Genus Rahnella
Taxonomy
Morphology
Growth conditions
Biochemical characters
Ecology
Pathogenicity
References
Proteobacteria => Gammaproteobacteria => Enterobacteriales => Enterobacteriaceae => Rahnella => Rahnella aquatilis - type
species of the genus, Izard et al. 1981. Three genomospecies reported.
Gram negative rods.
Facultatively anaerobic, growth temperature 30 - 37 °C.
Nutrient agar or nutrient broth;
Trypticase Soy Agar ± 5% sheep blood.
Widely distributed in nature. Isolated from water, foods (meat, freshwater fish, dairy
products), plants, feces; from humans and animals (snails, earthworms).
Isolated from immunocompromised human patients (blood, sputum, wound & burns infections, bacteremia).
Food contaminant. Rahnella contamination has been associated with increased histamine levels in fish products.
R. aquatilis grow symbiotically in plant root nodules (nitrogen-fixing bacteria) and express a  root adhesin and pore forming 38-kDa
major outer membrane protein. As the outer membrane protein shares high sequence similarity with those of other gram-negative
pathogens, it seems possible that Rahnella's root adhesin mediates adherence to epithelial cells during bacterial invasion.
Also, O-lipopolysaccharide found to be toxic and pyogenic for experimental animals.
  1. Bergey’s Manual of Determinative Bacteriology, 9th ed., 1994;
  2. Izard D., Gavini F., Trinel P.A. & Leclerc H.: Rahnella aquatilis, nouveau membre de la famille des Enterobacteriaceae. Ann.
    Microbiol., 1979, 130A, 163-177.
  3. Brenner D.J., Muller H.E., Steigerwalt A.G., Whitney A.M., O'Hara C.M. & Kampfer P.: Two new Rahnella genomospecies that
    cannot be phenotypically differentiated from Rahnella aquatilis. Int. J. Syst. Bacteriol., 1998, 48, 141-149.
  4. Achouak, W., J.-M. Pages, R. De Mot, G. Molle, and T. Heulin. 1998. A major outer membrane protein of Rahnella aquatilis
    functions as a porin and root adhesin. J. Bacteriol. 180:909-913.
  5. Zdorovenko, E. L., L. D. Varbanets, G. V. Zatonsky, and A. N. Ostapchuk. 2004. Structure of the O-polysaccharide of the
    lipopolysaccharide of Rahnella aquatilis 1-95. Carbohydr. Res. 339:1809-1812.
  6. Varbanets, L. D., A. N. Ostapchuk, and N. V. Vinarskaia. 2004. Isolation and characterization of Rahnella aquatilis
    lipopolysaccharides. Mikrobiol. Zh. 66:25-34.
  7. Kaley Tash: Rahnella aquatilis Bacteremia from a Suspected Urinary Source. Journal of Clinical Microbiology, May 2005, p.
    2526-2528, Vol. 43, No. 5.
R. aquatilis may be confused with Enterobacter agglomerans due to similarities in the
organisms' biochemical tests. See table at the end.
The three genomospecies of Rahnella aquatilis cannot be biochemically differentiated.

 

Pigment

Catalase

Oxidase

Lactose

ONPG

Arginine dihydrolase

Lysine decarboxylase

Ornithine decarboxylase

Rahnella aquatilis

-

+

-

+

+

-

-

-

 

Indole production

Citrate utilization

Hydrogen sulfide

Urea hydrolysis

Voges-Proskauer

Phenilalanine

Motility

Gelatinase

Growth on KCN media

Malonate

-

+

-

-

+

+

-

-

-

+

 

Glucose

Gas from glucose

D-Mannitol

Inositol

D-Sorbitol

L-Rhamnose

Sucrose (Sacharose)

Melibiose

L-Arabinose

Nitrate reduction

+

+

+

-

+

+

+

+

+

+

 

Cellobiose

Dulcitol

Glycerol

Maltose

D-Mannose

Alfa-Methyl-D-Glucoside

Raffinose

Salicin

Trehalose

D-Xylose

+

[+]

[-]

+

+

-

+

+

+

+

 

Mucate

Tartrate (Jordans)

Esculin hydrolysis

Acetate utilization

Deoxyribonuclease

Lipase

Mehyl red

D-Adonitol

=

-

+

-

-

-

[+]

-
(c) Costin Stoica
Antibiogram
Encyclopedia
Culture media
Biochemical tests
Stainings
Images
Movies
Articles
Identification
Software
R E G N U M
PROKARYOTAE