Micro homework questions

Match with either Sterilization or Disinfection: Autoclave

sterilization

Match with either Sterilization or Disinfection: Kills all microorganisms on a surface

sterilization

Match with either Sterilization or Disinfection: Kills many microorganisms on a surface

disinfection

Match with either Sterilization or Disinfection: Bleach

disinfection

Match it correctly with either Streak Plate or Spread Plate: Goal is to determine original CFU/mL

spread plate

Match it correctly with either Streak Plate or Spread Plate: Goal is to generate pure culture

streak plate

Match it correctly with either Streak Plate or Spread Plate: Perform a dilution series in order to obtain desired amount of colonies on the plate

spread plate

Match it correctly with either Streak Plate or Spread Plate: Dilutes cells by mechanical separation on the media

streak plate

Why is it important to allow a sterilized inoculating loop to cool before attempting to sample liquid culture? 

To avoid creating aerosals

Why does immersion oil improve the resolving power of the 100X objective? 

Light diffracted by the specimen is directed into the 100X objective by immersion oil

T/F Characteristic of a positive/negative stain: It colors the background, leaving the bacterial cells clear or white.

false

T/F Characteristic of a positive/negative stain: It is a differential stain because it stains cells differently than negative stains.

false

T/F Characteristic of a positive/negative stain: It stains all cells the same time

true

T/F Characteristic of a positive/negative stain: It is positively charged and binds to the bacterial cell wall

true

T/F Why is it necessary to stain bacterial cells in order to view them using brightfield microscopy? Staining is necessary in order to fix cells to the slide

false

T/F Why is it necessary to stain bacterial cells in order to view them using brightfield microscopy? Since the bacterial cells are mostly water, they do not absorb much light

true

T/F Why is it necessary to stain bacterial cells in order to view them using brightfield microscopy? Staining makes the cells more visible by increasing the contrast between the cell and the background

true

What should you do when you first pick up your inoculating loop? 

Flame sterilize it from stem to loop

If you have immersion oil on your slide, which objective should you use? 

100x

For Gram negative rods, how would the cells appear after the following steps of a Gram stain?  Iodine

purple

For Gram negative rods, how would the cells appear after the following steps of a Gram stain? Safranin

pink

For Gram negative rods, how would the cells appear after the following steps of a Gram stain?  Crystal violet

purple

For Gram negative rods, how would the cells appear after the following steps of a Gram stain? Ethanol

colorless

Bacterial cultures used for Capsule Stain are typically grown in milk based culture broths. Why? 

Milk supplies the required carbohydrates

Lack of heat-fixing during Negative Staining is both an advantage and a disadvantage. How is lack of heat-fixing an advantage? 

Less distortion of the cell's size and shape

Which type of stain utilizes both positive and negative stains? 

capsule stain

The ______ stains are able to directly bind to bacterial while the background remains unstained, while ______ stains are repelled away from bacterial cells, but background is strained the color. 

positive/negative

elect simple or differential stain for each method: Gram stain

differential

elect simple or differential stain for each method: Spore stain

differential

elect simple or differential stain for each method: Negative stain

simple

elect simple or differential stain for each method: Staining with just crystal violet

simple

What is the appropriate mordant for each type of stain: Spore Stain

heat

What is the appropriate mordant for each type of stain: Gram Stain

iodine

What is the appropriate mordant for each type of stain: Capsule Stain

none

Which staining method used in MCB101 cannot be heat-fixed? 

capsule stain

Select the correct decolorizer for each type of staining: Negative Stain

none

Select the correct decolorizer for each type of staining: Gram Stain

95% ethanol

Select the correct decolorizer for each type of staining: Acid Fast Stain

acid alcohol

Select the correct decolorizer for each type of staining: Spore Stain

water

Types of symbiosis: A bacterium that normally resides in the human respiratory tract that has overgrown and is now causing disease

parasitism

Type of symbiosis: A bacterium the lives in the human small bowel that consumes negligble amounts of nutrients while secreting vitamins absorbed by its host

mutalism

Types of symbiosis: A bacterium that secretes a toxin causing diarrhea

parasitism

Type of symbiosis: A bacterium that is found on the skin and derives nutrients from dead skin cells

commensalism

A 68 year old woman is given a two week course of antibiotics to treat an infected tooth. Shortly after completing the first week of antibiotics, she develops persistent diarrhea that does not resolve for 3 weeks. How might use of antibiotics have contributed to the development of diarrhea in this woman? 

Reduction of microbial diversity allows an opportunistic pathogen to overgrow

70% ethanol is the most effective concentration of ethanol for disinfection. Why? 

It acts slow enough that it can effect the entire bacterial cell.

Sterilization and/or disinfection: Kills all microorganisms present on a surface

sterilization

Sterilization and/or disinfection: Requires a defined exposure time in order to function

sterilization and disinfection

Sterilization and/or disinfection: Only reduces the number of microorganisms present on a surface

disinfection

T/F of the methods of sanitization and sterilization that works under room temperature: Detergent

true

T/F of the methods of sanitization and sterilization that works under room temperature: Autoclave

false

T/F of the methods of sanitization and sterilization that works under room temperature: Boiling

false

T/F of the methods of sanitization and sterilization that works under room temperature: Chlorine/Bleach

true

When autoclaving for sterilization, the autoclave must reach ____________ under ______________psi pressure. 

121°/15

Bacteria tend to be able to persist on most surfaces for ____? 

months

Enveloped viruses tend to persist on most surfaces for only ______? 

hours

How will you inoculate your RODAC plate? 

Gently pressing it against a flat, dry surface

What is the minimum number of colonies on a RODAC plate to consider a surface unsatisfactorily sanitized? 

21

What is the contact time in minutes for disinfection of a surface with Lifegaurd?  Note: this is the disinfectant that we use in the MCB 101 lab, found in student spray bottles on the pyramids. 

10 mins

Which type of media used during this lab exercise is specially formulated to grow lactic acid producing bacteria? 

MRS Media

What is the source of bacteria for the cabbage fermentation exercise? 

The cabbage is naturally colonized by lactic acid bacteria

What actions are taken during the cabbage fermentation exercise to limit the growth of fungi? 

none

T/F: The regeneration of NADH from NAD+ is the primary goal of fermentation. 

False

What is the main mechanism by which humans utilize bacterial fermentation to preserve food? 

The generation of a non-hospitable environment by useful bacteria that will not support growth of many pathogenic organisms

T/F: Fermentation of cabbage to sauerkraut utilizes various bacteria and fungi already present on the plant as it grows. 

true

What properties of MRS media make it ideal for the growth of Lactobacillus. 

Tween 80 enhances nutrient uptake and extra magnesium allows for the function of key metabolic enzymes

Per the general formula (not simplified) for glycolysis in the manual, there is a required input of _________and generates a output of______________. 

2 ATP and 2 NAD+/4 ATP and 2 NADH

What is the final electron acceptor in fermentation pathways? 

an organic molecule

Electron transport driven by a difference in proton concentration across a membrane allows for the regeneration of NAD+ in fermenting bacteria. 

false

What is the product of homolactic fermentation? 

lactate

What is the main difference between homolactic and heterolactic fermentation? 

Heterolactic fermentation produces byproducts other than lactate

What products produced by heterolactic fermentation inhibit the growth of undesirable microorganisms in the fermentation of cabbage to sauerkraut? 

Lactic acid, ethanol, and sometimes acetic acid

You find an old sample of cabbage fermentation liquid in the refrigerator and you notice that the sample has a foul odor. You inoculate litmus milk with 100 uL of sample to test for contaminants. After 48 hours, you observe the litmus milk and notice a curd has formed but has broken up into a lot of tiny pieces. You recall that this presentation is referred to as "stormy fermentation." What is the most likely contaminant in the fermentation liquid?

Clostridium