Depolarizationof the axon hillock to threshold results in the generationand propagation of an action potential. The action poten-tial is a transient change in the membrane potential charac-terized by a gradual depolarization to threshold, a rapid ris-ing phase, an overshoot, and a repolarization phase.
Ecology. Staphylococcus aureus is a normal inhabitant of the skin and mucous membranes in the nose of a healthy human, while S. epidermidis inhabits only the skin of healthy humans. S. aureus is infectious to both animals and humans.he Staphylococcus aureus genome, which is the most common species amoung the genome projects, is about 2.8 Mega-base pairs long with approximately 2,600 open reading frames, comprising 84.5% of the genome.
As obligate anaerobes, Clostridium botulinum must live in low oxygen habitats, as higher concentrations are toxic to the cells. These bacteria live in relatively neutral environments and have the most successful growth rates in a pH ranging from 4.6-7.0. Clostridium botulinum is most commonly found as an inactive spore in the shape of an oval. The spores generate a tough outer protective coating and several layers of membranes to enclose the cell and keep it alive. Most Clostridium botulinum spores reside on the surfaces of fruits, dairy products, vegetables, seafood, and various canned foods.