They complete the oxidation of partially oxidized iron compounds and are able to couple the energy produced to the synthesis of carbohydrate. This provides the energy to drive their anabolic reactions. The nitrates produced as a byproduct supply the nitrogen needs of plants. Link to discussion of the various roles that bacteria play in the nitrogen cycle. Clostridium tetani .
Clostridia are spore-forming obligate anaerobes .
The spores of C. tetani are widespread in the soil and often get into the body through wounds. C. tetani liberates a toxin that blocks inhibitory synapses in the spinal cord and brain. This interferes with the reciprocal inhibition of antagonistic pairs of skeletal muscles so the victim suffers violent muscle spasms. Chemical alteration of the toxin produces a toxoid that still retains the epitopes of the toxin. Clostridium botulinum .