The majority are purple nonsulfur bacteria, producing energy through photosynthesis; originally all purple nonsulfur bacteria were included here.

[4][5] They are often found in anaerobic aquatic environments, such as mud and stagnant water, although they are able to survive in air.

[4] This family also includes Magnetospirillum, which contains tiny chains of magnetite.

[4] These let it sense the Earth's magnetic field, which runs downwards as well as north or south, to return to the bottom of a pond (magnetotaxis).

Similar magnetite chains found in Martian meteorites have been suggested as evidence of life on Mars.