Bacteria studies Flashcards
(46 cards)
1
Q
eukaryotes
A
- mostly linear chromosomes, in nuclear memebrane
- organelles
- polysaccharide cell walls (id present) chitin - animals cellulose plants
- mitosis
2
Q
prokaryotes
A
- mostly circular chromosomes, no nucleus
- no organelles
- peptidoglycan cell walls
binary fission
3
Q
gram negative
A
pink
4
Q
gram positive
A
purple
5
Q
cell wall structure
A
- threads of repeating carbohydrate (NAG-NAM)
- glued together with proteins
- these sugars and proteins form a compound called peptidoglycan
6
Q
gram-positive cells
A
- multiple layers of peptidoglycan (up to 80 nm thick)
- teichoic acids aid in keeping the layers together
- also increase the - charge of the cell wall
- allow for repulsion or binding on the cell wall
7
Q
gram-negative cells
A
- single layer of peptidoglycan (about 8nm thick)
- a second phospholipid membrane outside the peptidogllycan
- this membrane helps to repel some immune system factors, block entry of antibiotics and can contain toxic compounds
8
Q
bacterial staining
A
- gram stain
- acid fast stain
- negative stain
- flagella stain
- endospore stain
9
Q
bacterial smears
A
- usually the first step in staining
- mix a colony of bacteria with a drop of water or place a drop of liquid culture on the slide
- allow to air dry
- quickly heat fix by passing over a flame for a 1-2 seconds (the heat will adhere the cell surface to the glass while keeping most of the structures intact
10
Q
steps 1-4
A
- crystal violet (primary stain added to specimen smear)
- iodine (mordant makes dye less soluable so it adheres to cell walls)
- alcohol (decolorizer washes away strain from gram - cell walls)
- safranin (counterstain allows dye to adhere to gram - cell walls
11
Q
gram staining difficulties
A
- older cultures have weak cell walls
- older solutions may not work properly(iodide and light sensitivity)
- decolorization timing
- excessive counterstain can displace CV
- some bacteria are gram variable
12
Q
aseptic technique
A
- prevention of contamination when cultivating microorganisms (and also containment of organims you are working with
- requires diligence as bacteria, yeast, molds and other organisms are virtually everywhere
13
Q
wire loop and sunsen burner
A
- loop is the most common way to transfer bacteria
- straight wire and sterile toothpick is also used
- flame is the most common way to keep things sterile
14
Q
fire rules
A
- always flame your loop before and after use
- retained heat can still kill cells
- do not wave loop to cool it down
- air currents next to the flame keep the air less contaminated - prone
- pilates should be kept inverted and opened only when ebing actively used
- tubes should be flamed before and after use
- tube caps shouldnt be set down
15
Q
acid fast stains
A
- waxy cell walls repel gram stains (and many antibiotics)
- primary dye is carbol-fushin (which has a high affinity from waxy mycolic acids)
- decolorization with an acid alcohol removes dye from most cells
- counter stain with methylene blue
16
Q
external structure: glycocalyx
A
- outside the cell wall
- increase pathogenicity
- composed of sugar and proteins
- a capsule is neatly organized
- a slime layer is unorganized and loose/diffuse
- can allow attach,emt to a surface by production of a biofilm
17
Q
negative stain
A
- allows visualization of glycocaryx
- nigrosin or congo red acidic dyes
- size and charge prevent binding to or penetrating bacteria
- thin film preparation
- cells are not fixed
- proper lighting and contrast can show cells, but stain variations that also stain cells can be used
18
Q
flagella stain
A
- used for motility
- 10-20 nm in width
- maximum resolution for a light microscope is 200 nm
- visualization with a light microscope requires thickening of the flagella
- leifson stain - crystal violet dye + a mordant [ phenol, tannic, KAI (SO4)2]
19
Q
atrichous
A
none
20
Q
mono
A
one
21
Q
amphi
A
both ends
22
Q
lopho
A
tufts
23
Q
peri
A
surrounding
24
Q
endospores
A
- a dormant daughter cell which is formed inside the main cell (doesnt make multiple, get 1 from 1 bacteria)
- resists drying out, heat, chemicals and radiation
- is not alive, all cellular processes are halted
- two most known groups are bacillus and clostridium
25
endospore stain
- use moist heat to stain the endospore wall
- primary stain is malachite green flooded onto a slide over a steaming water bath for 5 minutes
- rinse with cool water
- counterstain with safranin
- they hatch and push cell out of spore coat
- they all germenate at the same time
26
what is important when growing bacteria
- number, not size
- physical factor affect growth = temperature, salinity(most bacteria need salt below 2%), pH and nutrients
- each species has a range of conditions where growth is possible and more specific conditions where growth is optimal - reflecting the nature of their biome
27
culturing bacteria
- growing bacteria in the lab we need to be aware of the growth requirements of the species of interest
- nutrients, temperature, gasses (O2 and CO2) and illumination might be things which need tight regulation for optimal growth
28
complex media
- we are not aware of every chemical in the media
- partially digested beef
- ground up dry yeast
- less regulated
29
defined media
- every chemical in the media is known and quantified (knows exactly what was in there)
- can be tailored to requirements of one species
- can even add or control presence of trace elements
30
broth
- grow large quantities
- difficult to check for purity
31
plate
- readily score and separate colonies
- does not store well
32
slants
- mini plates - for storage with smaller volume
- difficult to check for purity
33
semi solid deeps
- can score motility and oxygen requirements
- difficult to check for purity
34
agar for plates
- historically, gelatin plates were used, but they melted at too low temperatures and some bacteria could digest the gelatin
- agar is a carbohydrate isolated from the cells walls of red algae
- thermal hysteresis - melts at 85C and solitifies at 40C
- few organisms make agarose (marine)
- also used vegan gelatin
35
selective media
- will encourage the growth of some bacteria while preventing the growth of others
36
differential media
- will produce different visual cues as to the type of organisms growing
37
enrichment media
- is a type of selective media used to allow proliferation of rare bacteria in a mixed population (soil, feces)
38
common plates: MacConkey
- selective and differential
- selects against non enteric gram positives using bile salts and crystal violet
- contains lactose and pH indicators
- fermentors turn purple
- non fermenters stay creamy
- acid diffusion may spread into plate
39
common plates : MSA
- mannitol salt agar
- selective and differential
- high salts (10% halophiles)
- contained mannitol (a sugar alcohol)
- fermenters turn yellow, non fermenters stay red
- useful for detecting staphylococcus aureus
40
common plates : blood agar
- typically sheep
- enrichment and differential
- 5-10%
- TEST FOR HEMOLYTIC ACTIVITY
- cells which can burst red cells
- releases iron that tehe bacteria cells need
- hemolysis may be enhanced in low O2 environments
- alpha is discoloration in or under the colony by some bacteria which release H2O2 reducing Fe2 hemoglobin to Fe3 methemoglobin
- beta is clearing due to lysis of RBCs by bacterial enzymes halo around colony where the RBC are being digested
- gamma is no hemolysis
41
common plates: SDA
- saboraud dextrose agar
- similar to nutrient agar but with a high amount of glucose (4%)
- sugar and acidic pH (5.6) selects for yeasts and molds by inhibiting most bacteria
42
SIM deep
1. sulfure reduction - if H2S is producted it will react with ammonium iron (II) sulfate and turn back
2. indole production - if trytophan is metabolized it will produce indole
- indole can be detected by dripping kovaks reagent on top after incubation (red=positive)
3. motility - if cells grow away from the stab the cells are motile
43
not a media : oxidase test
- reagent tests for cytochrome 3 oxidase
- can the organism use oxygen to generate
- disks or strips are wetted, a colony is applied and color change is observed over a few minutes
- purple/blue = +
- no change = -
44
putting together dichotomous keys
- a series of yes/no observations to quickly narrow the field of bacterial species to identify an unknown
- starts with general observations and becomes more specific
priority is given to tests that are
- universal, quick and simple
45
biochemical identification systems: several tests at once
- used to easily identify medically important bacteria
- several metabolic tests done at one time
- + and - results are scored and the tally is looked up in a booklet for the species
- over 3000 codes
46
antibody testing
stripes and assaying if specific antibodies bind to unknown cells to determine identity
