Microaerophile

Microaerophilic organisms are a specific type of organism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere (~20% concentration).

Examples include Borrelia burgdorferi, a species of spirochaete bacteria that causes Lyme disease in humans, and Helicobacter pylori, a species of proteobacteria that has been linked to peptic ulcers and some types of gastritis.