Download Pigment Test (WINTER 2014 version) Introduction Pigments are

Pigment Test (WINTER 2014 version)
Introduction
Pigments are molecules that have color. Some bacteria produce pigments as part of their normal metabolism.
The specific color of the pigment is characteristic for each bacterium.
Pigmentation is determined by growing your organism on an UNCOLORED growth medium like TSA or
NAYE. Pigmented bacteria will form cultures that exhibit some color. Some pigments are water-soluble—they
leak out of cells and diffuse through the water-based culture medium. This causes the medium to change color.
Other pigments are water-insoluble—they remain within the cells, so only the colony (not the surrounding
medium) becomes colored.
Pigmentation can be a difficult characteristic to use. Many bacterial strains produce only small amounts of
pigment. Therefore, pigment should only be used as a characteristic if the presence of pigmentation is obvious.
A negative result for pigmentation is fairly meaningless.
Results
+ = Positive (color production on an uncolored medium)
- = Negative (no color production on an uncolored medium)
Caution 1: Pigmentation can only be ascertained on uncolored media such as NAYE and/or TSA.
Caution 2: Pigmentation can be a difficult characteristic to evaluate. If you have definite color formation (not
white, not off-white) then you can conclude your organism is pigment positive.
Methods
1. Inoculate an uncolored medium (TSA or NAYE slant or plate) and incubate at an appropriate temperature
(whatever temperature your organism grows well at).
OR
Use a previously inoculated TSA or NAYE slant or plate of your pure culture.
2. Observe the colonies and the medium for color formation.
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