Morphological Variation in Ferrobacillus Ferrooxidans related to the Rate of Iron Oxidation

Abstract

WHILE investigating the removal of pyritic sulphur from coal by a microbiological method, we propagated large numbers of the chemoautotrophic iron-oxidizing bacterium Ferrobacillus ferrooxidans. During mass culture of the bacterium in an inorganic iron salts medium (9K)¹, it was observed that alterations in cellular morphology occurred in response to excessively vigorous aeration. Normal cells measure 1.0–1.7µ by 0.5µ (Fig. 1A), while the abnormal (morphologically altered) cells differed by having a diameter of 1.0µ, so that many enlarged, coccoidal forms were present (Fig. 1B). The abnormal strain, on large-scale sub-culture using less vigorous aeration, or in shake-culture flasks, showed virtually complete reversion to the normal morphology after the second transfer (Fig. 1C, D).