R. D. Demoss

The violet pigment which was extracted from a bacterial culture in 1882 by BoiseAUDRAN was probably violacein. The absorption spectrum recorded by Boisbaudran was similar to those from later studies of crystalline violacein and it seems likely that the bacterium was a strain now known as Chromohacterium violaceum. It is probably significant (see below) that the culture was grown on starch paste and that the pigment was obtained —d un petit organisme que se developpe assez frequemment a la surface de la colle de farine conservee pendant quelque temps k Fair humide.  

The blue and purple components referred to by DeMoss and Evans (1959) undoubtedly correspond to violacein (the 5 hydrox3dndolyl derivative) and deoxyviolacein (5 - (3 -indolyl) -3 - (3 -oxindolylidene) -2-oxop5 roline) (Ballantine et al., 1958), respectively. 

A possible function of the pigment as a storage depot for indole residues, i.e., as a source of tryptophan precursors, is probably untenable. Active degradation of the pigment by the organism has not been observed. 

The pigment could conceivably be an accidental end product of tryptophan degradation. In another organism. Bacillus alvei, the degradation of tryptophan is postulated to be obligatory to maintain the intracellular level of tryptophan at a relatively low, non-toxic, concentration (Hoch and DeMoss, 1966). If a similar requirement for low internal tryptophan concentration exists in Chromohacterium violaceum, conversion of tryptophan to pigment would serve a useful metabolic function. 

Whatever the metabolic function of the pigment, it is apparently dispensable under laboratory conditions of growth on complex media. Pigmentless mutants arise, usually with troublesome frequency, during repeated transfer (of strain ATCC 553) oil nutrient agar medium. 

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Violacein the major purple pigment of Chromobacterium violaceum, accompanied by smaller amounts of deoxyviolacein. Every C-atom of V. is derived biosynthetically from tryptophan. oL-trypto-phan labeled with in the ring or side chain is incorporated with very little dilution into V. by nonproliferating cells of C. violaceum. [R.D.DeMoss N.R. Evans / Bact. 79 (1960) 729]... 

Hoch, j. a., and R. D. DeMoss Physiological role of tryptophanase in control of tryptophan biosynthesis by Bacillus alvei. J. Bacteriol. 91, 667 (1966). 

R. D. DeMoss, Department of Microbiology, University of lUinois, Urbana, lUinois/USA... 

DeMoss, R. D., and N. R. Evans Physiological aspects of violacein bios3mthesis in nonproliferating cells. J. Bacteriol. 78, 583 (1959). 

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