TRANSFORMATION OF TRIVALENT IRON COMPOUNDS BY LEPTOTHRIX-PSEUDOOCHRACEA

Using Mossbauer spectroscopy and magnetic measurements the action of the bacterium Leptothrix pseudoochracea on iron(III)-citrate and FeCl3 was studied. It was shown that the bacteria accumulate paramagnetic, diamagnetic, and dispersed magnetically ordered compounds during batch cultivation in the presence of a low level of aeration in a medium containing Fe(III)-citrate and a medium containing FeCl3 as the sole iron source. The diamagnetic compounds, which constitute 40% and 65% of the above-mentioned types of compounds in citrate and chloride medium respectively, are associated mainly with the cell surface. The iron compounds accumulated by the bacteria include two forms of Fe(III) compounds, iron hydroxides, and the mineral ferrihydrite, and two forms of Fe(II) compounds (when grown in glucose- and iron-supplemented medium) consisting of Fe(II)-organic coordination compounds. A scheme indicating the transformation pathways of trivalent iron by L. pseudoochracea is proposed.