lab practical 1 Flashcards
what does emb select for and if its e. coli what color will it turn
colliforms
metallic green for e coli
acid-fast will be what two colors
blue and pink
in acid fast staining:
light blue is what
pink is what
non acid fast acid fast (mycobacterium)
gram positive is what color
purple/blueish
gram negative is what color
pink/reddish
what is the purpose of a streak plate
dilute bacteria to get a single CFU (colony forming unit)
parts of gram staining
primary stain- crystal violet
mordant- iodine
decolorization-ethanol
counterstain- safranin
shapes of bacteria
bacilli (rod)
cocci (ball)
spirilla (spiral)
arrangements of bacteria
cluster
chain
what is a gram reaction
whether it is gram + or gram -
selective media definition
selective media selects for a desired trait
ex: antibiotic resistance
differential media definition
used to differentiate two different types of bacteria
iodine binds to crystal violet creating what
CV-I
what does blood agar select for?
selects for hemolytic activity
only differential media
types of blood agar
hemolysis types:
alpha
gamma
beta
alpha hemolysis
- INCOMPLETE LYSIS of red blood cells
- results in GREENISH HALO around the bacteria
beta hemolysis
- COMPLETE LYSIS of RBCs resulting in complete destruction of them
- will turn YELLOW around it
gamma hemolysis
- NO LYSIS of RBCs
- results in NO SIGNIFICANT CHANGE in the media
what is an endospore
a dormant bacteria (not metabollicly active)
blue color
will germinate under appropriate conditions (survival mechanism)
what is the layer that forms the plasma membrane in bacteria
peptidoglycan
does gram + have a thick or thin layer of peptidoglycan
thick
does gram -have a thick or thin layer of peptidoglycan?
thin
what is a capsule
a gelatinous layer that is secreted by the cell and that surrounds and adheres to the cell wall
components of gram staining
mixed culture
E.coli (G-)
S.epi (G+)
components of simple staining
MB (methylene blue)
CV (crystal violet)
carbol fusion
components of endospore staining
B. cereus
b. subtilis (bacillus)
components of acid fast stain
m. smeg
mycobacterium
s. megmatis
components of capsule stain
CV (crystal violet) - primary stain
copper sulfate- decolorizing agent
parts of the endospore staining procedure
primary stain- malachite green
decolorizing agent- water
counterstain- safranin
what would an autoclave be set to
121 degrees celcius ( 15 mins, 15 psi).
-(increasing temp, increases pressure to completely sterilize)
what is the optimum temp for growth of an organism
- room temp= 72 degrees Fahrenheit. 24 degrees Celsius
- human body temp= 98.6 degrees Fahrenheit. 37.5 degrees Celcius
identify the bacterial genus in which all species are acid fast
mycobacterium
why shouldn’t bacterial cells be placed in pure distilled water and what physiological changes will occur
too hypotonic. excess water rushes in, expanding the cell
describe the role of buffers in a bacteriological medium
resists radical changes/swings in the pH
identify the approximate pH at which most bacteriological media are generally adjusted
approximately 7.0
obligate aerobe
will only grow at the top of theoglycolate broth
needs oxygen to survive
obligarte anaerobe
will only grow at bottom of theoglycolate broth to get away from the oxygen
facultative anaerobe
will grow all throughout but cluster a little on the type.
can grow in oxygen or non oxygen environment but prefers oxygen
microaerophilic
prefers lower oxygen levels and higher CO2 levels and grows on top because still needs oxygen to survive
aerotolerant
grows all throughout, distributed evenly
microbicidal agents definition
kill microbes immediately
what are the different microbicidal and microbistatic agents
antiseptics
disinfectants
chemotherapeutic agents
microbistatic definition
stops the cell from reproducing
microbicidal definition
will kill the cell immediately
types of MacConkey agar
coliform bacteria
dysentery, typhoid, and paratyphoid bacilli
dysentery, typhoid, and paratyphoid bacilli
not fermenters
dont produce acid
tan or transparent
coliform bacteria
ferment lactose
red coloration
medium may be pink
why is heat used in acid fast staining
penetration is further enhanced: drives the carbol fuchsin through the lipoidal wall and into the cytoplasm
USED IN ZIEHL- NEELSON METHOD for acid-fast staining
Kinyoun method
circumvents the use of heat by addition of a wetting agent to the stain reducing surface tension between the cell wall of the mycobacterium and the stain.
steps in an acid-fast stain
primary stain- carbol fuschin
decolorizing agent- acid-alcohol (3% HCL + 95% Ethanol)
counterstain- methylene blue
