Appearance Violet-red needles | ||
Flexirubin is the main pigment which occurs in the Bacteria genera of Flexibacter, Flavobacterium, Chryseobacterium and Cytophaga. It was isolated for the first time from Flexibacter elegans. Flexirubin is found in these genera, as well as those which produce carotenoids. The pigment mixture of flexirubin and carotenoids imparts colonies with an intense yellow-orange color. Structurally, this bacteria pigment is based on a polycarboxylic-chromophore which is linked with a phenol by an ester, resulting in an alkyl side-chain. The Total synthesis of Flexirubin was documented in 1977.
To test for the presence of flexirubin, a cultural strain with a 20% potassium hydroxide solution is created. A color change from gold to red-brown displays the presence of Flexirubin. Optionally, the pigment can also be extracted with acetone and chromatographic methods can ascertain its presence.