Cultural characteristics
Biochemical characters
Phylum Firmicutes, Class Clostridia, Order Clostridiales, Family Clostridiaceae, Genus Clostridium, Cluster XIVa (non-Clostridium
sensu stricto),
Clostridium symbiosum  (Stevens 1956) Kaneuchi, Watanabe, Terada, Benno and Mitsuoka 1976.

Historical synonyms:
Bacteroides symbiosus  Stevens 1956, Fusobacterium symbiosum  (Stevens 1956) Moore and Holdeman 1972.
Gram-negative, straight rods, 0.5-0.6 x 1.5-2.0 µm, occur singly, in pairs, or in chains
Motility is variable (peritrichous). Spores are round or oval, and subterminal.
Colonies on Eggerth–Gagnon agar after 3 days of incubation are minute - 1.0 mm in
diameter, circular, entire, low convex, smooth (sometimes with a slightly irregular
surface and margin), translucent, grayish to whitish, and have a whitish-gray or
reddish mottled center when viewed through a dissecting microscope. On blood agar,
strains may be slightly beta-hemolytic. Obligately anaerobic.
Cultures in PY-Fildes solution-glucose broth are turbid with a smooth sediment,
abundant gas, and have a pH of 5.3–6.0 after 10 days incubation.
Optimum temperature for growth is 37 ºC. Variable growth at 25 and 45 ºC. Growth is
stimulated by a fermentable carbohydrates. Growth is inhibited by 20% bile or 6.5%
NaCl. Large amounts of acetic acid, butyric acid, and lactic acid are produced in PYG
broth; abundant hydrogen is produced.
Isolated from feces of healthy humans, liver abscesses and blood infections in humans, occasionally from human infections derived
from the bowel flora. Spores survive heating to 70 ºC for 10 min but may not survive 80 ºC for 10 minutes.
Phage-like particles have been demonstrated from a strain of
Clostridium symbiosum.
Is symbiote for cultivation of Entamoeba histolytica.
Isolated from liver abscesses and blood infections in humans, occasionally from human infections derived from the bowel flora.
  1. N.A. Logan and P. De Vos, 2009. Genus I. Clostridium Prazmowski 1880. In: (Eds.) P.D. Vos, G. Garrity, D. Jones, N.R. Krieg, W.
    Ludwig, F.A. Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3: The Firmicutes,
    Springer, 738-828.
  2. Moore W.E.C. and Holdeman L.V. 1974. Genus II. Fusobacterium Knorr 1922. In: (Eds.) Buchanan R.E. and Gibbons N.E., Bergey’
    s Manual of Determinative Bacteriology, Eighth Edition , The Williams & Wilkins Company, Baltimore, 404-416.
  3. Kaneuchi C., Watanabe K., Terada A., Benno Y., and Mitsuoka T., 1976. Taxonomic study of Bacteroides clostridiiformis subsp.
    clostridiiformis (Burri and Ankersmit) Holdeman and Moore and of related organisms: proposal of Clostridium clostridiiformis
    (Burri and Ankersmit) comb. nov. and Clostridium symbiosum (Stevens) comb. nov. IJSB vol. 26, no. 2, 195-204.
Milk reaction is variable. No meat digestion.

Positive results for ammonia production, hydrogen production, H
2S production (weak), neutral red reduction, substrate utilization
and/or acid production from: fructose, galactose & glucose.

Negative results for esculin hydrolysis, hippurate hydrolysis, indole production, lecithinase, lipase, nitrate reduction, starch hydrolysis,
substrate utilization and/or acid production from: amygdalin, cellobiose, glycogen, glycerol, inositol, inulin, maltose, melezitose,
melibiose, raffinose, rhamnose, ribose, salicin, sorbitol, sorbose, starch, sucrose, trehalose & xylose.

Variable results for resazurin reduction, hydrolysis of gelatin (weak), Voges-Proskauer, substrate utilization and/or acid production
from: arabinose, lactose, mannitol & mannose.
Clostridium symbiosum
(c) Costin Stoica
Culture media
Biochemical tests
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