Invited commentary: lubricating the rusty wheel,new insights into iron oxidizing bacteria through comparative genomics

A commentary on: Comparative genomics of freshwater Fe-oxidizing bacteria: implications for physiology, ecology, and systematics by Emerson, D., Field, E. K., Chertkov, O., Davenport, K. W., Goodwin, L., Munk, C., et al. Front. Microbiol. 4:254. doi: 10.3389/fmicb.2013.00254 Iron is the fourth most abundant mineral in the Earth's lithosphere (Weber et al., 2006; Emerson et al., 2013), where it is present at a mean concentration of 5% (Hedrich et al., 2011). Iron can exist in two oxidation stages as ferrous (Fe(II)) and ferric (Fe(III)) iron and some bacteria and archaea have evolved to use iron as an obligate or facultative energy source, giving them the name “Iron Oxidizing Bacteria” (FeOB) and “Iron Oxidizing Archaea” (FeOA), respectively (Figure 1). The oxidation from Fe(II) to Fe(III) can occur under both oxic and anoxic conditions within a pH range between 0.5 to 8.4 (Edwards et al., 2000; Weber et al., 2006; Hedrich et al., 2011). Here, the microbially mediated oxidation of iron under (micro-)aerobic circum-neutral conditions will be discussed.