Lab Practical 1 Additional Review Flashcards
Culture
a medium that contains living microbes
What are some general practices you should adhere to when performing an aseptic transfer? (7)
- Minimize potential contamination (do not do transfers over your books or bags)
- Be organized (arrange all media in advance and clearly label with your name, date, the medium, and the inoculum)
- Place all media tubes in a test tube rack when not in use whether they are sterile or not.
- Take your time (work efficiently, but do not hurry)
- Never hold a tube culture by its cap.
- Hold the inoculating loop or needle like a pencil in your dominant hand and relax.
- Adjust your Bunsen burner so its flame has an inner and outer cone.
Sterilization of inoculating instruments is done in what part of the Bunsen burner flame?
The hottest part of the flame - the tip of the inner cone
Heat-fixing bacterial smears on slides and incinerating the mouths of open glassware items are done in what part of the Bunsen burner flame?
the outer cone of the flame
When are broths generally used?
to grow microbes when fresh cultures or large numbers of cells are required.
What are agar slants generally used for?
to grow stock cultures that can be refrigerated after incubation and maintained for several weeks
What are plated media typically used for?
obtaining isolation of species, differential testing, and quantifying bacterial densities
What are the steps to transfer a broth culture to a sterile broth?
- Label the sterile broth tube (name, date, medium, and organism)
- While holding the inoculation loop in your dominant hand, flame the loop and wire from base to tip until uniformly orange-hot
- With your free hand pick up the culture tube and suspend the organisms by gently mixing.
- Remove the tube’s cap with the little finger of your loop hand and, holding it at an angle, flame the tube’s lip by passing it quickly through the flame a few times.
- move the tube under the inoculating loop and place the cooled inoculating loop into the broth and remove it being careful not to catch it on the tube’s lip (there should be a film of broth in the loop)
- Again flame the tube’s lip, replace the cap, and return the tube to the test tube rack.
- With your free hand pick up the sterile broth tube and remove the cap with the little finger of your loop hand.
- Hold the sterile broth tube at an angle and flame the lip.
- Move the tube under the inoculating loop and place the inoculating loop with the film of broth on it into the sterile medium and mix.
- Withdraw the loop from the broth and while still in the tube tap the film out of the loop before removing it completely.
- Again flame the tube’s lip, replace the cap, and return the tube to the tube rack.
- Flame the wire and loop again as before
- Incubate the inoculated culture at the assigned temperature for the assigned time.
How is transferring from an agar slant different than from a broth?
- no need to suspend the organisms as they are in a more solid form
- when flaming the tube at a slant you need to make sure the agar surface is facing upwards
- instead of dipping the inoculating loop into a liquid broth you carefully place it in the tube over some growth and then touch it to the agar surface in order to pick up a very small amount of the growth.
4 when inoculating your sterile agar slant you move the tube up the inoculating loop wire until the loop is at the base of the agar and slowly remove the tube from over the wire making a zigzag pattern in the agar with your loop.
What are the steps when transferring from a plate culture to a sterile broth or agar slant?
- label the sterile tube with your name, date, medium, and organism
- While holding the inoculation loop in your dominant hand, flame the loop and wire from base to tip until uniformly orange-hot
- leave the plate on the table and lift the lid OR with the plate inverted on the table, remove the base and hold it at an angle with the agar up.
- Touch the loop to the growth and obtain a small amount.
- Keeping the loop still, replace the plate lid
- Continue on with the normal inoculation procedure for a broth or slant.
What is a semi solid deep agar used for?
Used to grow bacteria that need less oxygen than is present on the surface of a medium. Also determines motility.
Does growth occur at different levels in agar deep?
yes
Consider agar slant, deep and broth cultures. Which can you see if it’s pure by just visually inspecting it?
Only agar slant, because the bacteria grows on the top and is all visible
Describe the growth pattern of a motile organism in a semi-solid deep.
There will be lateral growth of a motile organism. Growth will move away from the point of inoculation and will look like an inverted pine tree.
How will the arrangement of the staphylococcis epi. in broth differ from the arrangement in the slant culture?
broth will show turbidity, pellide or nocculent (or sedirrent) when arrangement in slant culture will show colonies and shape/ arrangement/ individual colonies
Why do you flame a loop?
Aseptic technique is used to insure that only your “microorganism” of choice is propagated.
Pathogen
A microorganism that resides on or in another species and causes damage to their host (causes disease)
Nonpathogenic
“free-living” - a microorganism that does not reside on or in a specific plant or animal host and are not known to cause disease
Commensal
microbes benefit from but have no significant effect on their host
Mutualistic
microbes benefit their host rather than damage them
Opportunistic pathogens
microbes that are capable of producing a disease state if introduced into a suitable part of the body.
Colony morphology: shape
- round (circular)
- irregular
- punctiform (tiny pinpoint)
Colony morphology: margin
- entire (smooth with no irregularities)
- undulate (wavy)
- lobate (lobed)
- filamentous (unbranched strands)
- rhizoid (branched like roots)
Colony morphology: elevation
- flat
- raised
- convex
- pulvinate (very convex)
- umbonate (raised in the center)
Colony morphology: texture
- moist
- mucoid (sticky)
- butyrous (buttery)
- dry
Colony morphology: pigment production
- color
- optical properties (opaque, translucent)
Colony morphology: surface
- smooth
- rough
- wrinkled (rugose)
- shiny
- dull
What are the advantages and disadvantages of using a slant?
The advantages of agar slants include providing bacterial storage over extended periods with a minimal risk of contamination or desiccation while disadvantages involve the organisms being less observable and accessible than those in petri dishes. Agar slants also lend themselves to the identification of bacteria by characteristic patterns of movement.
What terms are used to describe colony morphology? (7)
- Size
- Shape
- Margin
- Surface
- Texture
- Elevations
- pigment production
What terms are used to describe growth patterns on slants?
- Filiform
- pigmented
- friable
- spreading edge
- translucent/transparent
Filiform
growth that is dense and opaque with a smooth edge
Pigmented
colored
Friable
growth that is dry and crusty
Spreading Edge
growth that spreads at the edge (spreading margin)
What terms are used in application to broths?
- pellicle
- sediment
- uniform fine turbidity
- flocculent
flocculent
big chunks of bacteria
pellicle
a surface membrane produced when organisms float on top of the medium.
sediment
organisms sink to the bottom
uniform fine turbidity
organism concentrates light and makes illumination of specimen more uniform
Autotrophs
organisms able to survive with carbon dioxide as the only carbon source
heterotrophs
organisms requiring organic carbon
defined media
one in which the amount and identity of every ingredient are known, which means it must be formulated from purified chemicals.
undefined media
composed of extracts from, or digests of, plant or animal matter and are usually quite rich in nutrients; exact composition of the medium and the amount of each ingredient are unknown.
What are the three elements of major importance in regards to microbial growth?
carbon, nitrogen, and oxygen
