MCB 2010C FINAL LAB EXAM QUESTION AND
ANSWER (2025-2026) A+ RATED EXPERT VERIFIED
Question |1
What |kind |of |media |is |EMB?
complex, |selective, |and |differential
Question |2
What |is |the |EMB |media |composed |of?
gelatin, |lactose, |and |the |dyes |eosin |Y |and |methylene |blue
Question |3
What |kind |of |microbe |does |EMB |agar |inhibit?
gram |positive
Question |4
If |the |bacterium |changes |to |a |purple |color |on |EMB |agar, |what |does |that |mean?
The |bacterium |is |gram |negative, |and |ferments |lactose.
Question |5
What |bacterial |stocks |turn |purple |on |EMB |agar, |meaning |that |they |ferment |lactose?
Enterobacter |aerogenes, |Proteus |vulgaris, |and |Esherichia |coli
,Question |6
What |sheen |does |E. |coli |give |off |on |EMB |agar?
A |metallic |green |sheen
Question |7
What |kind |of |media |is |MAC?
Selective |and |differential
Question |8
What |is |the |MAC |media |composed |of?
Lactose, |bile |salts, |neutral |red, |and |crystal |violet.
Question |9
What |is |the |action |of |bile |salts |and |crystal |violet |in |MAC |media?
Inhibits |gram |positive |bacteria |growth
Question |10
What |is |the |pH |indicator |in |MAC |media?
Neutral |red
Question |11
If |a |bacterium |does |alter |the |color |of |MAC |media, |what |does |this |mean?
The |bacterium |is |gram |negative, |lactose |fermenting, |lowers |the |pH |of |the |media |(acidic) |and
|changes |the |media |from |pink |to |red.
Question |12
What |bacterial |stocks |turn |red |on |MAC |agar, |meaning |that |they |ferment |lactose |and |lower |pH?
Escherichia |coli |and |Enterobacter |aerogenes
, Question |13
What |is |the |pH |indicator |in |PR-G |tubes?
Phenyl |red
Question |14
If |the |bacterium |changes |to |a |yellow |color, |what |does |this |mean? |pink?
If |the |media |turns |yellow, |this |indicates |glucose |fermentation, |and |an |acidic |pH. |If |the |media |turns
|pink, |this |indicates |peptone |from |NH3 |production, |raising |the |pH |alkaline.
Question |15
What |does |the |durham |tube |in |the |PR-G |tube |indicate?
Gas |production |indicates |fermentation.
Question |16
What |bacterium |changes |yellow |in |PR-G |media?
Enterobacter |aerogenes, |Escherichia |coli, |and |proteus |vulgaris |(both |produced |gas)
Question |17
What |kind |of |media |is |PR-G |and |PR-L |tubes?
Differential
Question |18
What |bacterium |changes |to |yellow |on |PR-L |media, |meaning |it |ferments |lactose?
Enterobacter |aerogenes |and |Escherichia |coli |(both |produced |gas)
Question |19
What |kind |of |media |is |urea |broth?
Differential
ANSWER (2025-2026) A+ RATED EXPERT VERIFIED
Question |1
What |kind |of |media |is |EMB?
complex, |selective, |and |differential
Question |2
What |is |the |EMB |media |composed |of?
gelatin, |lactose, |and |the |dyes |eosin |Y |and |methylene |blue
Question |3
What |kind |of |microbe |does |EMB |agar |inhibit?
gram |positive
Question |4
If |the |bacterium |changes |to |a |purple |color |on |EMB |agar, |what |does |that |mean?
The |bacterium |is |gram |negative, |and |ferments |lactose.
Question |5
What |bacterial |stocks |turn |purple |on |EMB |agar, |meaning |that |they |ferment |lactose?
Enterobacter |aerogenes, |Proteus |vulgaris, |and |Esherichia |coli
,Question |6
What |sheen |does |E. |coli |give |off |on |EMB |agar?
A |metallic |green |sheen
Question |7
What |kind |of |media |is |MAC?
Selective |and |differential
Question |8
What |is |the |MAC |media |composed |of?
Lactose, |bile |salts, |neutral |red, |and |crystal |violet.
Question |9
What |is |the |action |of |bile |salts |and |crystal |violet |in |MAC |media?
Inhibits |gram |positive |bacteria |growth
Question |10
What |is |the |pH |indicator |in |MAC |media?
Neutral |red
Question |11
If |a |bacterium |does |alter |the |color |of |MAC |media, |what |does |this |mean?
The |bacterium |is |gram |negative, |lactose |fermenting, |lowers |the |pH |of |the |media |(acidic) |and
|changes |the |media |from |pink |to |red.
Question |12
What |bacterial |stocks |turn |red |on |MAC |agar, |meaning |that |they |ferment |lactose |and |lower |pH?
Escherichia |coli |and |Enterobacter |aerogenes
, Question |13
What |is |the |pH |indicator |in |PR-G |tubes?
Phenyl |red
Question |14
If |the |bacterium |changes |to |a |yellow |color, |what |does |this |mean? |pink?
If |the |media |turns |yellow, |this |indicates |glucose |fermentation, |and |an |acidic |pH. |If |the |media |turns
|pink, |this |indicates |peptone |from |NH3 |production, |raising |the |pH |alkaline.
Question |15
What |does |the |durham |tube |in |the |PR-G |tube |indicate?
Gas |production |indicates |fermentation.
Question |16
What |bacterium |changes |yellow |in |PR-G |media?
Enterobacter |aerogenes, |Escherichia |coli, |and |proteus |vulgaris |(both |produced |gas)
Question |17
What |kind |of |media |is |PR-G |and |PR-L |tubes?
Differential
Question |18
What |bacterium |changes |to |yellow |on |PR-L |media, |meaning |it |ferments |lactose?
Enterobacter |aerogenes |and |Escherichia |coli |(both |produced |gas)
Question |19
What |kind |of |media |is |urea |broth?
Differential
