The ability of strains of Bacillus, Staphylococcus, Pseudomonas, and E
scherichia coli to inactivate rifampicin was tested. Most Bacillus str
ains were found to inactivate rifampicin. Two modes of inactivation we
re identified; one was phosphorylation and the other involved decolori
zation. Presence or absence of either mechanism appeared unrelated to
the phylogenetic relatedness of strains. None of the other organisms c
ould inactivate this antibiotic.