Deceptive Halo Formation by Tannase-Defective Bacteria on Tannin-Treated Plate Media

Abstract

Some bacterial strains that did not have tannase activity formed vague halos around their colonies on tannin-treated media. These halos were due to alkaline dissociation of the tannin-protein complex of the media during bacterial growth. All tannase-positive results obtained by the plate screening method should therefore be confirmed using a more analytical method.