UMHB Microbiology Lab FInal

The two terms describe the movement of bacteria based on the rotation direction of their flagella ______

and _______.

Running and tumbling

You are looking at pond water with a 40x objective lens and see roundish green things. You conclude they are what?

Algae

Give at least two reasons why microbes are often hard to see in wet preparations(living samples)

- Motile bacteria move very quickly

- They are not stained which makes them hard to see

Name four different structures that cells can use for motility

-flagella

- fimbriae

- pili

- axial filaments

How can flagella enhance a bacterium's virulence?

Flagella allows them to move away from phagocyte's and harmful chemicals, and flagella allow them to move around and spread quickly

amphitrichous flagella

flagella at both ends(ambidextrous)

What is a pure culture of bacteria?

a culture consisting of only 1 bacterial species

Why mixed cultures are of little use in studying microorganisms?

Because they are so close together it is hard to identify specific structures

Why would pour plate technique be used instead of the streak plate method to obtain colonies?

Because the colony growth is restricted by being embedded into the agar

Why is MacConkey agar considered both a selective and a differential medium?

- It is selective because gram + does not grow, while it promotes gram - bacteria

- It is differential because it has a difference in reaction depending on what the color changes. Between the lactose fermenter and the non-lactose fermenter

What two components make MacConkey's agar a differential medium?

Neutral Red and Lactose

What two components make MacConkey's agar a selective medium?

Bile salts and crystal violet

What is tge purpose of NaCL in MacConkey's agar

maintain osmotic pressure

If you want to pipette 100 uL with a micropipetter, how many milliliters are you pipetting?

.1

What does CFU stand for?

colony forming unit

______ Is an example of a direct method of estimating bacterial concentration whereas ________ is an example of an indirect method of estimating bacterial concentration

MPN, Turbidity

Write 100,000,000 in exponential notation

10^8

If you transferred 1 ml of a bacterial culture to tube #1 which contained 9 ml of water, and then 1 ml from tube #1 to tube #2 which contained 9 ml of water, what was the final dilution of the bacteria in tube #1? In tube #2?

1 x 10^-1, 1 x 10^-2

What is the scientific term for cloudiness observed in high-concentration bacterial cultures and what machine can be used to measure it?

Turbidity, spectrophotometer

Why do you dilute the bacterial sample before plating for bacterial counts?

So you can see individual colonies instead of big groups of bacteria

Describe the oxygen requirements and preferences of a facultative anaerobe

They can live both with and without oxygen, but a facultative anaerobe grows better with oxygen

Why obligate anaerobes cannot tolerate oxygen?

they do not have the enzyme catalase to destroy toxic oxygen

What is the optimal growth temperature of meophiles

37 degrees Celsius

What is the definition of TDP

Thermal Death Point - the lowest temperature at which all microbes are killed within 10 minutes in a liquid culture

How do cold temperatures slow the growth of most microbes?

they slow down the growth of most microbes

Salt and sugar increase the osmotic pressure by generating ____ -tonic conditions leading into bacterial death by ______

hyper, plasmolysis

The effectiveness of disinfectants is commonly tested against 3 main classes of microorganisms by the industry. What are the three classes of microorganisms?

- Gram +

- Gram -

- Viruses

What is the difference between disinfectants and antiseptics

-Disinfectants are for nonliving surfaces to get rid of microbes

- Antiseptics are to clean living tissue of microbes

Bactericidal

kill microbes directly

bacteriostatic agent

an agent that inhibits the growth of bacteria

What is the sequence of events that leads into cellular damage by UV lights

Thymine dimers -> Mutation -> apoptosis

What is one drawback of using UV light for sterilization?

It cannot penetrate

What is the most important thing to do when using disinfectants for cleaning

Read the directions