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Genetic analysis of violacein biosynthesis by Chromobacterium violaceum
Regina Vasconcellos Antônio1 and Tânia B. Creczynski-Pasa2
1Departamento de Bioquímica, Centro de Ciências Biológicas, and
2Departamento de Ciências Farmacêuticas, Centro de Ciências da Saúde,
Universidade Federal de Santa Catarina, Caixa Postal 476, 88040-900 Florianópolis, SC, Brasil
Corresponding author: R.V. Antônio
Genet. Mol. Res. 3 (1): 85-91 (2004)
Received October 13, 2003
Accepted January 12, 2004
Published March 31, 2004

ABSTRACT. Chromobacterium violaceum presents a distinctive phenotypic characteristic, the production of a deep violet pigment named violacein. Although the physiological function of this pigment is not well understood, the sequencing of the genome of this bacterium has given some insight into the mechanisms and control of violacein production. It was found that erythrose-4-phosphate (E4P), a precursor to aromatic amino acid biosynthesis, is produced by the non-oxidative portion of the hexose monophosphate pathway, since it lacks 6-phosphogluconate dehydrogenase. All genes leading from E4P plus phosphoenolpyruvate to tryptophan are present in the genome. Nevertheless, these genes are not organized in an operon, as in E. coli, indicating that other mechanisms are involved in expression. The sequencing data also indicated the presence and organization of an operon for violacein biosynthesis. Three of the four gene products of this operon presented similarity with nucleotide-dependent monooxygenases and one with a limiting enzyme polyketide synthase. As previously suggested, genes encoding proteins involved in quorum sensing control by N-hexanoyl-homoserine-lactone, an autoinducer signal molecule, are present in the bacterial genome. These data should help guide strategies to increase violacein biosynthesis, a potentially useful molecule.

Key words: Chromobacterium violaceum, Tryptophan metabolism,Polyketide synthase, Tryptophan 2-monooxygenase, Violacein, N-acyl-homoserine synthase


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