Chromobacterium violaceum colonies may exhibit an almond-like odor. Most strains also produce violacein, a dark violet pigment.

Why Does Chromobacterium violaceum Have an Almond-Like Odor?

The almond-like odor is associated with cyanide production during bacterial metabolism. It is distinct from the violet coloration produced by violacein.

What Is Violacein?

Violacein is a dark violet pigment that is soluble in ethanol but insoluble in water. Although most strains of C. violaceum produce this pigment, nonpigmented strains also occur. The absence of violet pigmentation therefore does not exclude the organism.

Which Other Characteristics Support Identification?

C. violaceum is a motile, facultatively anaerobic Gram-negative rod or coccobacillus. It is catalase-positive, usually oxidase-positive, glucose-fermenting, and indole-negative. Colonies may exhibit beta-hemolysis.

Identification requires interpretation of these findings alongside colony morphology and validated testing. Neither odor nor pigmentation alone establishes definitive identification.

How Does Its Odor Compare with That of Other Bacteria?

Organism	Reported odor association
Chromobacterium violaceum	Almond-like
Pseudomonas aeruginosa	Sweet, fruity, or grape-like
Eikenella corrodens	Bleach-like
Alcaligenes faecalis	Freshly cut apple-like
Stenotrophomonas maltophilia	Ammonia-like on blood agar
Proteus mirabilis and P. vulgaris	Burnt chocolate or rotten cooked fish
Clostridioides difficile	Horse-stable or manure-like

Odor descriptions may vary with culture conditions and the observer.

Laboratory Safety

Culture plates must not be deliberately sniffed. Follow established laboratory biosafety procedures and validated identification methods.