Microbiology 250 Lab
Practical Exam Questions
and Complete Solutions
Graded A+
Denning [Date] [Course title]
,brom cresol purple - Answer: indicator in MIO media that tests for decarboxylation of ornithine
positive result is a lavender-purple color
A
hydrogen peroxide - Answer: H2O2
used to test for organism's possession of catalase
copious amounts of bubbles are evidence for release of O2 as peroxide is broken down
2H2O2 + O2
iodine - Answer: indicates the presence or absence of starch
agar - Answer: solidifying agent purified from marine algae
colonial morphology - Answer: size, color, shape, elevation, consistency, form, margin, surface, optical
characteristics
should only be observed on isolated colonies
YA10SC - Answer: yeast agar loaded with 10% sucrose (table sugar)
encourages the growth of streptococcus organisms such as Streptococcus salivarius and Streptococcus
mutans
dental caries - Answer: result of bacterial fermentation of sugar, commonly sucrose
,Streptococcus mutans and Lactobacillus acidophilus are main microbes responsible for production of
acid that causes these
demineralization - Answer: as sugars are fermented an acid is made that dissolves the hard calcium layer
of enamel of the tooth
dental plaque - Answer: dense mass of bacteria
dental caries are formed under this
difficult to remove
microbes involved in advanced tooth decay - Answer: Actinomyces
Nocardia
fermentation - Answer: the chemical action of yeast on sugars
ubiquitous - Answer: term referring to the fact that microorganisms are found virtually everywhere
SMA plate - Answer: standard methods agar
used to assess viable bacterial growth of a sample
microscopic morphology - Answer: also known as cellular morphology
aids in the observation of microbial traits such as a cell shape, size, arrangement, stain reactions,
endospores
, primary shapes of bacteria - Answer: rod - Bacillus
sphere - coccus
spiral - Spirillum
parfocal - Answer: property of microscope which allows objectives to be changed without having to
refocus
refraction - Answer: the bending of light as it passes from one material to another
immersion oil - Answer: addition of this minimizes the amount of light that is refracted or lost
size of coccus cell - Answer: about 1 micrometer on 100x
size of bacillus cell - Answer: about 4 micrometers on 100x
size of spiral cell - Answer: about 15 micrometers on 100x
size of average bacteria - Answer: 0.2 micrometers to 3.0 micrometers
can reach a length of 10 micrometers
arrangements of bacilli - Answer: singles, diplo, strepto, palisades
arrangements of cocci - Answer: singles, diplo, strepto, tetrads, sarcinae, staphylo
arrangements of spiral - Answer: vibrio, spirilla, spirochete (axial filament), stella, cubic, coccobacillus
Practical Exam Questions
and Complete Solutions
Graded A+
Denning [Date] [Course title]
,brom cresol purple - Answer: indicator in MIO media that tests for decarboxylation of ornithine
positive result is a lavender-purple color
A
hydrogen peroxide - Answer: H2O2
used to test for organism's possession of catalase
copious amounts of bubbles are evidence for release of O2 as peroxide is broken down
2H2O2 + O2
iodine - Answer: indicates the presence or absence of starch
agar - Answer: solidifying agent purified from marine algae
colonial morphology - Answer: size, color, shape, elevation, consistency, form, margin, surface, optical
characteristics
should only be observed on isolated colonies
YA10SC - Answer: yeast agar loaded with 10% sucrose (table sugar)
encourages the growth of streptococcus organisms such as Streptococcus salivarius and Streptococcus
mutans
dental caries - Answer: result of bacterial fermentation of sugar, commonly sucrose
,Streptococcus mutans and Lactobacillus acidophilus are main microbes responsible for production of
acid that causes these
demineralization - Answer: as sugars are fermented an acid is made that dissolves the hard calcium layer
of enamel of the tooth
dental plaque - Answer: dense mass of bacteria
dental caries are formed under this
difficult to remove
microbes involved in advanced tooth decay - Answer: Actinomyces
Nocardia
fermentation - Answer: the chemical action of yeast on sugars
ubiquitous - Answer: term referring to the fact that microorganisms are found virtually everywhere
SMA plate - Answer: standard methods agar
used to assess viable bacterial growth of a sample
microscopic morphology - Answer: also known as cellular morphology
aids in the observation of microbial traits such as a cell shape, size, arrangement, stain reactions,
endospores
, primary shapes of bacteria - Answer: rod - Bacillus
sphere - coccus
spiral - Spirillum
parfocal - Answer: property of microscope which allows objectives to be changed without having to
refocus
refraction - Answer: the bending of light as it passes from one material to another
immersion oil - Answer: addition of this minimizes the amount of light that is refracted or lost
size of coccus cell - Answer: about 1 micrometer on 100x
size of bacillus cell - Answer: about 4 micrometers on 100x
size of spiral cell - Answer: about 15 micrometers on 100x
size of average bacteria - Answer: 0.2 micrometers to 3.0 micrometers
can reach a length of 10 micrometers
arrangements of bacilli - Answer: singles, diplo, strepto, palisades
arrangements of cocci - Answer: singles, diplo, strepto, tetrads, sarcinae, staphylo
arrangements of spiral - Answer: vibrio, spirilla, spirochete (axial filament), stella, cubic, coccobacillus
