MICROBIOLOGY LAB TEST|| FINAL
LAB PRACTICUM MICROBIOLOGY
REVIEW LATEST QUIZ/ANSWER
WELL DEFINED 2024/2025
DISTINCTION ASSUARANCE
glucose test (CORRECT ANSWER)When oxygen is present, the
process is called oxidation, and when oxygen is absent it is called
fermentation. Reagents used: Phenol red glucose broth. Positive
reaction: If only the aerobic tube has turned yellow then the organism is
able to oxidase glucose aerobically ("O"). By-products: CO2 and
although organic acids may be present at low rates. Negative reaction: If
both tubes are yellow then the organisms is capable of fermentation
("F")
lactose test (CORRECT ANSWER)The purpose is to see if the microbe
can ferment the carbohydrate (sugar) lactose as a carbon source.
Reagent: Phenol red lactose broth. formation of acidic end products.
Negative reaction: Red (alkaline) Positive Reaction: yellow (acidic)
citrate test (CORRECT ANSWER)ability of an organism to use citrate
as its sole carbon source (instead of utilizing glucose) Positive reaction:
Blue dye will show positive blue color when pyruvate produced and
increase in pH. Negative reaction: the organism doesn't utilize citrate
and its still green
, MacConkey Agar test (CORRECT ANSWER)a selective and
differential medium designed to isolate and differentiate enterics based
on their ability to ferment lactose. Positive reaction: Neutral red is a pH
indicator that turns red at a pH below 6.8. Negative Reaction: is
colorless at any pH greater than 6.8.
Mannitol salt agar test (CORRECT ANSWER)If an organism can
ferment mannitol, an acidic byproduct is formed that will cause the
phenol red in the agar to turn yellow. Most pathogenic staphylococci,
such as Staphylococcus aureus, will ferment mannitol. Most non-
pathogenic staphylococci will not ferment mannitol.
Catalase test (CORRECT ANSWER)This test is used to identify
organisms that produce the enzyme, catalase. This enzyme detoxifies
hydrogen peroxide by breaking it down into water and oxygen gas
reagent: hydrogen peroxide. positive reaction: bubbles resulting from
production of oxygen gas. negative reaction: no bubbles meaning
catalase negative
Mesophiles (CORRECT ANSWER)bacteria that grow best at moderate
temps. Optimal growth between 20C-50C. Human pathogens are
classified as mesophiles. Ex: Staphylococcus aureus, Streptococcus
pyrogenes, Streptococcus pneumoniae, Escherichia coli.
Thermophiles (CORRECT ANSWER)Organisms that thrive in very
high temperatures.Optimal growth between 50C - 80C. Soil/compost
piles. EX: Geobacillus stearothermophilus
LAB PRACTICUM MICROBIOLOGY
REVIEW LATEST QUIZ/ANSWER
WELL DEFINED 2024/2025
DISTINCTION ASSUARANCE
glucose test (CORRECT ANSWER)When oxygen is present, the
process is called oxidation, and when oxygen is absent it is called
fermentation. Reagents used: Phenol red glucose broth. Positive
reaction: If only the aerobic tube has turned yellow then the organism is
able to oxidase glucose aerobically ("O"). By-products: CO2 and
although organic acids may be present at low rates. Negative reaction: If
both tubes are yellow then the organisms is capable of fermentation
("F")
lactose test (CORRECT ANSWER)The purpose is to see if the microbe
can ferment the carbohydrate (sugar) lactose as a carbon source.
Reagent: Phenol red lactose broth. formation of acidic end products.
Negative reaction: Red (alkaline) Positive Reaction: yellow (acidic)
citrate test (CORRECT ANSWER)ability of an organism to use citrate
as its sole carbon source (instead of utilizing glucose) Positive reaction:
Blue dye will show positive blue color when pyruvate produced and
increase in pH. Negative reaction: the organism doesn't utilize citrate
and its still green
, MacConkey Agar test (CORRECT ANSWER)a selective and
differential medium designed to isolate and differentiate enterics based
on their ability to ferment lactose. Positive reaction: Neutral red is a pH
indicator that turns red at a pH below 6.8. Negative Reaction: is
colorless at any pH greater than 6.8.
Mannitol salt agar test (CORRECT ANSWER)If an organism can
ferment mannitol, an acidic byproduct is formed that will cause the
phenol red in the agar to turn yellow. Most pathogenic staphylococci,
such as Staphylococcus aureus, will ferment mannitol. Most non-
pathogenic staphylococci will not ferment mannitol.
Catalase test (CORRECT ANSWER)This test is used to identify
organisms that produce the enzyme, catalase. This enzyme detoxifies
hydrogen peroxide by breaking it down into water and oxygen gas
reagent: hydrogen peroxide. positive reaction: bubbles resulting from
production of oxygen gas. negative reaction: no bubbles meaning
catalase negative
Mesophiles (CORRECT ANSWER)bacteria that grow best at moderate
temps. Optimal growth between 20C-50C. Human pathogens are
classified as mesophiles. Ex: Staphylococcus aureus, Streptococcus
pyrogenes, Streptococcus pneumoniae, Escherichia coli.
Thermophiles (CORRECT ANSWER)Organisms that thrive in very
high temperatures.Optimal growth between 50C - 80C. Soil/compost
piles. EX: Geobacillus stearothermophilus
