Flexirubin is the main pigment in the bacteria genera ''

Flexibacter ''Flexibacter'' is a genus of bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a f ...

'', ''

Flavobacterium ''Flavobacterium'' is a genus of Gram-negative, nonmotile and motile, rod-shaped bacteria that consists of 130 recognized species. Flavobacteria are found in soil and fresh water in a variety of environments. Several species are known to cause ...

'', ''

Chryseobacterium ''Chryseobacterium'' is a genus of Gram-negative bacteria. ''Chryseobacterium'' species are chemoorganotrophic, rod shape gram-negative bacteria. ''Chryseobacterium'' form typical yellow-orange color colonies due to flexirubin-type pigment. The g ...

'', and ''

Cytophaga ''Cytophaga'' is a genus of Gram-negative, gliding, rod-shaped bacteria. This bacterium is commonly found in soil, rapidly digests crystalline cellulose ''C. hutchinsonii'' is able to use its gliding motility to move quickly over surfaces. Al ...

''.Reichenbach, H., W. Kohl, et al. (1980). ''FLEXIRUBIN-TYPE PIGMENTS IN FLAVOBACTERIUM''. Archives of Microbiology 126(3): 291–293. It was isolated for the first time from '' Flexibacter elegans''. Flexirubin is found in these genera, as well as those that produce

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

s. The pigment mixture of flexirubin and carotenoids imparts

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

with an intense yellow-orange color.Hans Achenbach, W. Kohl, et al. (1976). ''INVESTIGATIONS ON METABOLITES OF MICROORGANISMS .11. FLEXIRUBIN, A NOVEL PIGMENT FROM FLEXIBACTER-ELEGANS''. Chemische Berichte-Recueil 109(7): 2490–2502. Structurally, this bacteria pigment is based on a polycarboxylic-

chromophore A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molec ...

that is linked with a

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...

by an

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

, resulting in an

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloalk ...

side-chain. The first

total synthesis Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes ...

of flexirubin was reported in 1977.Achenbach, H. and J. Witzke (1977). ''TOTAL SYNTHESIS OF FLEXIRUBIN DIMETHYL ETHER''. Angewandte Chemie-International Edition in English 16(3): 191–192. To test for the presence of flexirubin, a cultural strain with a 20%

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

solution is created. A color change from gold to red-brown indicates the presence of flexirubin. Alternatively, the pigment can also be extracted with

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

and chromatographic methods can be used to ascertain its presence.

References

Phenols Phenol esters Alkyl-substituted benzenes Pigments