Microbio Lab Exam 1

A disinfectant is used on your work surface…

before and after lab, after any spills

T/F: Beverages are allowed in the lab as long as the containers are covered

false

T/F: You may eat a snack in lab as long as there are no bacterial cultures o your bench and you have thoroughly washed your hands

false

The best source of information regarding the hazards posed by any chemical and specific handling instructions is the ________

material safety data sheet (MSDS)

T/F: Paper towels should be discarded in a biohazard container after washing hands

false

Which of the following items may be on the lab bench top while doing lab work?

\
cultures

equipment needed to complete lab activity

backpack/purse

pencil/pen

cell phone

cultures, equipment, pencil/pen

Where do you dispose of a swab used to culture your throat during lab?

biohazard bag

When is food and/or beverage allowed in the lab?

never

What are the steps of hand washing?

wet hands, apply soap, lather for at least 20 seconds, rinse, dry

Jackie went to the sink at the end of lab to wash her hands.  After removing her watch and rings, she turned on the water, wet her hands, added soap and thoroughly rubbed and lathered her hands for 30 seconds, cleaning the backs of her hands, her fingernails, and between her fingers. She then turned off the water,  and reached for the paper towels to dry her hands. What did Jackie do wrong?

Jackie should have used paper towels to turn off the faucet

T/F: Using a cell phone in lab is permissible since it can be used for timing experiments

false

Where should you dispose of cultures on agar plates?

biohazard bag/bin

T/F: Thoroughly washing hands will sterilize them

false

How long should the hands be lathered with soap and water?

20 seconds

Which hand-washing step will prevent the immediate recontamination of the hands after washing?

turning faucet off with paper towel

When should soap be added to the hands?

after hands are wet

T/F: If gloves are worn in lab, hand washing is unnecessary

false

Jacob had just finished his lab work and went to the sink to wash his hands.   He removed his watch, and added liquid soap to his hands.  He then turned on the water and began to rub his hands together, lathering for 20 seconds and cleaning fronts and backs of hands, fingernails, and between his fingers.  He then rinsed his hands in running water,  dried his hands with paper towels, and used an additional paper towel to turn off the faucet. What did Jacob do wrong?

Jacob should have wet his hands before applying soap

What items should be put away before entering the lab room?

phone, water bottle, headphones

Which waste container do discarded cultures and used gloves belong in?

biohazard waste

What would be considered inappropriate clothing for being in lab?

flip flops, hats, shorts

When should hands be washed?

after contact with any potentially hazardous material, after lab, after removing gloves

Describe procedure to clean biohazard spills

notify instructor, place paper towels over spill, soak towels with disinfectant, let sit for designated contact time, wipe up and dispose of towels in biohazard waste

Why do safety rules exist for lab?

prevent sicknesses, contamination, accidents, transfer of microbes outside lab

What resources should you use if you have questions/concerns about safety in lab?

instructor, MSDS, biosafety occupational health program

T/F: Under certain circumstances a person’s resident biota can act as opportunistic pathogens

true

The identities of microorganisms on our planet are still mostly _______

unknown

Microbes are found in…

earth’s crust, human body, oceans

T/F: Reservoirs are always humans or other animals

false

Microorganisms are found in nearly every environment and are said to be ________

ubiquitous

Partial lysis of the red blood cells surrounding a bacterial colony indicate that the colony is _____ hemolytic

alpha

Microorganisms are not likely to be found on _______ objects

sterile

The beta-hemolysis of blood agar observed with Streptococcus pyogenes is due to the presence of _______

streptolysin

Opportunistic pathogens cause disease in __________ individuals

compromised

A saprobe derive nutrients from _______ plants and animals while a parasite derives nutrients from ________ plants and animals

dead; living

T/F: There are many different sterile environments on Earth

false

T/F: Swabbing the surface of your skin anywhere on your body and culturing that sample in lab is likely to result in growth of millions of bacterial cells on the culture plate, even if you practice good hygiene

true

Microorganisms that live in or on the human body are called the ____

microbiome

T/F: Only 2 of the main types of microorganisms are found in or on the normal healthy human body

false

Microorganisms have adapted to nearly every environment through the process of ________

evolution

Most of the time, microbes in natural circumstances exist in relationship with ________

other species

Colonies that do not affect the red blood cells int he surrounding medium are ________ hemolytic

gamma

T/F: Most microorganisms that are found in and on humans do not cause harm and can sometimes benefit the host

true

The primary, natural habitat of a pathogen where it continues to exist is called the _______

reservoir

Disease-causing microorganisms are called _______

pathogens

When microbes are in a close nutritional relationship and one benefits but the other is not harmed is called ________

commensalism

A common medium for culturing fastidious bacteria is _________

blood agar

Being completely free of all life forms, including spores and viruses is referred to as _______

sterile

_______ applies to living tissues; ________ applies to inanimate surfaces

antisepsis; disinfection

_________ is the introduction of unwanted microorganisms

contamination

T/F: Aseptic technique is used only in the microbiology lab environment

false

Where should the label be placed on petri dishes?

on the bottom

T/F: Petri dishes should be incubated with the lid side up

false

What would indicate an unsuccessful aseptic technique?

no growth, different colored colonies on slant, fungal growth in original broth culture

An inoculating loop/needle is sterilized by holding it in the ________ part of the Bunsen burner flame until _______

hottest; red-hot

What agents will kill a microbial pathogen or completely inactivate its ability to cause disease?

virucide, germicide, sporicide

Microbial control methods that kill ________ are able to sterilize

endospores

The minimum sterilizing conditions in a steam autoclave are ____ at ____ psi for _______ minutes

121 degrees C; 15; 15

________ is the destruction of most microbial life on inanimate surfaces

disinfection

_______ is the destruction of all microbial life

sterilization

________ is the destruction of most microbial life on living tissue

antisepsis

________ is the mechanical removal of most microbes from living or inanimate surfaces

decontamination

The best medium for observance of macroscopic growth is the ______

agar plate

Which observations can be made when observing growth on nutrient agar?

amount, opacity/clarity, and color of colonies

The _______ plate method involves spreading an inoculum in some areas of the plate after incubation, whereas the _______ plate method involves diluting an inoculum into several melted agar tubes and then adding their contents into plates for solidification and incubation

streak; pour

What are the 5 I’s?

inoculation, incubation, isolation, inspection, identification

What’s the term for a culture made from one isolated colony?

axenic or pure

A microbiologist inoculates *Staphylococcus aureus* into a culture medium. Following incubation, both *Staphylococcus aureus* and *Staphylococcus epidermidis* are determined to be growing in this culture. What is the most likely explanation?

culture was contaminated

What’s the purpose of streaking for individual colonies?

obtain isolated colonies

When using streak plate technique how often is it necessary to sterilize your loop?

before, between and after streaks

What would cause equal growth in each quadrant?

loop not sterilized between quadrants

A pure culture contains __________ bacterial species

a single

What would result from obtaining a culture sample before streaking every quadrant?

no single colonies, all quadrants would look the same

What would result from not sterilizing the loop between each quadrant?

quadrants look the same

What would result from not drawing your loop through the previous quadrant?

growth only in quadrant 1

What would result from sterilizing your loop after obtaining a culture sample but before streaking your plate?

no growth

What’s the purpose of heat fixing?

adhere bacterial cells to slide and kill bacterial cells

The benefit of using a differential stain is it allows microbiologists to determine _________

differences between organisms or parts of the same organism

Why may a Gram stain not yield clear results?

poor technique, age of culture, too thick emulsion

What are the steps for Gram stain procedure?

emulsion, heat fix, crystal violet for 1 min, rinse, iodine for 1 minute, rinse, rinse with alcohol till runoff is clear, rinse, safranin for 1 minute, rinse, blot dry

What happens if iodine is not added to Gram-positive cells?

cells appear reddish/pink

What happens if no decolorizer is added to Gram-negative cells?

cells appear purple

What happens if safranin is not added to Gram-negative and Gram-positive cells?

cells are purple or colorless

What happens if crystal violet and safranin steps were reversed on Gram-negative and Gram-positive cells?

cells appear purple

What’s the purpose of the mordant?

enhance crystal violet staining by forming crystal violet-iodine complex

You performed a Gram stain and are expecting to find purple Gram-positive bacilli and reddish/pink Gram-negative cocci. Instead, you observe both purple bacilli and purple cocci evenly distributed on the slide. How would you best explain this?

sample was under-decolorized

Agar is an important component of media because agar provides _______ for bacterial growth

a solid surface

Which method often results in colonies developing down throughout the agar along with some colonies on the surface?

pour plate

T/F: The terms “sterile” and “pure” can be used interchangeably when discussing cultures, because they both refer to a culture that has not been contaminated

false

Which isolation technique is most effective for the majority of applications and is most commonly used for colony isolation in the lab?

streak plate

A ______ is a mound of cells on a solid medium that represents the progeny from one original bacterial cell

colony

When preparing pure cultures, dilution is necessary for _______ the number of inoculated organisms so that _______ colonies can develop

reducing; isolated

________ is a second-level culture where an isolated colony from one culture is taken and transferred into a new medium

subculture

The purpose of staining cells on a microscope slide is to _______ to see them better

add contrast

________ refers to the microscope’s ability to show 2 separate objects as discrete and distinct

resolution

Mordant is ________, primary stain is _______, counterstain is _______, and decolorizer is _______

iodine; crystal violet; safranin; alcohol

Basic dyes are attracted to _______ surface of bacterial cells

acidic

A microbiologist makes a fixed smear of bacterial cells and stains it with methylene blue. All cells appear blue under the oil immersion lens. This is an example of ______.

simple staining

_______ of the microscope magnifies the specimen to product the virtual image of the specimen

ocular lens

Cells of *Staphylococcus aureus* are cocci measuring about 1 μm in diameter. In a textbook image of *S. aureus*, each cell measures about 1 cm. The magnification of the image on the page is ______

10,000 (6 -2 = 4 0s)