Lab One Flashcards
How is tryptic soy broth prepared?
70ml of distilled water is added to 4.2ml of TSB powder and mixed to dissolve and then another 70ml of distilled water is added
What colour is tryptic soy broth?
light brown
what is the feature of a none sterile liquid?
it is turbid (cloudy)
what is a feature of a sterile liquid?
it is not turbid (clear)
what was the only sterile broth in the sterillity lab experiment?
The bottle with the lid that was autoclaved
what can cause a culture to be non sterile?
contamination from air, non-sterile container, non-sterile broth
how is Tryptic Soy Agar prepared?
Agar is added to Tryptic Soy Broth, and then autoclaved to dissolve the agar and sterilize it. This is done under aseptic technique.
what is the pH of tryptic soy agar?
7.3 +/- 0.2
what is the formula of tryptic soy agar?
Tryptone (panreatic digest of casein) 17.0g
Enzytmatic digest of soybean meal 3.0g
Sodium chloride 5.0g
Di-potassium hydrogen phosphate 2.5g
Glucose (dextrose) 2.5g
Distilled water 1000ml
what percentage of agar is added to the tryptic soy broth?
1.5%
why is aseptic technique used?
to prevent the microbial contamination of laboratory workers, contamination from the environment they are working in and contamination of the species they are working on
when is aseptic technique used?
whenever specimens are to be transferred between media
what is subculturing?
use of aseptic technique procedures to maintain a pure culture when transferring microorganisms from media containing culture to fresh media not containing culture
what is the first step in subculturing?
plate streaking is the first step in subculturing to ensure that the bacteria is pure, followed by microscopic examination
what are the four subculturing procedures?
solid to solid- plate culture to plate
Solid to liquid- plate cultre to broth
Liquid to solid- broth culture to plate
Liquid to liquid- broth culture to broth
what is the procedure of subculturing into a liquid media?
- agar plate, agar side up
- lid lightly loosened on the culture
- flame the loop tp sterilize and allow to cool
- remove the lid from the culture and flame the opening, do not put the lid down on the bench
- move the loop up and down on the side of the broth container
- flame the top of the bottle and replace the lid
- flame the loop
(loosen the lid slightly before incubation)
what do you do to the lid of a bottle before incubation?
loosen it slightly to account for the build-up in pressure when inside the autoclave
what is the procedure for subculturing onto a solid culture medium?
- place both plates agar side up
- flame the loop and allow to cool
- touch the loop to an isolated colony on the agar surface
- use the streak plate method
what is the streak plate method?
- streaking a portion of the agar plate with an inoculum
- further portions of the plate are streaked to dilute the inoculum to form single colony-forming units (CFUs), which give rise to isolated colonies
what are CFUs?
colony-forming units.
each colony-forming unit gives rise to an isolated colony
when are the times to flame the loop in the streak plate method?
before picking up the inoculum
after streak 1
after streak 3
what are proteus?
bacteria that are classified by being rapidly motile
what is the structure of a proteus?
has a flagella that is visible when starined with a flagella stain
how do protues move look on an agar plate?
when inoculated at the centre or agar, they swarm and form concentric rings
why do proteus form the concentric ring pattern?
the concentric ring pattern occurs due to the cyclic repetition of alternating phases, swarming, active migration and consolidation
what are the two cell types that a proteus can be in?
Swimming or swarmer cells
what are the freatures of a swimmer proteus cell?
swimmer cells are shorter and oligoflagellated
what are the features of swarmer proteus cells?
swarmer cells are elongated and hyperflagellated
what effects the formation of the concentric ring pattern?
concnetric ring formation is sensitive to temperature, agar concentration, medium enruchment and bacterial density
what does not effect the formation of concentric rings?
nutrient glucose depletion does not alter the formation of concentric rings
what is the ideal temperature for commensal species isolated from the human body?
35 +/- 2 degrees
what is the ideal temperature for many bacteria that are isolated form the environment?
usually 20 or 25+/- 2 degrees
what effect does temperature have on the bacteria Serratia?
Higher temperature means that pigment formation is reduced
how does a change in nutrient availability affect the bacteria Serratia?
if sucrose is available, extracellular polymeric substances are overproduced and the colonies are domed
how can available nutrients affect bacteria?
it can alter the cell morphology
what should be on the x axis of a graph?
The horizontal (x) axis should be a linear scale and contain the independent variable
what should be on the y axis of a graph?
the vertical (y) axis is a logarithmic scale and contains the dependent variable
what should a graph always have?
always have a title and all species names should be underlined
the units must also be specified
can you tell if a broth culture is pure by looking at it?
No, you can’t tell if there is only one type of bacteria or if many present
what are the reasons that single colonies may not be present on a streak plate?
the loop what too hot and killed the bacteria
there were too much bacteria on the plate (the loop wasn’t flamed between streaks)
