Final Exam Lab Review Flashcards
what media is acidic and is great for the isolation of dermatophytes, fungi, and yeasts?
Sabouraud Dextrose Agar
what media is reliable for isolating Staph aureus from foods?
Baird-Park Agar
Who was Hans Christian Gram
inventor of the Gram stain, and the reason Gram is capitalized
what media is able to differentiate between homofermentative and heterofermentative LAB?
HHD
what is the OGYE agar used for?
selection and enumeration of yeasts and molds
when would you use PALCAM agar?
the isolation of L. monocytogenes from food items
which media supports good growth of lactobacilli in general?
MRS
What is the Muller Hinton Agar used for?
antibiotic susceptibility testing
what are some reasons that Muller Hinton Agar is great for antibiotic susceptibility testing?
- nonselective
- non-differential
- absorbs toxins released from bacteria
- loose so you get diffusion of antibiotic throughout the agar
what are the steps of the gram stain?
fixate. then:
1) flood slide with crystal violet for a minute then rinse
2) flood slide with iodine for a minute then rinse
3) flood the slide with decolorizer (ethanol) for a 30 seconds then rinse
4) flood with safranin for a minute then rinse
what species are involved with yogurt production?
Streptococcus thermophilus & Lactobacillus Bulgaricus
Which species has a bi-phasic growth curve in yogurt production?
S. thermophilus
which species has a longer initial lag time in yogurt production? why?
L. bulgaricus. it isn’t until it receives growth factors (formic acid & CO2) from S. thermophilus that L. bulgaricus is stimulated to grow faster
what was the idea of the maple syrup lab?
the syrups contained different amounts of water content, and the lab’s purpose was to observe the difference in their spoilage.
if maple syrup 1 had more water content than 2, what does that mean about their sugar contents?
1 has less sugar, 2 has more
which type of organism will be responsible for the spoilage of syrup 1 and 2?
syrup 1 (more water): bacteria syrup 2 (less water): mold
which syrup will have a rapid drop in pH?
the syrup spoiled by bacteria
what was the idea of the antibiotic resistance lab?
- samples taken from meat are plated on TSA agar supplemented with the antimicrobials, tetracycline and ceftiofur. any surviving colonies show a degree of resistance to these antimicrobials
- the isolated colonies are further tested for resistance on MHA plates with 4 different antimicrobial disks on them (tetracycline, ampicillin, erythromycin, streptomycin)
what is the usual CFU of microbes on raw meat products?
10^2 to 10^5 CFU/cm^2 of aerobic mesophiles
if you plate the homogenized meat samples onto plates containing tetracycline and ceftiofure, why are you only plating 10^-1 and 10^-3
the actual amount of bacteria that can grow in these conditions would be very small so we need these higher concentrations
why do we include ceftiofur on this plate?
it has veterinary applications in commercial agriculture, which is applicable to the purchased meats in the lab.
are all isolates resistant to tetracycline?
If you isolate something on a plate containing tetracycline and then test using a tetracycline disc, you might not always see resistance. They are all resistant to tetracycline at some degree if you isolated them on a plate containing it, but there’s a higher concentration used on the disc
what is the purpose of the easy fermenting lid in sauerkraut production?
- prevent entrance of O2 to maintain anaerobic conditions
- enable exit of CO2 so the container doesn’t explode
what’s the purpose of adding salt in the initial sauerkraut culture
1) Selects for growth of LAB which are more resistant to more saline conditions
2) draw out juice from leaves to make sugars and nutrients readily available to LAB
how many campden crush tablets do you add to your apple/water mix? why?
ONE
- kill wild yeast
- dechlorinate
- act as antioxidant
what should your airlock look like about 24 hours after adding yeast?
some bubbles, popped off top
if you are not seeing CO2 discharge during your wine ferment, what could be the problem? what may be the result?
you likely have a stuck ferment. the result can smell like sulfur and you won’t get an ideal alcohol content
