Paenibacillus larvae
Cultural characteristics
Biochemical characters
Phylum Firmicutes, Class Bacilli, Order Bacillales, Family Paenibacillaceae, Genus Paenibacillus, Paenibacillus larvae (White 1906;
Ash, Priest and Collins 1995; Heyndrickx, Vandemeulebroecke, Hoste, Janssen, Kersters, De Vos, Logan, Ali and Berkeley 1996)
Genersch, Forsgren, Pentikainen, Ashiralieva, Rauch, Kilwinski and Fries 2006.
Bacillus larvae White 1906 & Bacillus pulvifaciens (ex Katznelson 1950) Nakamura 1984.
Note: Recently the existence of two subspecies (P. larvae subsp. larvae  and  P. larvae subsp pulvifaciens has been reconsidered by
Genersch et al. (2006), who proposed reclassification into a single species based on a polyphasic study encompassing more
strains than the former studies and by which the former subspecies discrepancies based on PAGE profiling of cell proteins became
Gram positive, 0.3-0.7 x 1.5-6.0 µm μm bacillus. Motility is variable (11-89% of strains are motile). Motile strains produce fascicular
agglomerations of released flagella (“giant cords”) sized between 0.2 – 30 μm. Some strains synthetise zooglea.
Sporulated, with 1.1-1.3 x 0.6-0.7 μm, ellipsoidal, deforming spore, located central or sub-terminal.
Long chains or filaments, sometimes parallel.
Frequently free spores are observed in smears from dead honeybees of  ‘American foulbrood’.
Aerobic, facultative anaerobic. Requires aerobic conditions for vegetative growth and
Spores’ germination enhanced by low oxygen atmosphere.
Do not grow on simple media (nutritive broth or nutritive agar) - essential
characteristic for differentiating from other genera of Bacillus and Paenibacillus (only
P. larvae together with Paenibacillus popilliae and P. lentimorbus (two japanese  
scarabeid larvae pathogens) do not grow on simple media).
Main growth media:
- Honeybee larvae extract medium
- Nutritive broth / agar with 10% rabbit / horse serum
- BHI with 0,01% thiaminhydrochloride
- Medium with yeast extract, glucose, starch, monopotassic phosphate, agar.
Growth when subculturing in nutrient broth is variable.
Isolated from honeybees larvae dead of’ American foulbrood, from  wax, pollen, nectar, honey and all the other components the affected
During sporulation produces an antibiotic active against many Gram negative, Gram positive and acid-fast bacteria.
Natural infection: producing American foulbrood in Apis mellifera L. &  Apis cerana characterized by changes of color, consistency,
odour and volume of the larvae; followed by death.
Experimental infection: honeybee larvae only pathogen, not for other insects, mouse, rat, hamster, rabit or human etc.
Pathogenicity factors: a thermo-stable toxin, proteolytic enzymes, hemolymph & tissue multiplication.
  1. Bailey L. (1963) – Infectious disease of honey-bee. Land Books Limited, London.
  2. Gordon R.E., Haynes W.C., Pang C.H. (1973) – The genus Bacillus . Agriculture Handbook No. 427, U.S.D.A., Washington D.C.
  3. Buchanan R.E., Gibbons N.E., Cowan S.T., Holt J.G., Liston J., Murray R.G.E., Niven C.F., Ravin A.W., Stanier R.W. ( 1974) – Bergey’s
    Manual of Determinative Bacteriology, Eight Edition, The Williams & Wilkins Company, Baltimore.
  4. Sorescu Ionut (1998) – Cercetari privind raspunsul imun in principalele boli bacteriene si micotice ale albinei melifere, Apis
    mellifera L. Teza de doctorat, USAMV Bucuresti.
  5. Heyndricks M., Vandemenlebroecke K., Hoste B., Janssen P., Kersters K., De Vos P., Logan N. A., Ali N., Berkeley R.C.W. (1996)
    Reclassification of Paenibacillus (formerly Bacillus) pulvifaciens (Nakamura 1984) Ash et al. 1994, a later subjective synonym of
    Paenibacillus (formerly Bacillus) larvae  (White 1906) Ash et al. 1994, as a subspecies of P. larvae subsp. pulvifaciens. International
    J. Syst. Bact., 46, 1, 270-279.
  6. Priest F.G., 2009. Genus I. Paenibacillus Ash, Priest and Collins 1994. 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, 269-295.
  7. Genersch E., Forsgren E., Pentikainen J., Ashiralieva A., Rauch S., Kilwinski J. and Fries I., 2006.   Reclassification of Paenibacillus
    larvae subsp. pulvifaciens and Paenibacillus larvae subsp. larvae as Paenibacillus larvae without subspecies differentiation. IJSEM
    56, 501-511.
Acid is produced from: glycerol, glucose & trehalose. Acid is not produced from: L-arabinose & D-xylose.
Casein decomposition, gelatin liquefaction, lipase, H
2S production & hydrolysis of esculin  are positive.
Starch hydrolysis, phenilalanine, indole production, Voges-Proskauer, catalase, arginin-dehydrolase, ONPG, dihydroxyacetone
production, citrate utilization & degradation of tyrosine are negative.
Nitrates reduction to nitrites, alkaline phosphatase, acid phosphatase, acid production from mannitol & salicin are variable.
Soluble starch stimulates sporulation.
Growth pH: 6.6-7.4, optimal growth temperature 28-30 / 35-37 ºC (min. 25 ºC, max.
40 ºC) / 48-72 hours. Grows in 2% NaCl media, but not in 5 or 7% NaCl.
Cultural characters:
- in liquid medium:  non-uniform, moderate turbidity , deposit, some strains can form a thin, transparent film.
- on solid medium: small, 1-2 mm in dimaeter, gray / light yellow, R-type, sand-granule aspect colonies. On enriched or biphasic
medium may form large, mucous, opaque colonies because of their ability to produce (in the sporulation period) an antibiotic
substance active against many  Gram-positive / -negative bacteria. Sometimes the colonies has a bright orange pigment. Hemolysis
is usually negative.
P. larvae is isolated solely and in a pure culture from diseased / dead larvae body .
(c) Costin Stoica
Culture media
Biochemical tests
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