Lab+4-+Selective+Media+and+Agar PDF

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microbiology foundation...

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“Lab 4 Selective Media & Agar”

“BIO250L”

Student Name: Click here to enter text. Access Code (located on the lid of your lab kit): Click here to enter text. “Experiment 1- Selection and Differentiation of Body Inhabiting, Gram-Positive Bacteria” “Table 4: Experiment 1 Growth Conditions” “Growth (Good or Poor)” “MSA Agar”

(Red or Yellow)”

“Other Observations”

Yes

Yes

Yellow

Fuzzy

“Nose”

Yes

Yes

Yellow

Clouded

“Countertop/Other”

Yes

Yes

Yellow

huge

“Control”

NO

No

Nothing

Nothing

“Surface Tested”

“Color “LB/Nutrient Agar”

“Skin”

“Post-Lab Questions” “1. What substance in MSA confers selectivity? Why?” MSA contains a high level of sodium chloride, which inhibits most bacteria from functioning, suggesting that this is selective. “2. What substance makes MSA differential? Why?” The MSA difference is enhanced by the use of mannitol in the fermentations. “3. What purpose does phenol red serve in MSA?” The phenol acts as a pH indicator. The bacterium is basic if the color is red. If the hue is yellow, fermentation has occurred and the solution is now acidic. “4. Why are the nutrient agar plates used in this experiment?” Nutrient agar was utilized in this study because it allows bacteria to grow and assess different forms of growth. “Insert photo of your cultures after incubation with your name clearly visible in the background:”

“Lab 4 Selective Media & Agar”

“BIO250L”

“Experiment 2- Selection and Differentiation of Gram-Negative Bacteria from Liquid Samples” “Table 5: MacConkey Agar Results” “Sample”

kombucha

water fountain (dispenser)

“Growth”

yes

.no

“Colony Color”

“Analysis”

colorless

Because of the colorless findings, lactose negative results were obtained..

n/a

There is no such thing as gramnegative. organisms

“Lab 4 Selective Media & Agar” faucet water

no

n/a

“BIO250L” There is no such thing as gramnegative. organisms

“Post-Lab Questions” “1. What ingredient(s) makes MacConkey agar selective for Gram-negative bacteria?” MacConkey's agar has two properties that make it gram-negative bacteria selective. It includes bile salts as well as crystal violet, which stops most gram-positive bacteria from growing. “2. What types of bacteria are inhibited on MacConkey agar?” Most gram positive bacteria are inhibited on MacConkey agar “3. What ingredient(s) makes MacConkey agar differential?” Lactose is the preferred sugar in MacConkey agar, and neutral red is used to measure acid formation. “4. Why is an indicator dye used in MacConkey agar?” MacConkey, like MSA, employs the dye as a pH indicator. When bacteria consume, they turn red, indicating that they are acidic producers. “5. What are some potentially pathogenic bacteria that are lactose fermenters that will grow on MacConkey agar?” Enterobacter, Escherichia coli, and Klebsiella “6. What are some potentially pathogenic bacteria that do not ferment lactose that will grow on MacConkey agar?” Salmonella, Shigella, and Pseudomonas “7. How would you verify that the colonies that grew on a MacConkey agar plate were Gram-negative?” Gram-positive organisms are prevented from growing because to the selective components. For lactose negative findings, the plate would display no color or be colorless. Lactose-positive foods are those that are colored. “8. Look up the formulation for MacConkey agar. Is this a chemically defined or complex media? Why is that important?” MacConkey is a multifaceted artist. This is due to the fact that the media is made up of lactose, a kind of sugar found in milk. However, we still don't know the full makeup of the microorganisms we're looking for, making it a difficult medium to work with. Because we don't know the makeup, it's critical to give a diverse diet. “Insert photo of your cultures after incubation with your name clearly visible in the background:”

“Lab 4 Selective Media & Agar”

“BIO250L”...