Micro lab test 2

Each species is characterized by a minimum, maximum, and optimum temperature, collectively known as its____ temperatures.

cardinal

The temperature that promotes the highest growth rate of a given bacterial species is the

optimal growth temperature.

You isolate a pathogen that causes respiratory infections in humans. What temperature(s) would you expect to support its growth?

Any temperature between 20°C and 40°C

Microbes that survive temperatures in the 65°C to 110°C range are considered

extreme thermophiles.

Listeria monocytogenes has a broad temperature range for growth. Select all of the consequences of this point.

It can grow in refrigerated foods.

It can grow in the human body.

It can survive freezing temperatures

what is the best conclusion about mesophiles?

They would not grow at 70°C.

In the experiment effect of temperature on microbial growth, the independent variable is

incubation temperature.

In the experiment effect of temperature on microbial growth, the dependent variable is

culture turbidity.

The organisms most likely to cause frozen food spoilage are (select all that apply)

psychrotrophs.

prokaryotes.

Choose the true statement(s) about a plate with fewer than 30 colonies in the standard plate count laboratory exercise. (Select all that apply.)

-A plate with fewer than 30 colonies is statistically unreliable and is not counted..

-A plate with fewer than 30 colonies is designated as TFTC (too few to count).

The standard plate count method is used to

determine the number of living cells in a sample.

Assume you counted 200 colonies on a plate that was inoculated with 0.01 mL of a sample that was diluted 100-fold. What is the sample's original cell density (OCD)?

2,000,000 CFU/mL

OCD= CFU/ (D × V)

OCD= 200/ (.01 × .01 mL)= 2,000,000 CFU/mL

How many milliliters (mL) is 3,300 μL?

3.3 mL

The best definition of a "countable plate" is

A 100 mm agar plate that contains at least 30 colonies, but no more than 300 colonies

A sample has a density of 1.37 × 105CFU/mL. What sample volume(s) should yield a countable plate? (Select all that apply.)

0.001 mL

0.002 mL

Which of the following is a limitation of the standard plate count method? (Select all that apply.)

This method will not enumerate all bacteria in a sample....

This method can only count bacteria that we can grow in the laboratory setting.

Assume you added 1 mL of a non-diluted sample into 999 mL of water. What is the final dilution?

This is a 1,000-fold dilution.

A visible plaque on a lawn of bacteria grown on a plate indicates

where phage has replicated in bacteria resulting in bacterial lysis.

In the plaque assay of virus titer, the 15-minute pre-absorption period functions to

allow phage to attach to bacterial cells.

If you had a sample with an original phage density of 8.5 × 10^5 PFU/mL, how many plaques would have been observed on a plate of the sample with a dilution factor of 10^-4 mL?

85

In the plaque assay of virus titer, how does the volume of the bacteria used factor into the dilution factor of the phage sample?

It does not factor in since the whole volume of cells is plated.

What is the calculation pf phage titer?

PFU= Volume plated X Dilution

what is a plasmid?

small, usually circular pieces of extra-chromosomal DNA that exist innature in bacteria and yeasts and are sometimes transferred between individuals

what is transformation?

the uptake of exogenous(originating from outside the cell), naked DNA by a cell

Why is naturally occuring transformation benefical to bacteria?

it helps bacteria because they can pick up DNA from dead bacteria around them. This new DNA might give them useful traits, like fighting off antibiotics or surviving better intheir environment. It helps bacteria change and adapt quickly without needing to reproduce

Why is transformation useful to research scientists?

they can put new DNA into bacteria on purpose. The bacteria will then use that DNA to make proteins or show new traits

what are ways to combat the devleopment of antibiotic-resistant bacteria?

only using antibiotics when necessary, completing the full course of antibiotics, avoid overuse of antibiotics in animals, develop new antibiotics and treatments, and use proper infection prevent methods

What would you expect to see if you plated bacteria transformed with antibiotic resistance onto a plate lacking antibodies? Why?

you would see growth of all bacteria. This is because both the cells that were successfully transformed have plasmid and DNA and the cells that were not transformed can grow and survive when no antibiotic is present to kill them.