Collected together under this heading are several genera of aerobic (mostly mi-croaerophilic) spiral-shaped bacteria with polar flagella. These include free-living, sym-biotic and parasitic types.
Spirilla such as Aquaspirillum and Magnetospirillum contain magnetosomes, intra-cellular particles of iron oxide (magnetite, Fe3O4). Such magnetotactic bacteria have the remarkable ability to orientate themselves with respect to the earthâ€™s magnetic field (magnetotaxis).
Two important pathogens of humans are included in the spirilla; Campylobacterjejuni is responsible for foodborne gastroenteritis, while Helicobacter pylori has in recenttimes been identified as the cause of many cases of peptic ulcers.
Representative genera: Magnetospirillum, Campylobacter