BIOD 171: LAB EXAMS Q AND A
Using the observations made and recorded from PL09 Unknown Pathogen,
complete the results sections accordingly.
1. Given Culture A and Culture B were accidentally mixed, what
observations were made from the Gram stain (shown below)?
Gram-positive cocci (spherical) clusters and Gram-negative bacillus (rods) were
observed.
2. Given the results from a MacConkey agar plate shown below, what is
the shape of Culture A? Culture B?
MacConkey agar is selective for Gram-negative bacteria. Thus, Culture A
must be Gram- positive as no growth was observed. Coupled to the results
of the gram stain, Culture A (Gram-positive) must be the cocci.
, BIOD 171: LAB EXAMS Q AND A
Culture B must be Gram-negative (growth observed) and this correlates to
the bacillus or rod-shaped bacteria.
3. The hemolytic properties of both cultures were next examined by
streaking each culture on a blood agar plate (shown below). What is the
hemolytic status of Culture A? Culture B?
Culture A exhibits beta hemolysis as defined by the region of clearing around the
growing bacterial streak.
Culture B exhibits gamma-hemolysis (non-hemolytic) as indicated by the
white colonies growing on the still red agar.
,BIOD 171: LAB EXAMS Q AND A
, BIOD 171: LAB EXAMS Q AND A
Using the observations made and recorded from PL09 Unknown Pathogen,
complete the results sections accordingly.
1. Culture A and Culture B were streaked onto EMB plates. What does this tell
you about each of the cultures? Describe your observations.
EMB agar is both selective and differential media. EMB restricts Gram-positive
and as such this again confirms Culture A is Gram-positive. Culture B clearly
grew on the EMB plate, further confirming it is Gram-negative. A green metallic
sheen was also observed which immediately suggests Culture B is E. coli.
2. Culture A and Culture B were assessed via the catalase test as
shown below. State your observations for each culture.
Culture A and B were both catalase positive meaning both are able to breakdown
hydrogen peroxide (damages cellular integrity) into harmless hydrogen and
water molecules.
Using the observations made and recorded from PL09 Unknown Pathogen,
complete the results sections accordingly.
1. Given Culture A and Culture B were accidentally mixed, what
observations were made from the Gram stain (shown below)?
Gram-positive cocci (spherical) clusters and Gram-negative bacillus (rods) were
observed.
2. Given the results from a MacConkey agar plate shown below, what is
the shape of Culture A? Culture B?
MacConkey agar is selective for Gram-negative bacteria. Thus, Culture A
must be Gram- positive as no growth was observed. Coupled to the results
of the gram stain, Culture A (Gram-positive) must be the cocci.
, BIOD 171: LAB EXAMS Q AND A
Culture B must be Gram-negative (growth observed) and this correlates to
the bacillus or rod-shaped bacteria.
3. The hemolytic properties of both cultures were next examined by
streaking each culture on a blood agar plate (shown below). What is the
hemolytic status of Culture A? Culture B?
Culture A exhibits beta hemolysis as defined by the region of clearing around the
growing bacterial streak.
Culture B exhibits gamma-hemolysis (non-hemolytic) as indicated by the
white colonies growing on the still red agar.
,BIOD 171: LAB EXAMS Q AND A
, BIOD 171: LAB EXAMS Q AND A
Using the observations made and recorded from PL09 Unknown Pathogen,
complete the results sections accordingly.
1. Culture A and Culture B were streaked onto EMB plates. What does this tell
you about each of the cultures? Describe your observations.
EMB agar is both selective and differential media. EMB restricts Gram-positive
and as such this again confirms Culture A is Gram-positive. Culture B clearly
grew on the EMB plate, further confirming it is Gram-negative. A green metallic
sheen was also observed which immediately suggests Culture B is E. coli.
2. Culture A and Culture B were assessed via the catalase test as
shown below. State your observations for each culture.
Culture A and B were both catalase positive meaning both are able to breakdown
hydrogen peroxide (damages cellular integrity) into harmless hydrogen and
water molecules.
