Growth of Thiobacillus ferrooxidans on Formic Acid

Abstract

A variety of acidophilic microorganisms were shown to be capable of oxidizing formate. These included Thiobacillusferrooxidans ATCC 21834, which, however, could not grow on formate in normal batch cultures. However, the organism could be grown on formate when the substrate supply was growth limiting, e.g., in formate-limited chemostat cultures. The cell densities achieved by the use of the latter cultivation method were higher than cell densities reported for growth of T. ferrooxidans on ferrous iron or reduced sulfur compounds. Inhibition of formate oxidation by cell suspensions, but not cell extracts, of formate-grown T. ferrooxiddns occurred at formate concentrations above 100 ,iM. This observation explains the inability of the organism to grow on formate in batch cultures. Cells grown in formate-limited chemostat cultures retained the ability to oxidize ferrous iron at high rates. Ribulose 1,5-bisphosphate carboxylase activities in cell extracts indicated that T. ferrooxidans employs the Calvin cycle for carbon assimilation during growth on formate. Oxidation of formate by cell extracts was NAD(P) independent.

Anaerobic Growth of Thiobacillus ferrooxidans

“…In contrast, aerobic growth yields of T. ferrooxidans on inorganic sulfur compounds are over twofold higher than the growth yield on ferrous iron (5). The cell yields observed in the present study are consistent with a model proposed previously (13) in which the ferric ironreducing enzyme system accepts electrons at the redox level of the ferrous iron oxidoreductase. However, more information about cell size and biomass composition is required before definitive conclusions can be drawn on the energetic efficiency of anaerobic growth.…”

“…Thiobacillus ferrooxidans is an obligately autotrophic, acidophilic bacterium. Autotrophic growth can be supported by the oxidation of a variety of inorganic sulfur compounds, ferrous iron (6,8), molecular hydrogen (4), or formic acid (13). T. ferrooxidans and physiologically related bacteria are of great economical importance because of their involvement in the biological leaching of copper and uranium ores and the biooxidation of gold ores (16).…”

Biodiversity and ecology of acidophilic microorganisms

“…Most iron-and sulfur-oxidising acidophiles are regarded as autotrophic, though the ability to assimilate organic carbon has been demonstrated with some of these (e.g. utilisation of formic acid by T. ferrooxidans [11]). Other prokaryotes which catalyse the dissimilatory oxidation of iron and/or RSCs are either mixotrophic (i.e.…”

Leaching of Pyrite by Acidophilic Heterotrophic Iron-Oxidizing Bacteria in Pure and Mixed Cultures

“…Two species of mesophilic acidophilic bacteria, Thiobacillus ferrooxidans and Leptospirillum ferrooxidans, have been implicated as being the most significant microorganisms involved in sulfide mineral oxidation, although moderately thermophilic (or thermotolerant) bacteria and extremely thermophilic archaea are also known to be important in certain situations, such as self-heating coal spoils and bioleaching operations in which temperatures exceed 40°C. Both T. ferrooxidans and L. ferrooxidans are generally regarded as obligate chemolithotrophs and synthesize cell carbon via enzymic fixation of CO 2 , although it has been shown that T. ferrooxidans has a limited capacity to utilize organic carbon (22). Two mechanisms ("direct" and "indirect") have been described as the mechanisms by which metal-mobilizing acidophilic bacteria degrade sulfide minerals, although electrochemical interactions which occur between minerals during bacterial leaching are also thought to be important in accelerating mineral dissolution (20).…”