Chromobacterium violaceum

Overview

Chromobacterium violaceum is a Gram-negative, facultative anaerobic, non-sporing coccobacillus. It is motile with the help of a single flagellum which is located at the pole of the coccobacillus. Usually, there are one or two more lateral flagella as well. Chromobacterium violaceum produces a natural antibiotic called violacein, which may be useful for the treatment of colon and other cancers. It grows readily on nutrient agar, producing distinctive smooth low convex colonies with a dark violet metallic sheen (due to violacein production).

A close-up photograph of Chromobacterium violaceum colonies on an agar plate, showing their distinctive violet color.

Taxonomy

Chromobacterium violaceum is a member of the Neisseriaceae family, which includes a number of other Gram-negative bacteria. The genus Chromobacterium was first described in 1881, and C. violaceum is its type species. The species name 'violaceum' refers to the deep violet color of the colonies.

Habitat

C. violaceum is found in soil and water in tropical and subtropical regions. It has been isolated from the Amazon River and soils in Brazil, Malaysia, and the southern United States. It is not usually part of the human microbiota but can live on the skin without causing harm.

Pathogenicity

C. violaceum can cause infections in humans and animals, especially in immunocompromised individuals. Infections are rare but can be serious and life-threatening. They can result from skin contact with soil or water containing the bacteria, or from ingestion or inhalation. Symptoms can include skin lesions, sepsis, and liver abscesses. The bacteria can also cause a type of pneumonia when inhaled.

Antibiotic production

C. violaceum produces a number of natural antibiotics, including violacein and several others. Violacein has been shown to have anti-cancer properties and is being investigated for use in treating various types of cancer. It also has potential as an antimicrobial agent.

Genomics

The genome of C. violaceum was sequenced in 2003. It consists of a single circular chromosome of about 4.8 million base pairs. The genome contains a large number of genes involved in antibiotic production and resistance, as well as many genes involved in motility and secretion.