Lab Final Flashcards
describe a complex culture media…
-exact composition is NOT known
-made from meat and soybean extract
describe a enrichment culture media…
-has extra growth factors to support the organisms with special nutritional needs
describe a differential culture media…
-has pH indicators; allows for different organisms to be distinguished by changing color
describe a selective culture media…
-has special chemicals that stimulate growth of some bacteria while inhibiting the growth of others
spherical shaped bacteria are called
coccus; cocci
rod shaped bacteria are called
bacillus; bacilli
helical & curved bacteria are called
vibrio, spirillum, spirilli, spirochetes
diplo means
there are 2 bacterium
tetrad means
that are 4 bacterium
strepto means
the bacterium is in a line formation
staphylo means
there is a clump/cluster of bacterium
coccobacillus means
the bacterium is oval shaped
vibrio means
the bacterium is curved
spiral means
complete 360 turn
define antiseptic
a chemical agent that is used in association with the skin and mucous membranes to destroy microorganisms or inhibit their growth
define disinfectant
a chemical agent that is used on inanimate objects to destroy microorganisms
define antibiotics
natural, semisynthetic, and synthetic chemicals that inhibit the growth of other microorganisms
define aerobe
cannot grow w/o oxygen
define anaerobe
cannot tolerate oxygen
define facultative anaerobe
prefer to use O2 but when absent will use other alternatives
define a psychrophile
organism with an optimal growth temp. range of -5 degree C to 20 degrees C
cold loving
define mesophiles
organisms with an optimal growth temp. range at 20 degrees C to 50 degrees C
define thermophiles
organisms with an optimal temp. growth range of 50 degrees C to 80 degrees C
define halophiles
bacterium that require higher salt concentrations to grow
define acidophiles
organism with the optimal growth range of pH 5.5 or below
define a alkaliphile
organism with the optimal growth range greater than 8
define an indicator organism
test that ONLY tests for one kind of organism
describe coliforms
- gram negative
- non-endospore forming bacillus
- ferments lactose w/ gas production
- facultative anaerobe
what does MPN stand for?
most probable #
define potable
water that is deemed safe to drink
define transient flora
microorganisms that are acquired from the environment
define resident flora
microorganisms that are always found on the body
define broad spectrum
an agent that exerts an effect against many different organisms
define narrow spectrum
an agent that exerts an effect against only a few organisms
define transformation
the transfer of genes from the environment
what are the steps in gram staining?
crystal violet
grams iodine
95% ethyl alcohol
safranin
in the T-streak procedure and pour plate procedures, why is the loop sterlized?
to reduce the # of cultures in each section of the T-streak, helps to increase the chances of having an isolated culture
Why are agar plates inverted during incubation?
to minimize/prevent the accumulation of condensation which could compromise an isolated culture
what chemical properties influence diffusion into agar
molecular weight
hydrophobicity
volatility
why are zones of inhibition compared to a standard table to determine an organism’s sensitivity?
b/c antibiotics are used internally. Accounts for absorption, digestion, metabolism, and excretion of the antibody in humans/ animals.
ADME
what is the autoclave temperature and pressure?
15 psi
121 degrees Celsius
why is an autoclaved used?
b/c boiling will not remove endospores due to their thick cell walls
in part 1 of coliform testing the presumptive test was done by
inoculating the lactose broth in a Durham tube
part 2 of coliform testing also known as the confirmed test was done by
taking a positive sample and streaking it on EMB
EMB is differential for
lactose fermentation
Lac+ results in
dark red colonies
EMB is selective for
gram-negative bacteria
formula to calculate VC/mL
(# of colonies/ vol. of sample) x dilution factor
The standard plate count is used to determine…
the # of viable bacteria per mm
formula to determine the total magnification
objective * 10X
Oxidase Test
tested for:
positive test:
negative test:
- presence of cytochrome oxidase
- blue color when oxidase reagent is added
- no color change
Catalase Test
tested for:
positive test:
negative test:
- catalase enzyme
- bubbles when peroxide is added
- no change when peroxide is added
what is used for carbohydrate fermentation?
4 tubes
- glucose
- lactose
- sucrose
- mannitol
carbohydrate fermentation produces
acid and/or gas
what is the indicator found in the test tubes for carbohydrate fermentation? what color changes indicate acid and alkaline condition?
phenol red
- acid: yellow
- alkaline: pink
Hemolysis Test
tested for:
positive test:
negative test:
- hemolysin
- zone of clearing
- no zone of clearing
beta-hemolysis indicates
complete clearing of blood around colonies
alpha-hemolysis indicates
partial clearing of blood around colonies
positive result for H2S production is
a black precipitate
what medium is used to determine the production of H2S?
SIM medium
Urea Hydrolysis
tested for:
positive test:
negative test:
- urease
- hot pink
- yellow-orange
yellow-orange is the initial color
- a negative result would be no color change
Coagulase Test
tested for:
positive test:
negative test:
- clotting of plasma
- clot
- no clot
Starch Hydrolysis
tested for:
positive test:
negative test:
- amylase
- zone of clearing after addition of grams iodine
- no zone of clearing
Citrate Test
tested for:
positive test:
negative test:
- citrate
- bright blue
- green
blue at alkaline pH
green at neutral pH
MSA test is selective for ____ and differential for _________.
- halophiles
- mannitol fermentation (yellow)
EMB test is selective for ____ and differential for _________.
- gram negatives
- lactose fermentation
BAP test is differential for
- hemolysins enzymes
describe the effect of elevated temperatures on proteins
they are denatured by any temp. above their maximum growth range
- it is irreversible
- the proteins unfolds an will NEVER return to its original shape
describe the effect on organisms in temperatures below the minimum growth range
-proteins are not denatured but the enzymes do NOT work properly
-the cells survive but CANNOT grow and reproduce
a too acidic or too alkaline pH causes…
irreversible protein denaturation and cell death
in hypertonic solutions bacteria will
shrivel and die
in hypotonic solutions bacteria will
expand and eventually explode
name a facultative halophile
Staphylococcus epidermidis
when exposed to UV radiation which organism, S. epi or B. meg, survived the longest? why?
B. meg
- b/c it forms endospores which have thick cell walls that UV light can NOT penetrate
which molecule is the target of UV light? How is the damage actually caused?
thymine in DNA
by causing adjacent thymines to interact with one another, forming covalent bonds and creating thymine dimers
What are some sources of error that can occur with the filter-paper disk method?
- deeply inserting disks
- varying amounts of bacterium on plate
- not having a round disk
- measuring zones of inhibition
What are some chemical properties that can effect the filter-paper disk method?
- hydrophobicity
- volatility
- mw
what media was used in the Kirby-Bauer experiment?
MHA
penicillin’s mode of action is to..
inhibit cell wall synthesis
SxT’s mode of action is to…
inhibit the metabolic pathways
polymyxin B mode of action is to..
disrupt the cytoplasmic membrane
nalidixic acid mode of action is to..
inhibit nucleic acid synthesis
tetracyclines mode of action is to…
inhibit protein synthesis
gram reaction & morphology of E. coli
- gram-negative
- coccobacillus
gram reaction & morphology of salmonella
- gram negative
- bacilli
gram reaction & morphology of proteus
- gram negative
- bacilli
gram reaction & morphology of pseudomonas
- gram-negative
- bacillus
which organism ferments lactose?
e. coli
which organism is urease-positive?
proteus
which organism is oxidase-positive
pseudomonas
which organism ferments neither glucose or lactose?
salmonella
Streptococcus
gram reaction
morphology
arrangement
- gram-positive
- cocci
- strepto (line)
Staphylococcus
gram reaction
morphology
arrangement
- gram-positive
- cocci
- staphylo (cluster)
Describe the physiological characteristics of Staphylococcus aureus
- beta hemolysis
- ferments mannitol
- positive for coagulase production
what organism was used for the bacterial transformation lab?
Acinetobacter calcoaceticus
what is streptomycin’s mode of action?
to inhibit translation
what is bacterial transformation
the transfer of genes from the environment
