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why can microbes be found everywhere
they can metabolize many substrates, they require small amounts of nutrients, and they can tolerate a broad range of environments
why is swabbing the bottom of your shoe considered a positive control
there is 100% probability of microbes on your shoe
why do cotton swabs collect more bacteria when theyre wet
the water allows for more microbes to stick to the swab and better represents the microbes that are found in that location
why do you need to move the otton swab back and forth multiple times whencollecting samples
to ensure that as many microbes as possible will be collected and deposited on the plate
why dont we find viruses when we plate our samples
because viruses need a host to live
how do you decide what temperature to incubate the sample in
in the temperature the sample came from
what is colony morphology
a description of what a single colony looks like growing on a plate
why is colony morphology impotant
it is essential in determining the identity of the microbe
what characteristics should be included when describing colony morphology
size, color, texture, shape, elevation, and margin
what are three distinct characteristics to fungal colonies
fuzzy, large, and multicolored
whare are three characteristics that are distinct to bacterial colonies
smooth, small, and single color
words to decribe shape
circular, irregular, filamentous, or rhizoid
terms to describe elevation
raised, convex, flat, umbonate, crateriform
terms to describe margin
entire, undulate, filiform, curled, and lobate
terms to describe texture
smooth, dry, mucoid, or fuzzy
what type of stain is used for a simple stain
basic stain
how do basic stains work
they are positively charged so they can easily bind to bacteria since bacteria are negatively charged
why would you use a simple stain
to determine cell morphology, arrangement, and size
what are three things heat fixing does for your bacterial smear
makes bacteria stick to the slide, kills them so they are not moving around, and also makes them more visible by coagulating cellular proteins
how is cell morphology different than colony morphology
cell morphology describes a singular cell while colony morphology describes a colony of cells
what are the different shapes of bacteria
coccus, bacillus, and coccobacilli
what are the different arrangements of bacteria
staphylo and strepto
what are some advantages for microbes living in aquatic environments
there is plenty of nutrients and limited competition
why are bacteria and fungi mainly studied in this lab
they are everywhere, easy to grow, and big enough to see growing in a media
why can you look at photosynthetic microbes without stain
because they are colorful from they’re photosynthetic pigments
how are protozoa different than cyanobacteria
they are larger and very motile
how algae bencifical to a pond
they are the base food for the food web
how are algae harmful to a pond
in large number’s they can release a toxin into the water that is dangerous to animals
what type of stain is used for a negative stain
acidic stains
how does a acidic stain work
they have a negative charge and since bacteria also have a negative charge they will repel the stain and only the background will be colored
why would you use a negative stain
to record the true size of bacteria and some bacteria can fall apart when heat fixed ruining the slide
what would happen if you heat fixed a negative stain
heat fixing could cause the bacteria to fall a part and ruin the true size of the bacteria
why do you get to use a lot of bacteria on a negative stain
because the large amount of bacteria will be spread over the entire slide with a another slide
why is serial dilutions needed for standard plate count
if you didn’t the entire plate would be covered with bacteria and you wouldn’t be able to count the individual colonies
do you have to start with a pure culture to perform a standard plate count
no
provide three examples of when someone would want to know how much bacteria was in a sample
bacteria in food, in water, in a hospital
why is it important to keep track of the amounts of bacteria you are moving during serial dilutions
to be able to calculate how many bacteria were in the orginal sample
why is it important to change tips while performing serial dilutions
so extra bacteria is not transferred into the tube
why does it matter if you use a sterile diluent when performing serial dilutions
so they is not bacteria in the water
why is mixing tubes important when performing serial dilutions
so the bacteria are evenly distributed throughout the tube so when pipetted an even distribution of bacteria are sucked into the pipette
what is a gram stain
a complex differential stain through a series of staining and decolorization steps will differentiate bacteria based on their cell wall composition
what information does gram stain tell you
if the bacteria gram positive or gram negative
what cell characteristic does the gram stain differentiate
how much peptidoglycan is in the cell wall
what color is a gram negative cell
pink
what color is a gram positive cell
purple
do gram positive cells have a lot or little peptidoglycan in their cell wall
a lot
do gram negative cells have a lot or a little peptidoglycan in their cell wall
a little
what is the primary stain in gram stain
crystal violet
what is the role of crystal violet
to stain all the bacteria purple
what is the mordant in a gram stain
iodine
what is iodine’s role in gram stain
to form a complex with the crystal violet in the cells that have a lot of peptidoglycan
what is the decolorizing agent in gram stain
gram’s alcohol
what is the role of gram’s alcohol in gram stain
to remove crystal violet from the gram negative cells because they did not form a complex with the iodine and can be easily removed.
what is the counter stain in gram stain
safranin
what is the role of safranin
to stain the gram negative cell pink
what happens if you use too many bacteria in your smear for gram stain
you could have a false positive gram positive stain
why are the timings important for gram stain
so the bacteria o not become over stained or under stains making the results unreliable
why are gram controls used
to tell if your stain was accurate or not
what is the purpose of streaking for isolation
to have an isolated colony
why is streaking for isolation commonly done with environmental samples
to identify the bacteria in the environmental sample
why is it important to have isolated colonies to work worth
so tests can be performed to determine what kind of bacteria is present
what are the two ways to streak for isolation
new school method and trident method
do you think you would get isolated colonies if you forgot to sterilize your loop using streaking for isolation methods
no because bacteria would remain on the loop and the number of bacteria would be hard to diminish enough to get an isolated colony
what are aseptic techniques
method to prevent contamination
examples of aseptic techniques used in lab
not leaving things open, sterilizing the loop, working close to the flame, briefly swiping the lip of the vessel through the flame, and being efficient.
what could happen id you are not aseptic in lab
could end up not having a pure culture
what are the two types of solid media we use in micro lab
agar plates and agar slants
what is the type of liquid media we use in lab
broth culture
what is general media
energy sources such as tryptic soy agar (TSA) and tryptic say broth (TSB)
what is the purpose of autoclaving media before using it
to sterilize the media
what do you do when you inoculate the agar
put bacteria on it
what is a pure culture
a singular type of bacteria
why do we use a zig zag streak
just to spread the bacteria since we are not trying to isoable it
what information should be included when labeling plates
name, date, name of sample, and what type of media it is if it is something other than TSA or TSB
why do you label the bottom of the plates
incase the lid falls off and gets mixed up
why do we incubate plates lid side down
it prevents any liquid on the lid from dripping onto the agar
how does UV light kill bacteria
by breaking double stranded DNA
how do we take advantage of using UV light
to disinfect workspaces, hospitals, and tools
what is the disadvantage of using UV light
UV light can not penetrate any material
does UV light sterilize objects
no only disinfects them because to be able to sterilize an object the object must be isolated from the air and since UV light is incapable of getting through whatever you surround the object with it can not sterilize it
how long does it take to kill microbes with UV light
40 seconds
what is selective media
media that contains ingredients that prevent certain types of bacteria from growing
what is differential media
media that contains ingredeints that show different characteristics of bacteria
how are mannitol plates selective
they have a high NaCl concentration so only gram-positive staphylococci can grow in them
how are mannitol plate differential
if the bacteria can ferment mannitol it will change the color of the plate to a yellow
how can mannitol plates tell us if bacteria is pathogenic
because only pathogens can ferment manitol
starting color of mannitol salt agar
red
color of mannitol salt plate with a non pathogenic gram-positive staphylococci bacteria
maroony red
color of a mannitol plate with bacteria that can ferment mannitol
yellow
how are macconkey selective
bile salts and dyes inhibit the growth of gram-positive bacteria
how are macconkey differential
can differentiate between lactose fermenters and non fermenters based on color change
starting color of macconkey agar plates
yellow
what color are macconkey agar plates with bacteria that can ferment lactose
pink
how are eosin methylene blue agar plates selective
dyes in the media prevent gram positive bacteria from growing
how are eosin methylene blue agar plates differential
if bacteria can ferment lactose is will change the pH of the plate and cause a color change
how are eosin methylene blue agar plates semi-quantitative
depending on the amount of lactose fermented different colors of colonies will grow on the plate
what is the starting color of eosin methylene blue agar plates
a dark red/purple
what color is an eosin methylene blue agar plate with bacteria that ferment low levels of lactose
light pink/purple colonies
what color is an eosin methylene blue agar plate with bacteria that ferment high levels of lactose
black or metallic green on the bacterial growth
what color is an eosin methylene blue agar plate with bacteria that ferment medium levels of lactose
darker pink/purple colonies
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