Table 1.

Morphological and biochemical characteristics of F. columnare (adapted from[1,3,10-12])

Characteristic	Description
Growth condition	Strictly aerobic
Gram-stain	Gram-negative
Morphology	Long, slender gliding rods of 4 to 10 μm and 0.3 to 0.5 μm wide. In aging cultures spheroplasts may occur
Capsule	Described to be absent [10] or present [11] depending on the adopted strain
Congo red absorption	Present due to an extracellular galactosamine glycan in the mucus and the production of flexirubin-type pigments
H2S-production	Present
Degradation of crystalline cellulose	Absent
Degradation of complex acidic polysaccharides of connective tissue	Present