||P.182 left column 2nd paragraph: "Moreover, the energetics of iron reduction and oxidation at neutral pH differ substantially from those in the acidic range: whereas at pH values below 2.5, the standard redox potential of the redox pair Fe3+/Fe2+ is +770 mV, iron transformation at neutral pH involves several different iron species of various redox potentials (Table 1). Therefore, it is not surprising that iron reduction and iron oxidation at acidic and at neutral pH are carried out by different organisms because they deal with basically different chemical species as redox substrates." P.182 left column bottom paragraph: "Most iron chelates do not occur as such in the environment and exhibit redox potentials quite different from those of ferric iron oxides found in nature (Table 1). Thus, such complexes may act only as models for the natural situation, and it is necessary to know the limitations of each experimental model system." P.184 right column 2nd paragraph: "Ferrous iron can be oxidized anaerobically also in the dark, with nitrate as the electron acceptor [refs 13, 35]. At pH 7.0, all redox pairs of the nitrate reduction pathway are much more positive (E0’ values: NO3- /NO2- , +430 mV. NO2-/NO, +350 mV. NO/N2O, +1180 mV. N2O/N2, +1350 mV [ref 36]) than the redox pair ferric/ferrous iron (Table 1) and are therefore favorable electron acceptors for ferrous iron oxidation." Footnote 'a' beneath table: "At pH 7.0 and 25 degrees celsius. Redox potentials depend strongly on pH value, temperature, concentration of reactants, and thermodynamic data chosen for calculations. For details see related references."