Lab Practical: BIOS 242 / BIOS242 Review (Latest 2024/ 2025 Update) Microbiology| Questions and Verified Answers| 100% Correct| Grade A- Chamberlain
Lab Practical: BIOS 242 / BIOS242 Review_ Answer: stiff Q: pleomorphic is __
Answer:is long chains of cocci is long chains of bacillus_ is clusters of cocci Answer: staphylcocci Q: is clusters of rods_ )- carbolfuschin is primary dye- heat to drive stain inside
Q: _ )- for bacteria with mycolic acid(_ )-background is dark, primary stain is eosin_ ( )- thin hair like, hard to stain ( and )- malachite green , heat to drive stain inside / _ – the organism is spread out on the plate to give lawn of growth after incubation. Filter paper soaked in antibiotic solution is placed onto the plate prior to incubation. During incubation the drug will diffuse out and , if it is effective, will give a clear zone of where growth is prevented Answer: Kirby Bauer / disk diffusion test Q: ________ https://learnexams.com/search/study?query=lab
________ and _____ ______ ______ are used to focus the microscope
course and fine focus knobs
_______ is where the specimen to be viewed is placed
stage
______ ______ the primary optical lenses on a microscope.
optical lens
optical lens range from _X-_____X
4X-100X
_______ is the light source for a microscope, typically located in the base of the microscope
illuminator
______ connects to the base and supports the microscope head. It is also used to carry the microscope
neck/arm
________ of the microscope supports the microscope and houses the illuminator
base
_______ _____-regular agar plate with added nutrients to promote growth
nutrient agar plate
______- liquid medium lacks a solidifying agent
broth
_____- agar in petri dish and cooled this provides large surface areas for the isolation and study of microorganisms
plate
_____ _______- stain purple, have thick layer of peptidoglycan
gram positive
______ _____- stain pink, contains much thinner layer of peptidoglycan
gram negative
shape: cocci
round
shape: bacillus
long and skinny
spirochete is _______
flexible
spirillum is _____
stiff
pleomorphic is ______ _____
multiple shapes
_______ is long chains of cocci
Streptococci
_______ is long chains of bacillus
streptobacilli
______ is clusters of cocci
staphylcocci
______ is clusters of rods
staphylobacilli
______ ______ (________)- carbolfuschin is primary dye- heat to drive stain inside
acid fast (mycobacterium)
______ _____ (_______)- for bacteria with mycolic acid
acid fast (mycobacterium)
______ (________)-background is dark, primary stain is eosin
capsule (klebsiella)
______ (______)- thin hair like, hard to stain
flagella (e.coli)
_________ (________ and _________)- malachite green , heat to drive stain inside
endospore (clostridium and bacillus)
______ _____/ ____ ______ _____- the organism is spread out on the plate to give lawn of growth after incubation. Filter paper soaked in antibiotic solution is placed onto the plate prior to incubation. During incubation the drug will diffuse out and , if it is effective, will give a clear zone of where growth is prevented
Kirby Bauer / disk diffusion test
______________- indicated the level of sensitivity or an organism to a drug
zone of inhibition
gram staining: steps 1-9
1) stain with crystal violet for 1 minute
gram staining step 1: stain crystal violet for 1 minute:
this stains all cells, both G+ and G-, PURPLE
gram staining step 5: add 95% alcohol drop by drop until alcohol runs almost clear:
this process decolorized G- cells. The G+ cells remain purple because the dye cannot leave through the thick layer of peptidoglycan
gram staining step 7: counterstain with safranin for 45 seconds:
this stains the now colorless G- cells PINK
_____ ____ uses H2O2 to determine if the bacteria can use oxygen or not. If the test is positive (produces bubbles) the organism is Staphylococci, if the test is negative (no bubbles) the organisms is streptococci
catalase test
catalase test- positive:
produces bubbles and organism is staphylococci
catalase test- negative:
non bubbles and the organism is steptococci
______ ______ _____(____)- key ingredient is sheep blood; tested on bacteria inoculated from a patient’s throat swab to test for the presence of streptococci
Blood Agar Plate (BAP)
______ _____- the bacteria’s hemolytic enzymes completely break the blood cells- the pattern results in the media displaying a clear halos around bacterial colonies (ex. streptococcus pyogenes)
beta hemolysis
______ _____- the bacterial enzymes only partially break down the blood cells -the results in the media showing a yellowish/greenish/brownish discoloration (like a bruise) around the colony, indicating incomplete hemolysis (ex. normal flora)
alpha hemolysis
_____ ____- essentially no hemolysis at all- bacteria have no effect on the red blood cells, and there is no change to the color of the medium (ex. normal flora)
gamma hemolysis
________- exhibit color change when a certain kind of microorganisms grows
differential
_________- allows growth of only certain types of microbes and inhibits growth of other types of microbes
selective
________:
differential
_______:
selective
________ _______- key ingredients are NaCl and mannitol salt; tested on bacteria inoculated from human skin
MSA plate
______ _______ (pathogenic) is mannitol fermenter and turns MSA a bright yellow color
staphylococcus aureus
_______ ______(normal flora) does not ferment mannitol and the naturally orange-pink color of the agar does not change
staphylococcus epidermidis
_______ _____- key ingredients are neutral red (pH indicator), lactose (disaccharide), crystal violet, and bile salts
MacConkey Agar
_________ _____:
MacConkey Agar
__________ _____:
MacConkey Agar
_______ ____: selective and differential medium used to isolate fecal coliforms. Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH
EMB plate
______ _____: selective medium used to cultivate gram + organisms. Active ingredient: phenylethyl alcohol, which inhibits growth of gram- organisms by interfering with DNA synthesis
PEA plate
______ _____ exhibits color change when a certain kind of microorganisms grows on them giving us information about the type of microbe growing there
differential media
_______ ____ allows growth of only certain types of microbes and inhibits the growth of other types of microbes
selective media
what is the purpose of high salt in mannitol salt agar?
inhibits growth of negative organisms, selective for halophiles, can differentiate pathogenic and non pathogenic staphylococcus
what is the purpose of lactose in MacConkey Agar?
for fermentation and termination and if it ferments it turns the dye red (pink)
what is the purpose of blood in blood agar?
blood acts as an enrichment ingredient for cultivation of fastidious organisms, blood also permits demonstrations of hemolytic properties
what is the purpose of phenylethyl alcohol agar?
inhibits effects of gram- organisms
what is the purpose of eosin and methylene blue dyes in eosin-methylene blue agar?
allows growth of G- bacteria. It isolated fecal coliforms
why is phenol red added to the fermentation tubes? how does it work?
phenol red is added as a pH indicator. Phenol red will turn yellow below pH of 6.8 and a dark pink red above a pH of 7.4. Yellow will mean it is acidic, The pink is basic
why is it important not to incubate the fermentation tubes beyond 24 hours?
if the fermentation tubes are incubated beyond 24 hrs, the acids may be further metabolized and converted back to neutrality or even alkalinity
e. coli ferments ______ and ______
lactose and dextrose
s epidermidis ferments _______ but not _____
lactose but not dextrose
s marcesens ferments _______ but not ______
lactose but not dextrose
b subtilis ferments _______ and ________
lactose and dextrose
explain why the light microscope is also called the compound microscope:
there are several lenses
explain why the specimen must be centered in the field of view on low power before going to high power:
on high power its harder to find specimen, it is also nearly impossible to find if not centered b/c that means it wouldn’t be in the field of view
a microscope has a 20X ocular eyepiece and two objectives of 10X and 40X what is the low and high-power magnification:
200X and 860X
simple staining: did you air dry your smear before heat fixing it? Why do you think this is important?
yes, this is important bc air drying will ensure that all water is dried. It is important to make sure that water is dried bc if you heated the slide while it was wet, the water would change the features of the bacterial cells on the slide which will cause the cells to burst
simple staining: how different will your results be if you forget to heat fix your sample before staining it?
the bacteria may wash off when you stain and not heat fixing will cause bacteria to stay on the slide
simple staining: which dye did you use to stain your sample? is it acidic or basic in nature? Give your reasons for using this dye:
used crystal violet to stain my sample which is basic in nature, staining cells makes it easier to observe bacteria bc w/o using the dye it would become difficult to see cells bc they are transparent and the cells are negatively charged
differential staining: describe the difference between gram+ and gram- cell walls
gram- cell walls contain a thin peptidoglycan layer, it is also surrounded by plasma membrane. Gram+ cells have thick peptidoglycan layer and will stain purple
differential staining: what causes gram- bacteria to stain pink?
gram- cannot retain the crystal violet because of a thin peptidoglycan layer
differential staining: what causes gram+ bacteria to stain purple?
gram+ appears purple bc it retains the dye because of the thick peptidoglycan layer
differential staining: what is the purpose of iodine in the gram stain’s procedure?
iodine is used in gram staining because of mordents, which is bc it increases the affinity of the cells for a stain which makes gram- and gram+ purple
fomite transmission is _____
indirect
______ ______ spread of infection from one host to another by direct contact, indirect contact or respiratory droplets
contact transmission
_____ ______ spread of pathogen via air, drinking water, and food, as well as bodily fluids being handles outside the body
vehicle transmission
_______ animals that transmit diseases from one host to another
vectors
______- agar is cooled in a _____ position, these are useful for maintaining pure cultures
slants, cooled in a slanted position
_______ plate grows gram pos bacteria, and mimics the resp. system
PEA
PEA plate is diff/selective; dye used is _____ and _____
Selective; eosin y and methylene blue
what is the active ingredients in MSA plates?
mannitol and salt
MSA plate grows gram ________ bacteria
positive
MSA plate mimics what body system?
skin (integumentary)
blood agar plate active ingredient
5% sheep blood
what body system does BAP (blood agar plate) mimic?
respiratory
what reaction occurred with pyogenes on BAP
beta hemolysis
what reaction occurred with s.epi on BAP
gamma hemolysis
what reaction occured with s. aureus on BAP
alpha hemplysis
MacConkey Agar active ingredients
bile salts, crystal voilet
MacConkey Agar mimics what body system?
GI system
__________________ plates grow gram negative bacteria only
MacConkey
acid fast staining
EMB plate is _______________________
selective and differential
deep agar
flagellar stain
agar broth
agar slant
fermintation: PRB tubes (phenyl red indicator)
EMB Plate
On a MSA plate, what does yellow and red reaction mean?
yellow= acid/ fermentation
