Microbiology
Lab Worksheet
Name:___________________________
LAB 12: SELECTIVE VS. DIFFERENTIAL MEDIA
Growth Media, such as Tryptic Soy Agar (TSA), are considered all-purpose (____________)
in that a very _______________ _______________ of bacterial genera can be grown on it.
Other media are selective and _________________________ some genera and not others.
Other media are considered _________________________.
Differential media enable the researcher to easily ___________________ _____________
different genera using growth characteristics (especially color differences).
There is no media that is considered _______________________ in that it can be used for all
microbial growth.
Conditions of incubation come into play as well as the ________________________ needed.
The following media are considered ______________________________. Tryptic Soy Agar
and Broth, Nutrient Agar and Broth, Blood Agar, and several others.
These media types can be used to grow a __________________ ____________________ of
soil microbes, pathogens, and human body flora.
Media that contains dyes and other chemicals that can inhibit the growth of certain microbes is
termed __________________________.
Levine EMB Agar inhibits the growth of _________________________ bacteria and selects
for the growth of ____________________________________.
Levine EMB can also be considered ________________________, because______________
___________________________________________________________________________
___________________________________________________________________________
Media that simplifies the task of distinguishing between various types of bacteria is considered
__________________________________.
This can be done by changing colonies various ___________________ or by the action of the
colonies on the media.
Levine EMB Agar is differential in that it distinguishes between Enterobacter aerogenes
(colonies _________________ to buff with _________________ centers), Escherichia coli
Microbiology
Lab Worksheet
Name:___________________________
(colonies have a ____________________ __________________ _______________), and
those that remain _________________________ (Pseudomonas, Salmonella, Shigella).
MacConkey Agar is employed in this lab and distinguishes between pathogenic
______________________ and ____________________ bacteria versus non-pathogenic
coliform and enteric bacteria.
Those that are pathogenic can generally ____________________ __________________ and
will have _____________ to _________ colonies while those that cannot ferment lactose will
be ________________________.
MacConkey Agar is often also considered a selective media because __________________
_________________________________________________________________________
_________________________________________________________________________.
Hektoen Enteric (HE) agar is also used to isolate & distinguish between _______________
coliform and enteric bacteria versus ___________________________________ coliform and
enteric bacteria.
It is particularly helpful in isolating Salmonella and Shigella in __________________ samples.
HE agar is both _____________________ and ______________________.
Lactose-fermenting bacteria will have an _______________________ pigment and organisms
that produce hydrogen sulfide (H2S) will turn the media _______________.
Citrate agar is used to detect if bacteria utilize _____________________________ as their
sole source of ______________________. The agar starts out green but will turn __________
if citrate is utilized.
This biochemical reaction helps to identify the organism – along with other biochemical
reactions such as _________________, ___________________, ___________________, etc.
Blood Agar is an all-purpose media that can also be used for differentiating between groups
and species of ___________________________________.
Streptococcus is well known for its _____________________________ properties. Checking
inoculated blood agar for alpha, beta, or gamma _______________________ helps discern
what Strep species might be involved.