Chro.mo.bac.te' ri.um.
Gr. n.
chroma
color; Gr. n.
bakterion
a small rod; M.L. neut. n.
Chromobacterium
a small, colored rod.
Proteobacteria / Betaproteobacteria / Neisseriales / Neisseriaceae / Chromobacterium
Cells straight
,
round‐ended
,
often coccoid
,
but usually occuring as rods, 0.6–0.9
×
1.5–3.0
μ
m
, occurring singly, sometimes in pairs or short chains. No definite capsules are evident. No resting stages known. Gram negative. Usually contain poly‐β‐hydroxy‐butyrate crystals (80% of strains positive), but rarely contain metachromatic granules.
Motile by means of both a single polar flagellum and, usually, one or more subpolar or lateral flagella
.
Facultative anaerobes
.
Minimum temperature for growth 10–15
°
C; maximum about 40
°
C; optimal growth at 30–35
°
C
. Optimal pH 7–8; no growth occurs below pH 5. Grow on ordinary peptone media; no distinctive organic growth factor requirements. Colonies are smooth, but rough variants may occur; colonies are of butyrous consistency and are easily emulsified in water.
Most strains produce the violet pigment violacein
, but strains producing nonpigmented colonies are sometimes encountered, and subcultures of pigmented strains often contain partially or completely unpigmented colonies. Growth in nutrient broth produces a violet ring at the surface with a fragile pellicle. Chemoorganotrophs;
most strains
(
80
%)
attack carbohydrates fermentatively, some
(
20
%)
oxidatively, producing small amounts of acid
but usually no gas. Lactate is oxidized to CO
2
. Usually oxidase positive by the method of Sivendra and Lo (1975). No growth in media containing 6% or more NaCl. Catalase positive, but very sensitive to hydrogen peroxide. Indole negative, Voges–Proskauer negative. Nitrate and nitrite reduced. Ammonia produced from peptone. Arginine hydrolyzed.
Hydrogen cyanide produced
.
Resistant to benzylpenicillin
, 10 mg/ml.
Sensitive to tetracycline
, 30 mg/ml.
Resistant to O
/
129
(
2
,
4‐diamino‐6
,
7‐diisopropyl pteridine
) by disc diffusion method, 50 mg/disc. Soil and water organisms, occasionally causing infections of humans and other mammals. 16S rRNA gene sequence data place
Chromobacterium
in the class
Betaproteobacteria
.
The mol
%
G
+
C of the DNA is
: 65–68 (
T
m
).
Type species
:
Chromobacterium violaceum
Bergonzini 1881, 153.