Q: A triple scale hydrometer is used to estimate alcohol content in a fermentation. Which scale is typically used for this purpose, and how is the alcohol content calculated?

Specific gravity; $$\text{Alcohol} = (\text{Initial SG} - \text{Final SG}) \times 131$$

Question 1

Which microorganism is primarily responsible for the fermentation of wine and beer, and what is its main substrate?

Accepted Answer

Saccharomyces cerevisiae; glucose

Question 2

During yogurt production, which two bacterial species are commonly used as inoculum, and what is their primary metabolic by-product?

Accepted Answer

Streptococcus thermophilus and Lactobacillus bulgaricus; lactic acid

Question 3

Why is there little to no alcohol produced when making soda pop naturally?

Accepted Answer

Fermentation is stopped before significant alcohol accumulates

Question 4

What is the purpose of the trap in a fermentation setup for wine or beer?

Accepted Answer

To allow carbon dioxide to escape while preventing oxygen and contaminants from entering

Question 5

A triple scale hydrometer is used to estimate alcohol content in a fermentation. Which scale is typically used for this purpose, and how is the alcohol content calculated?

Accepted Answer

Specific gravity; $$	ext{Alcohol} = (	ext{Initial SG} - 	ext{Final SG}) 	imes 131$$

Question 6

Why are yogurt and cheese products acidic after fermentation, and what compound is responsible for this change?

Accepted Answer

Lactic acid is produced by bacteria fermenting lactose, lowering the pH

Question 7

What is homofermentation, and how does it apply to yogurt production?

Accepted Answer

It is fermentation that produces only lactic acid as the main by-product, as seen in yogurt

Question 8

Why do we use a Gram control on each slide during Gram staining, and which two organisms are typically used as controls?

Accepted Answer

To verify the staining procedure worked; Escherichia coli (Gram-negative rods) and Staphylococcus aureus (Gram-positive cocci)

Question 9

What is the main purpose of streaking a plate in microbiology?

Accepted Answer

To isolate individual colonies from a mixed culture

Question 10

Define a 'colony' in the context of microbiology.

Accepted Answer

A visible mass of cells derived from a single progenitor cell

Question 11

What is the primary goal of the Glyphosate 1 and 2 experiments in the lab?

Accepted Answer

To determine if environmental microbes can utilize glyphosate as a nutrient source

Question 12

If glyphosate affects the microbes in the rumen of cows, what could be a possible consequence for the cow?

Accepted Answer

Reduced ability to digest cellulose and obtain nutrients

Question 13

Based on the molecular structure of glyphosate, what essential element could it supply to microorganisms capable of utilizing it?

Accepted Answer

Phosphorus

Question 14

In the glyphosate enrichment media, how could you confirm that microbes are actually using glyphosate as a nutrient source?

Accepted Answer

Measure the decrease in glyphosate concentration in the medium over time

Question 15

What is the Kirby-Bauer test, and why was it used on glyphosate-resistant and sensitive organisms?

Accepted Answer

It is a disk diffusion assay to test antibiotic susceptibility; to compare resistance profiles of organisms exposed to glyphosate

Question 16

Why was a surfactant plate included when screening for glyphosate sensitive/resistant organisms using RoundUp?

Accepted Answer

To control for the effects of surfactant present in RoundUp, which could affect microbial growth independently of glyphosate

Question 17

Can microbes grow in liquid media without visible turbidity? Why or why not?

Accepted Answer

Yes, some microbes may grow as biofilms or at low densities not detectable by turbidity

Question 18

A sample is diluted 1:100, then 1:10, and finally 1:1000. What is the total dilution factor?

Accepted Answer

$$1:1,000,000$$

Question 19

If you plate 0.1 mL of a $$10^{-5}$$ dilution and count 50 colonies, what is the concentration of viable cells in the original sample (in CFU/mL)?

Accepted Answer

$$5 	imes 10$$^{7}$$ CFU/mL

Question 20

You have a stock solution of glyphosate at 10% (w/v). How many mL of this stock would you need to make 500 mL of a 2% (w/v) solution? Use the formula $$C_1V_1 = C_2V_2.$$

Accepted Answer

$$100 mL$$

Microbial Fermentation, Gram Staining, Glyphosate Effects, and Microbial Calculations

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