stain?
Basic pararosaniline dye
Dissolved in alcohol
What is the purpose of iodine in the gram stain?
Fixed crystal violet by forming a lake (is a mordant)
What may be seen on a gram stain other than bacteria?
PMN’s, epithelial cells, red blood cells, mucous
What chemical test can be used to determine a bacteria’s gram reaction? How does it work?
KOH test
1 drop of KOH, stir in colony
Gram negative form viscid thread when stick is pulled away because it has more lipid
How can susceptibility be used to determine a gram reaction?
If growth is inhibited by gram positive or gram negative spectrum antibiotics
What might cause disruption of the cell wall and cause poor gram staining?
Lysozyme
Rough handling when preparing the slide
Old cells
Antimicrobials that inhibit the cell wall
What is a plasmid? What does it do?
Extra chromosomal piece of genetic material, can be gained or lost
Carry genetic information not usually essential to survival
What genetic information might be on a bacterial plasmid?
Antibiotic resistance
Transferability of antibiotic resistance
Ability to decompose complex organic compounds
Production of harmful toxin
Allowing mating and genetic information exchange
What is fimbriae? What does it do?
Non-flagellar hair like projections on cells
Allows surface adhesion (virulance factor)
What is a pili? What does it do?
Forms conneection between bacteria cells to move DNA between them
Found only on gram negative bacteria
AKA sex pili
What is a bacteria’s plasma membrane made of?
Phospholipid bilayer with proteins
What is the function of the plasma membrane?
Selective barrier regulating what enters and exits the cell
Prevents large molecules but allows small ones, lipid soluble ones move easier
How do molecules move in and out of bacteria through the plasma membrane?
Diffusion, osmosis, facilitated diffusion, active transport
What is diffusion?
Passive movement from high to low conectration
What is osmosis?
Passive movement of water
What is facilitated diffusion?
Passive movement from high to low concentration by carrier enzymes called Permeases
What is active transport?
Movement from low to high concentration, requires energy
What is a spore?
Duplicated chromosome and small amount of cytoplasm surrounded by a spore coat
How are spores produced? What bacteria can produce them?
Produced when nutrients are depleted, starts in late log stage and during stationary and dying phases.
Only gram positive rods can produce spores
What is germination?
The spore turns into a cell, chemically triggered, begins with spore taking in water.
Eventually core splits and the vegetative cell emerges
How are spores seen in a gram stain?
Usually do not stain but can be steamed with certain stains
Appear as refractile unstained areas
How might a spores shape, location, and appearance be described?
Shape - spherical or oval
Location - central, subterminal, terminal, or free
Appearance - bluging or non-bulging
What is the function of spores?
Enables bacteria to resist adverse conditions
How do spores react to heat? Can they be destroyed?
Varying heat resistance, some require 121 degrees moist heat for 12-15 minutes
Autoclaving destroys spores
How do spores react to disinfection? Can they be destroyed?
Require better disinfectants and longer exposure times to destroy
How do spores react to lack of nutrients and drying?
Can survive for years without nutrients and moisture
What kind of particles might be present in a bacteria’s cytoplasm?
Ribosomes and inclusions (nutrient or energy reserves)
What are ribosomes? What is their function?
Free granules, 50S and 30S subunits join to form 70S ribosomes
Protein synthesis
What kinds of inclusions might a bacteria have?
Volutin/metachromatic granules - phosphate storage for ATP (mainly in Corynebacterium)
Polysaccharide granules - glycogen/starch, food storage
Lipid inclusion - few bacteria
Sulfur granules - energy reserve
One millimeter is equal to
a. 100 micrometers
b. 1,000 micrometers
c. 10,000 micrometers
d. 100,000 micrometers
b. 1,000 micrometers
Rod shaped bacteria that slip together and lie in sheets on top of each other after cell division are described as forming:
a. palisades
b. clusters
c. ivolution forms
d. tetrads
a. palisades
Bacteria that have a tuft of flagella at one end would be described as having the following flagellar arrangement
a. peritrichous
b. monotrichous
c. lophotrichous
d. amphitrichous
c. lophotrichous
Which of the following techniques would demonstrate the actual flagellar arrangement?
a. preparation examined with electron microscopy
b. gram stained preparation
c. slide motility test
d. medium motility test
a. preparation examined with electron microscopy
Which of the following would be an appropriate concentration of agar for motility medium?
a. 0.3 g/L
b. 3.0 g/L
c. 30 g/L
d. 300 g/L
b. 3.0 g/L
Bacteria in a wet preparation that vibrate in a limited area are showing
a. monotrichous motility
b. streaming
c. peritrichous motility
d. Brownian movement
d. Brownian movement
All of the following are true of the uses of triphenyltetrazolium chloride in motility medium except
a. in the colorless form when added to medium
b. turns the medium red where bacteria growth is present
c. reacts with glycocalyx of bacterial cells
d. may inhibit growth of some bacteria
c. reacts with glycocalyx of bacterial cells
An organism growing on blood agar as small colonies failed to grow in a motility tube with TTC after 24 hour incubation. What are 3 possible reasons for the “no growth” reaction
- Growth may have been inhibited by TTC
- May be obligate aerobe bacteria, cannot grow without air
- Inoculum bacteria may have been dead from old culture or missed the tube
In gram stained preparation, capsules appear as
a. clear refractile areas within the cell
b. clear halos around the cell
c. red areas around the cell
d. pink, refractile bodies within the cell
b. clear halos around the cell
The main components of most bacterial capsules are water and
a. polysaccharides
b. nucleic acid
c. polypeptides
d. phospholipids
a. polysaccharides
The following stain is used to demonstrate capsules in wet preparations
a. crystal violet
b. nigrosin/India ink
c. carbol fuchsin
d. safranin
b. nigrosin/India ink
The substance that gives bacterial cell walls rigidity is
a. teichoic acids
b. lipopolysaccharide
c. phospholipids
d. peptidoglycan
d. peptidoglycan
A protoplast differs from a typical bacterial cell in that it lacks a
a. cell wall
b. plasma membrane
c. capsule
d. nuclear membrane
a. cell wall
The reagents and stains used in the gram stain listed in order are
a. iodine, acetone, crystal violet, safranin
b. crystal violet, acetone, iodine, safranin
c. iodine, crystal violet, acetone, safranin
d. crystal violet, iodine, acetone, safranin
d. crystal violet, iodine, acetone, safranin
Which of the following would indicate a gram stain is over-decolorized?
a. debris is pink
b. cytoplasm of epithelial cells in pink
c. nuclei of white blood cells are red
d. none of the above
d. none of the above
The gram negative cell wall: (may have multiple answers)
a. is about 10 nanometers thick
b. contains peptidoglycan
c. has an outer phospholipid bilayer
d. contains teichoic acids
a. is about 10 nanometers thick
b. contains peptidoglycan
c. has an outer phospholipid bilayer
Fixation of slides before gram staining: (may have multiple answers)
a. makes cells permeable to stain
b. kills all endospores
c. sticks bacteria to slides
d. removes lipid from cell walls
a. makes cells permeable to stain
c. stick bacteria to slides
The following may cause gram positive bacteria to stain gram negative: (may have multiple answers)
a. preparing the slide from an old colony
b. leaving the decolorizer on too long
c. exposure of the bacteria to antibiotics
d. rupturing the cell walls when preparing the slide
all are correct
The following solutions may cause bacteria to swell and lyse
a. 0.50% sodium chloride
b. 0.85% sodium chloride
c. 0.25% sodium chloride
d. 5.0% sodium chloride
a. 0.50%
b. 0.25%
Decolorizers used for the gram stain include
a. alcohol
b. xylol
c. acetone
d. methyl etthyl ketone
a. alcohol
c. acetone
Pararosailine dyes used as the first solution in the gram stain include
a. safranin
b. methyl violet
c. lugol’s iodine
d. crystal violet
b. methyl violet
d. crystal violet
When examining gram stained slides of pure cultures of gram positive cocci there are usually a few cells staining gram negative. How could this be explained?
There are a few bacteria that are dead or have a weak cell wall causing decolorization
You are examining a gram stained slide of a single colony and note the bacteria are all gram positive and the background debris is a gram positive color. Can the bacteria be confidently reported as gram positive?
No the slide is under-decolorized
You have done a gram stain on a known gram negative organism. The bacteria are stained red and the background debris is pink. Can you tell if the slide has been over-decolorized?
No you could only tell if it was under-decolorized
You are examining a gram stained slide of Staphylococcus aureus and find the bacteria to be stained red and the background debris pink. Has the slide been properly stained?
No, it is over-decolorized
You are examining a gram stained slide prepared from sputum. The epithelial cells have dark purple nuclei and pink cytoplasm, white blood cells have blue-black nuclei and purple cytoplasm and both pink and purple bacteria are present. Has the slide been properly stained?
No, it is under-decolorized
When examining a gram stained slide under oil immersion the gram positive bacteria were stained pale and moving. What could be the reason?
The slide was not fixed
What would a gram stained slide loo like if you forgot the counterstain?
Gram positive bacteria will be stained but may be blue-black, gram negative bacteria and debris will be unstained
Which of the following structures enable some bacteria to attach to host cells?
a. capsules
b. fimbriae
c. pili
d. flagella
b. fimbriae
Which of the following is not a function of the bacterial plasma membrane?
a. osmosis
b. facilitated diffusion
c. active transport
d. protein synthesis
d. protein synthesis
The main component of the bacterial plasma membrane is
a. glycocalyx
b. phospholipid bilayer
c. polypeptide
d. lipoprotein bilayer
b. phospholipid bilayer
In gram stained films, fully developed spores appear as
a. refractile, unstained bodies within the cells
b. dark staining bodies within the cell
c. red structures within gram positive cells
d. unstained halos around the cell
a. refractile, unstained bodies within the cell
The only bacteria that form spores are
a. gram positive cocci
b. gram negative cocci
c. gram negative rods
d. gram positive rods
d. gram positive rods
Bacterial inclusions that are phosphate storage areas in side the cell are called
a. ribosomes
b. mitochondria
c. volutin
d. endospores
c. volutin
The bacterial chromosome
a. is double stranded DNA
b. in enclosed with a nuclear membrane
c. contains DNA and histones
c. is double stranded RNA
a. is double stranded DNA
A bacteria structure used extensively in DNA technology is
a. capsules
b. plasmids
c. endospores
d. pili
b. plasmids
Prokaryotic cells (may have multiple answers)
a. show streaming in the cytoplasm
b. may produce endospores
c. have endoplasmic reticulum with ribosomes
d. have peptidoglycan in the cell wall
b. may produce endospores
d. have peptidoglycan in the cell wall
The following are true of plasmids (may have multiple answers)
a. may carry genes for antibiotic resistance
b. single strand of RNA
c. replicate independent of the chromosome
d. part of the main chromosome of the bacterial cell
a. may carry genes for antibiotic resistance
c. replicate independent of the chromosome
Bacterial ribosomes (may have multiple answers)
a. are the sites of protein synthesis
b. consist of 2 subunits
c. are found in the cytoplasm
d. are found of the endoplasmic reticulum
a. are the sites of protein synthesis
b. consist of 2 subunits
c. are found in the cytoplasm
The following structures are common to both eukaryotic and prokaryotic cells
a. mitochondria
b. cytoskeleton
c. peptidoglycan
d. ribosomes
d. ribosomes
Some gram negative rods are seen to have refractile unstained bodies in the cells. Could these be spores?
Not if the gram stain is done properly, only gram positive rods can produce spores
Likely it has been over-decolorized
