| Types of Medium |
Enriched medium has had supplements added. Growth requirements
have been added to help microbes grow. An example of an enriched medium
is Blood Agar. Blood agar has a trypticase soy agar base that has had sheep
blood added. This is a picture of Staphylococcus aureus growing
on blood agar. |
|
| Selective media have had supplements added also but in
the case of selective media the supplement is added to aid in the growth
of some organisms while inhibiting the growth of other microbes. This is
a picture of Escherichia coli growing on a MacConkey agar plate.
MacConkey agar selects for organisms like Escherichia coli (Gram
negative bacilli) while inhibiting the growth of organisms like Staphylococcus
aureus (Gram positive cocci). |
|
| Differential media have supplements added that give a
distinctive appearance to different species. Differential media will aid
in a presemptive identification of the microbe. These are mannitol salt
agar plates. The plate on the right has Staphylococcus aureus growing
and changes the color of the agar to yellow. The plate on the left has Staphylococcus
epidermidis growing. The colonies are white and do not change the
color of the agar. |
|
