Proteobacteria is a phylum of the domain Bacteria that includes a great diversity of forms of species. This phylum has six taxonomic classes: (1) Alphaproteobacteria, (2) Betaproteobacteria, (3) Gammaproteobacteria, (4) Deltaproteobacteria, (5) Epsilonproteobacteria, and (6) Zetaproteobacteria.
The class Zetaproteobacteria is the most recently described proteobacteria.1 One known species of this class is Mariprofundus ferrooxydans. This species is a chemolithoautotroph isolated from a submarine volcane, Loihi Seamount in 1996.1, 2 It grows by oxidising ferrous to ferric iron. It has a doubling time at 23°C of 12 hours and a curved rod (approximately 0.5×2–5 µm) morphology.1
1 Emerson, D., Rentz, J. A., Lilburn, T. G., Davis, R. E., Aldrich, H., Chan, C., & Moyer, C. L. (2007). Reysenbach, Anna-Louise, ed. "A Novel Lineage of Proteobacteria Involved in Formation of Marine Fe-Oxidizing Microbial Mat Communities". PLoS ONE 2 (8): e667.
1 Emerson, D. & Moyer, C. L. (2002). "Neutrophilic Fe-oxidizing bacteria are abundant at the Loihi Seamount hydrothermal vents and play a major role in Fe oxide deposition". Applied and environmental microbiology 68 (6): 3085–3093.