Phylum Firmicutes, Class Clostridia, Order Clostridiales, Family Clostridiaceae, Genus Clostridium, Cluster XIX (Clostridium non
sensu stricto), Clostridium rectum (Heller 1922) Holdeman and Moore 1972.
This species is clearly unrelated to the genus Clostridium as it shows highest 16S
rRNA gene sequence similarity with species of the genus Fusobacterium. The closest
relative based on 16S rRNA gene sequence similarity is Fusobacterium necrogenes
(99.8%). This species should be reclassified to the genus Fusobacterium.
Historical synonyms: Hiblerillus rectus Heller 1922, Inflabilis rectus (Heller) Prevot
Gram-positive straight rods, 0.5-1.1 x 1.6-3.1 µm, and occur singly or in pairs.
Non-motile. Spores are oval, subterminal, and swell the cell; sporulation occurs most
readily in chopped-meat broth cultures.
Surface colonies on blood agar plates are pinpoint,1 mm in diameter, translucent to
semiopaque, convex, grayish white, shiny, and smooth, with entire margins and no visible internal structure; they may be slightly beta-
hemolytic. Cultures in PYG broth are turbid with a smooth sediment and have a pH of 5.2-5.7 after incubation for one week. Growth is
inhibited by 6.5% NaCl. Grow in 20% bile. Optimum temperature for growth is 37-45 ºC. Can grow at 25 ºC. Products in PYG broth:
butyric acid and abundant hydrogen. Abundant gas is detected in PYG deep agar cultures.
Isolated from horse manure, beet rhizosphere and rice paddy soil.
The type strain is susceptible to chloramphenicol, clindamycin, penicillin G, and tetracycline, but resistant to erythromycin.
Culture supernatants are not toxic to mice. Toxin is not produced.
- 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,
- Smith L.D.S. and Hobbs G., 1974. Genus III. Clostridium Prazmowski 1880. In: (Eds.) Buchanan R.E. and Gibbons N.E., Bergey’s
Manual of Determinative Bacteriology, Eighth Edition, The Williams & Wilkins Company, Baltimore, 551-572.
Milk reaction is positive (curd production). Meat is not digested.
Positive results for ammonia production, esculin hydrolysis, H2S production, neutral red reduction, resazurin reduction, substrate
utilization and/or acid production from: galactose (weak), glucose, lactose, salicin (weak) & sucrose.
Negative results for casein hydrolysis, gelatin hydrolysis, indole production, lecithinase, lipase, starch hydrolysis, urease, Voges -
Proskauer reaction, substrate utilization and/or acid production from: adonitol, amygdalin, arabinose, cellulose, dulcitol, erythritol,
esculin, glycogen, glycerol, inositol, inulin, mannitol, melezitose, melibiose, rhamnose, ribose, sorbitol, sorbose, trehalose & xylose.
Variable results for nitrate reduction, substrate utilization and/or acid production from: cellobiose, fructose, maltose, mannose,
raffinose & starch.
(c) Costin Stoica