Bacillus polymyxa is a rod-shaped, Gram-positive bacterium that fixes nitrogen anaerobically. It measures 0.6 by 3.0 μm and forms pale colonies on agar. Reproduction involves the formation of ellipsoidal spores that cause the mother cell to swell noticeably. These endospores can germinate under favorable conditions. Spore germination can be influenced by factors such as heat activation and the presence of nutrients like fructose and L-alanine, while organic acids can impact the spores' heat resistance. In its vegetative state, P. polymyxa possesses peritrichous flagella that facilitate motility and swarming.