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Bacillus subtilis
Bacillus subtilis Bacillus subtilis
Initially the colonies are small and mucoid, but quickly become medium-sized. The surface of the colonies dries out and become wrinkled. Underneath, the surface the colonies may be mucoid or dry. The colonies adhere to the agar and appear brownish or greenish, although the wrinkles are lighter in colour.

Close-up picture of the same plate
The same Blood Agar plate examined with transmitted light. The colonies are surrounded by a zone of unspecific lysis caused by enzymatic activity. This is particularly clear in areas where the colonies lie closely together because the concentration of enzymes is high. Around small colonies that lie alone, this lysis may not be visible due to the low concentration of enzymes.
General characteristics: Gram-positive, long rods with a diameter < 0.9 µm. Catalase-positive. Attacks sugars by fermentation. Motile.
© Department of Veterinary Disease Biology 2011
Faculty of Health and Medical Sciences - University of Copenhagen