Module 2: Bacterial Anatomy Flashcards
What is cellular morphology?
When bacteria is examined under the microscope for shape, size and arrangement.
What measurement is used to bacteria?
Micrometer. 1micrometer= 1000mm = 1x10-6 m
What are the three basic shapes of bacteria?
- Cocci (coccus) - ball shaped (size 1um X 1um)
- Bacilli (bacillus) - rods (size average 0.5um X 3um)
- Spirilla (spirillum or spirochetes). - spiral shaped rods.
What are cocci chains?
Bacteria cells divide in one plane only and adhere to each other after division. Eg. streptococci
What are cocci clusters?
When bacteria divide in several planes and adhere to each other to form grape like clusters. Eg. Staphylococci
What are diplococci?
Cocci that are arranged in pairs.
What are cocci tetrads and sarcinae?
Cocci that divide in two planes at right angles to each other to groups of four.
AND
Cocci that divide in three planes at right angles to each other to groups of eight - like grapes.
What are four different shapes that rods are?
- Rounded rods
- Square rods
- Pointed ends
- Short, oval coccoid rods are also called coccobacilli- look like rice grains.
Describe the rod-shaped bacteria arrangement palisades?
Bacteria that divide and sheet (on top of each other).
Describe the rod-shaped bacteria arrangement acute angles?
Bacteria snaps at point of division.
Define involution forms.
Dead, degenerating or dying bacteria. Happens from lack of nutrients or proper atmospheric conditions for growth or antibiotic treatment.
What is flagella?
Long filamentous appendages that allow movement 0.02 micrometers (not shown on gram stained slides). Gives bacteria moving patterns.
Flagella are found on some rods, but not on cocci.
What are the five flagellar arrangements?
Atrichous: No flagella
Monotrichous: Single flagellum on one end of bacteria (very directional movement)
Lophotrichous: Tuft of flagella on one end of bacteria (very directional movement)
Amphitrichous: Tufts of flagella on both ends of bacterial cell (spinning motion)
Peritrichous: Flagella all around bacterial cell (spinning motion)
What is slide motility of flagella?
When an organism is grown in pure culture in a liquid, once in log phase (actively motile) of growth a drop is looked at under 40X on microscope.
What is brownian movement of flagella?
molecules bombard bacterial cells and they appear to jiggle or vibrate.
What is drifting or streaming of flagella?
when everything flows in one direction.
What is real mobility of flagella?
when bacteria move against the flow of liquid.
Mobility media, what is plate media?
a semi solid media that is inoculated with bacteria, then incubated for 1-2day to allow growth. - more expensive method
Mobility media, what is tube media?
test tube of media is inoculated half way down with bacteria, then incubated for 1-2 days.
What is TTC (Triphenyltertrazolium chloride)?
may be added to aid in reading the test tube media test . If growth of bacteria occurs it will change to red color.
What are the components of bacterial capsules?
Viscous Layer or Glycocalyx: excreted from some bacteria
Chemical composition: Polysaccharide, polypeptide, or polysaccharide/polypeptide polymer
Capsule: when the glycocalyx is organized and firmly attached to the cell wall.
Slime Layer: when the glycocalyx is unorganized and loosely attached.
What are bacterial capsules 3 functions?
- Phagocytosis
- Increases bacterial virulence - better able to invade host
- Protective layer - allows adhering to host surfaces
When do you want to use negative stain with capsules?
when the part of the cell you wish to see is unstained.
What causes capsule shrinkage?
drying and fixing of slides, as well as heat fixation
What do capsules need for development?
Good carbon and energy sources
What is the function of a bacteria’s cell wall?
it is a rigid wall outside the plasma membrane that protects the plasma membrane and helps keep the shape.
What are the components of a bacteria’s cell wall?
Peptidoglycan- two alternating sugars joined together by amino acid chains.
NAG-NAM chain- sugars from the backbone
Tetra-peptide side chains- attach to NAM
Peptide cross bridges- 1-5 amino acids hat bond to tetra-peptideside chains.
Describe the gram positive cell wall.
- 30-60 (lots) peptidoglycan layer (thicker than gram negative)
- responsible for holding the crystal violet of gram stain.
- positive gram cells remain blue-black color after gram staining.
Describe the gram negative cell wall.
- outer phospholipid/liposaccaride layer
- lipoprotein links the outer layer with peptidoglycan (thin layer 7nm)
- Gram negative cell wall: Outer lipid layer prevents crystal violet from being retained or penetrating cell wall
- gram negative are red/pink because of the counterstain/`
What do antibiotics do to the bacterial cell wall?
The break down the peptidoglycan bonds. Eg. penicillin
-Gram positive are more susceptible to this because they have more peptidoglycan.
What is protoplast and spheroplast?
P- gram POSITIVE that has lost its cell wall.
S- gram NEGATIVE is lysed but there is still some of the outer membrane attached.
What is a hypotonic, hypersonic and isotonic solution?
Hypotonic solution: water moves into cell causing rupture or lysis, lower water concentration/higher salt concentration inside cell than outside
Hypertonic solution: water leaves cell causing shrinkage, higher water concentration in cell than outside
Isotonic solution: 0.85% saline (NaCl), same concentration as bacterial cells, no water movement
What are 4 things that fixation accomplishes?
- Fixes/sticks bacteria to slide
- Kills vegetative cells but not spores
- Makes cells more permeable to stain
- Prevents autolysis or changes in cells
What is the process of fixation?
- Air dry or warm slide completely after applying specimen
- Fix slide with bunsen burner(heat) or alcohol for one minute.
- Pour alcohol off and let slide air dry again before staining
Explain the gram staining procedure. (C.I.A.S.)
“C” Step 1: flood fixed slide with crystal violet for 1 minute, wash with water. All cells & bacteria are blue-purple.
“I” Step 2: flood slide with iodine for 1 min.– mordanting effect to fix dye into cells and bacteria. All cells & bacteria are purple-blue-black.
“A” Step 3: Decolorize with organic solvents such are ethanol, acetone-alcohol until no more blue comes off slide, wash slide immediately. Most important step
Result should be that gram POSITIVE cells are not decolorized and are still purple-blue & gram NEGATIVE cells are decolorized and are colourless.
“S” Step 4: Counterstain with safranin for 1 minute and wash off.
Result: negative = pink/red & positive = purple/blue black
What happens when over decolorization occurs?
Left on too long.
- Gram positives appear gram negative, too much crystal violet has been taken out of bacterial cells
- Gram negative bacteria, cells and debris will be still stain red
What happens when under decolorization occurs?
Not on long enough
- Gram negative bacteria and cells appear gram positive, not enough crystal violet has been removed from bacterial cells
- Gram positive bacteria are still stained blue
What are the function of plasmids?
- Resistance to antibiotics
- Transfer of resistance factors
- Decomposition of organics
- Production of toxins
- Mating and exchange of genetic info
Describe fimbriae and pili.
Fimbriae: Non-flagellar, hair-like projections on gram positive and negative cells. They adherence to surfaces and cells, important virulence factor.
Pili: Longer than fimbriae, “sex pili”, transfer of genetic material between bacterial cells
What are the components of the bacterial cytoplasm?
- 80% water
- Ribosomes: 50S and 30S subunits = 70S ribosomes for protein synthesis
- Volutin granules: phosphate for ATP
- Polysaccharide granules: glycogen, starch
- Lipids
- Sulfur granules: energy reserve
Which bacteria are the only ones that can produced spores?
Gram positive rods.
