How can we help?

You can also find more resources in our Help Center.

Microbiology practical 3

Dr. Raymond Mesa Community College
Aspergillus niger. Macroscope
What is this?
Aspergillus niger. Microscope
What is this?
Penicillium. Macroscope
What is this?
Penicillium. Microscope
What is this?
Rhizopus. Macroscope
What is this?
Rhizopus. Microscope
What is this?
Saccharomyces cerevisiae (yeast) macroscope
What is this?
Saccharomyces cerevisiae (yeast) Microscope
What is this?
It grows on yeast or mold depending on the enviornment.
Explain why Coccidiodes immitis is considered to be a dimorphic fungus?
Vegetative hyphae: It grows down or into agar
Areal hyphae: Grows above surface of agar
Explain the difference between vegetative hyphae and arial hyphae
Asexual spores produced at the end of arial hyphae in a sac like structure
Describe a sporangiospore
Formed on hyphae, can be one celled or multi-celled.
Describe a condiospore
Viruses that infect bacteria
Define bacteriophage
Virus' that burst open their bacterial host once the appropriate amount of viruses have been made then killing its host, the bacteria
Define lytic
On a streak plate where bacteria used to be there will be "empty" spots, this is where the virus landed, infected, and lysed the bacteria
Define plaque
To get a countable plaque number of around 30
Explain the the purpose of making dilutions of the T4 virus'
44 x 10^-8 x 10^-1 =
44 X 10= 4.4x10^10 PFU/ml
plaque dilution sample
count factor amount
Calculate the titer of phage in the original sample given the number of plaques and the dilution of the plate.
44 x 10-8 x 10-1 =
plaque __ dilution sample __ count factor amount=
Organisms that grow only inside another living host
Define obligate intra-cellular parasite
Bacteria: Regular agar broth media
Bacteriophage: Host cell, no media
How does the media used for bacterial growth differ from media used for bacteriophage growth?
Catalase reagent: hydrogen peroxide, it bubbles/no bubble
Coagulase: Rabbit plasma, it clumps or doesn't clump
Explain the principle state and reagent/media used in the catalase and coagulase test
Using the coagulas test, Staphylococcus aureus is positive. Staphylococcus epidermidis is negative. The "S" in Staphylococcus needs to me capitalized and the "e" in epidermidis and the "a" in aureus needs to be lower case. The whole thing should be underlined. You need to know the correct spelling for both.
Requires pen and paper Differentiate the 2 species of Staphylococcus by the coagulate test and who's positive and negative. When writing answer, what rules need to be followed?
Is Staphylococcus (+) or (-) using the catalase test?
Is Streptococcus (+) or (-) using the catalase test?
Staphylococcus aureus is yellow meaning it's (+) for mannitol fermentation
Staphylococcus epidermidis (-) is pink or red
Differentiate the 2 species of Staphylococcus by the reaction on the Mannitol salt agar?
It is selective because organisms that grow best in high salt concentrations grow here. It is differential for different species of Staphylococcus.
Explain how Mannitol salt agar is both a selective and differential media.
Micrococcus roseus is rose colored.
Micrococcus luteus is yellow colored.
Determine the species of Micrococcus by the pigmentation test.
Micrococcus roseus is (+)
Micrococcus luteus is (-)
Determine the species of Micrococcus by the nitrate test.
Gram (+) cocci in clusters
Are Staphylococcus and Micrococcus gram (+) or gram (-)? Are they in singles, pairs, chains, or clusters?
On the skin and mucus membrane
Where are Staphylococcus and Micrococcus normally found on the body?
Something that carries a pathogen but exhibits no symptoms
Define carrier
A pathogen resistant to penicillin derivatives such as methicillin and oxacillin
Define MRSA
A hospital acquired infection
Define nosocomial
When an opportunistic host presents its self
When do Staphylococcus epidermidis and Micrococcus cause disease?
Alpha. Greenish brown halos around isolated colonies
What type of hemolysis of an organism is growing on this blood agar?
Beta. You can see through the plate
What type of hemolysis of an organism is growing on this blood agar?
Gamma. White bacteria growing on red plate
What type of hemolysis of an organism is growing on this blood agar?
You "stab" to see hemolysis better
Explain why you use the streak stab method for blood agar inoculations
In a candle jar because its a Microaerophile
State the atmosphere used to grow streptococcus
Larger, raised, opaque, frequently pigmented
Describe the colony appearance of Staphylococcus
Translucent to semi opaque
Describe the colony appearance of Streptococcus
Which enzyme helps differentiate staphylococci from streptococci
It's based on the C polysaccharide extracted from the cell walls
How did Lancefield devide the beta-hemolyic streptococci into groups?
Streptococci pyogenes
What is the species name of Lancefield Group A streptococci?
Streptococci agalactiae
What is the species name of Lancefield Group B streptococci?
GI tract
Where are Enterococcus normally found in the human body?
Vancomycin resistant enterocccus
Define VRE
Alpha hemolytic streptococci other than Streptococci pneumonia
Define viridans streptococci
Strep throat
Group A Strep causes what disease?
Neonatal septicemia (An infant blood infection)
Group B Strep causes what disease?
Urinary tract infection
Enterococcus causes what disease?
Community-acquired pneumonia
Streptococcus pneumoniae causes what disease?
Dental cavities
viridans streptococci causes what disease?
CNA grows grows only gram (+) organisms and MacConkey only grows gram (-) organisms
Explain how CNA and MacConkey agar aid in the identification of bacteria in a mixed unknown
What ingredient in the MacConkey agar will differentiate the organisms growing in the agar?
Crystal violet and bile salts
How does the CNA medium prevent the growth of gram (-) rods?
What ingredient in the CNA media allows differentiation of the organisms growing in the agar?
Streptococcus are microaerophilic
Why is CNA media incubated in a candle jar?
It's a neutral media that all bacteria will grow on
Why is T. soy agar used to grow "stock cultures"?
Staphylococcus aureus
Unknown: Coagulase test, clumps
Staphylococcus epidermidis
Unknown: Coagulase test, no clumps
Staphylococcus aureus positive
Unknown: Mannitol salt agar, negative or positive test result?
Staphylococcus epidermidis negative
Unknown: Mannitol salt agar (quadrant 1 and 2) Positive or negative test result?
Micrococcus roseus
Unknown: Pigment Production (colony color)
Micrococcus luteus
Unknown: Pigment Production (colony color)
Micrococcus roseus positive
Nitrate reduction- turns red with alpha-napththylamine and sulfuric acid. Is this a positive or negative tests result?
Micrococcus luteus negative
Nitrate reduction- Turns red after zinc
Is this a positive or negative tests result?
Alpha Streptococcus mitis and Streptococcus pneumoniae
Unknown hemolysis to detemine bacteria
Streptococcus mitis
Unknown optochin sensitivity test.
Streptococcus pneumoniae
Unknown optochin sensitivity test.
Beta Streptococcus pyogenes and Group C Streptococcus.
Unknown hemolysis test to determine bacteria
Group C Streptococcus
Unknown bacitracin sensitivity test
Streptococcus pyogenes
Unknown bacitracin sensitivity test.
Enterococcus faecalis
Unknown bile esculin test (tube on the right)
Micrococcus luteus positive
Nitrate reduction- No red color after zinc
Is this a positive or negative tests result?
Gram (+)
Does CNA grows gram (+) or Gram (-) ?
Gram (-)
Does MacConkey grow gram (+) or Gram (-) ?