Some bacteria are able to reduce some organic colorants (methylene blue, malachite green, Janus green) to
colorless substances that regain initial color in oxygen presence.
MEDIUM PREPARATION: to every 5 ml nutritive broth medium, add 1 drop
of methylene blue 1% solution.
Inoculate a medium tube with bacterial culture then add paraffin oil to
create low oxygen growth conditions. Incubate at 37 ˚C, 24 hours.
Full discoloration indicates a positive reaction.
Green color indicates a weak positive reaction.
Reaction is negative if blue color persists.
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
(c) Costin Stoica
|Methylene blue decomposition test
positive (left) & negative (right)