CLASSIFICATION

Chromobacterium violaceum is the only species and the taxonomic problems are the separation from the other violacein producing genera; Janthinobacterium and Iodobacter. Janthinobacterium lividum and Iodobacter fluviatilis (Chomobacterium fluviatilis) each are the only species within their respective genera and were until recently considered members of the genus Chromobacterium. The differences between the genera include temperature range of growth, fermentation, and some of the tests listed below.

BIOCHEMISTRY

Chromobacterium violaceum is pigmented due to the production of violacein. Acid is produced from glucose, trehalose, N-acetylglucosamine and gluconate but not L-arabinose, D-galactose or D-maltose. It can produce cyanide. Lactate is utilised. Casein is hydrolysed and arginine decarboxylated.

There have not been many studies on the genetics of these organisms.

Apart from the differences in flagelar antigens as noted above, not many studies have been performed.

NORMAL FLORA

It is a small part of the normal flora of water and soils, where it may play a rôle in the rhizosphere. It is more commonly found in tropical or subtropical regions. It is not present as part of the normal flora of humans or animals.

Infections due to soil or water contamination with the organisms can be quite varied, ranging from mild diarrhoea to septicaemia leading to a rapid death. Liver and lung abscesses have been reported. Similar infections in animals have been reported.

C. violaceum grows easily on common culture media, which are suitable for the isolation of strains from patient specimens. However, these are not the best media to isolate these organisms from soil or water because C. violaceum is present in only small numbers. Sterile rice grains and reduced strength nutrient agar have been successfully used to isolate C. violaceum from soil or water.

Normally found in soil or water.

C. violaceum could be used for the production of violacein, which has antibiotic characteristics particularly against soil amoebae and trypanosomes. It can be used to assay for L-tryptophan.

It produces other antibiotics:

• Aerocyanidine is active against Gram-positive organisms.
• Aerocavin is active against Gram-positive and Gram-negative organisms.
• 3,6-dihydroxyindoxazene and Factor Y-T0678H (6-hydroxy-3-oxo-1,2-benzisoxazolin) are both active against Gram-negative bacteria.

 

A number of other important compounds are produced by C. violaceum including substances that enhance the immune response, compounds that act synergistically with beta-lactam antibiotics.

It has been suggested that C. violaceum strains can be used for the extraction of gold from soil. As a result of the production of cyanide, which reacts with the gold to form the complex anion [Au(CN)2]-, the gold is solubalised and easily extracted.

There are currently no vaccines.

Chromobacterium

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