Microlab Exam 1

Which technique allowed us to view living microbes as they moved around?

wet mount in bright field, wet mount in dark field, hanging drop technique

During lab, how did you create enough contrast to view living, unstained yeast and bacteria in a hanging drop?

closed the iris diaphragm on the microscope. This adjustment created enough contrast to see yeast cells without any stains

results of stab test with non-motile organism

organism stayed at the stab line

results of stab test with motile organism

organism moved away from stab line and spread throughout the tube

which type of media contains no agar?

broth media 

Why is agar added to certain types of microbial media?

to solidify media

obligate aerobes

require oxygen for survival

obligate anaerobes

die in the presence of oxygen

facultative anaerobes

can grow in the presence or absence of oxygen

psychro-

cold in relation to the middle of the range

thermo

hot in relation to the middle of the range

meso

middle

mesophiles

survive in the middle of the temperature range that supports microbial life

halo-

salt / salinity

halotolerant

can grow in a wide range of salt concentrations

the results of an agar deep stab are below. Since this microbe grew along the entire stab line, it is considered a:

facultative anaerobe

Based on the results shown below, Microbe X is an extreme _____. It only grows in high concentrations of sodium chloride (salt)

halophile

As shown in the table, Staphylococcus aureus is _____. This term means S. aureus can grow in a wide range of sodium chloride concentrations

halotolerant

the _____ technique is used to embed bacterial colonies throughout plate media. To perform this technique, liquified agar plate media is swirled together with the test sample.

pour plate

_____ occurs when two organisms work together to do something that neither one can do alone

synergism

_____ occurs when one organism benefits from another organism. (The other organism is not affected in a positive or negative manner)

commensalism

antibiosis means _____

one organisms harms another

during lab, a student _____ a tube of nutrient broth when they accidentally sneezed into it

contaminated

during lab, a student _____ a tube of nutrient broth when they intentionally added Staphylococcus epidermis to it

inoculated

what’s the proper way to sterilize metal inoculation loops and needles during lab

hold the end of the tool in a flame until it glows red. Once it cools down, it is ready for use

what’s the proper way to sterilize a bacterial spreader

dip the end of the tool in ethanol. QUICKLY pass the end of the tool through a flame. By the time the ethanol burns off, the tool is ready for use

which part of a Petri dish should be labeled with your initials and pertinent info about the experiment

bottom/base of plate (the part that holds the agar medium)

which technique is used to inoculate agar slant tubes

zig-zag inoculation

which technique produces a solid layer of bacteria on the surface of plate media? A sterile swab is used to inoculate the plate

lawn plate

which plating technique is this?

streak plate

True or False: drinks and food are allowed in microbiology laboratories

false

as shown: a _____ is a visible clump of bacterial cells. the cells within this structure arose through binary fission, so they are all genetically identical

colony

Which plating technique is this? Colonies are evenly distributed across the surface of plate media

spread plate

To prevent condensation from dripping onto your plate cultures, it’s best to incubate Petri dishes in this position

upside down (lid underneath the agar medium)

before leaving microbiology lab for the day, you should _____

disinfect your work surface

dispose of your nitrile gloves

wash your hands

you’re instructed to spot inoculate E. coli broth culture on two separate plates. How is this accomplished aseptically?

You should always flame the loop (aka sterilize the loop) between inoculations

part labeled 1

ocular lens

part labeled 2

nosepiece

part labeled 3

objective lens

part labeled 4

stage

part labeled 5

light source

part labeled 6

course adjustment knob

immersion oil is only used with the _____ objective lens

100x

which objective lens gets blurry when it’s accidentally dipped into immersion oil? We skip this objective when refocusing oily slides

40x

what is the total magnification of a microscope when the 10x ocular lenses are used in conjunction with the 4x objective lens?

40x

what is the total magnification of a microscope when the 10x ocular lenses are used in conjunction with the 10x objective lens

100x

bacillus

rod-shaped

coccus

spherical/round shape

strepto-

chains

staphylo-

clusters

diplo-

pairs

which shape and arrangement is this bacteria?

staphylococcus

which shape and arrangement is this bacteria?

streptobacilli

what shape and arrangement is this bacteria?

streptococcus

what shape and arrangement is this bacteria?

diplococci

What is the purpose of heat-fixing certain bacterial smears

heat dehydrates cells and helps them adhere to glass slides

which plating technique is this? Liquefied agar medium is swirled together with a specific volume of the test sample. Following incubation, colonies are embedded throughout the plate medium

pour plate

following the Gram stain procedure, Gram-negative bacteria are _____ in color

pink

following the Gram stain procedure, Gram-positive bacteria are _____ in color

purple

why is 10 minutes of steaming required for certain staining techniques

steam drives stains into hard-to-stain structures, such as spores and the waxy cell walls of acid-fast bacteria

Which tool is used to stab inoculate motility media

metal inoculation needle

two methods we used to test oxygen requirements of different microbes

agar deep stab and anaerobic jar

we observed antibiosis in lab when:

Bacillus subtilis secreted the antibiotic bacitracin. This inhibited growth of Micrococcus luteus, a yellow Gram positive bacterial species

we observed synergism in lab when:

the WF (white) and OF (orange) mutant strains of Serratia marcescens worked together to make a red pigment (prodigiosin) that neither can make alone

we observed commensalism in lab when:

Clostridium (an obligate anaerobe) was able to grow in an aerobic environment when Staphylococcus epidermis was present

antiseptics

reduce the number of microbes on living tissues

disinfectants

reduce the number of microbes on inanimate surfaces

proper way to sterilize forceps in lab

dip the end of the tool in ethanol. QUICKLY pass the end of the tool through a flame. By the time the ethanol burns off, the tool is ready for use.