Kinetics of anaerobic elemental sulfur oxidation by ferric iron in Acidithiobacillus ferrooxidans and protein identification by comparative 2-DE-MS/MS

Abstract

Elemental sulfur oxidation by ferric iron in Acidithiobacillus ferrooxidans was investigated. The apparent Michaelis constant for ferric iron was 18.6 mM. An absence of anaerobic ferric iron reduction ability was observed in bacteria maintained on elemental sulfur for an extended period of time. Upon transition from ferrous iron to elemental sulfur medium, the cells exhibited similar kinetic characteristics of ferric iron reduction under anaerobic conditions to those of cells that were originally maintained on ferrous iron. Nevertheless, a total loss of anaerobic ferric iron reduction ability after the sixth passage in elemental sulfur medium was demonstrated. The first proteomic screening of total cell lysates of anaerobically incubated bacteria resulted in the detection of 1599 protein spots in the master two-dimensional electrophoresis gel. A set of 59 more abundant and 49 less abundant protein spots that changed their protein abundances in an anaerobiosis-dependent manner was identified and compared to iron- and sulfur-grown cells, respectively. Proteomic analysis detected a significant increase in abundance under anoxic conditions of electron transporters, such as rusticyanin and cytochrome c(552), involved in the ferrous iron oxidation pathway. Therefore we suggest the incorporation of rus-operon encoded proteins in the anaerobic respiration pathway. Two sulfur metabolism proteins were identified, pyridine nucleotide-disulfide oxidoreductase and sulfide-quinone reductase. The important transcription regulator, ferric uptake regulation protein, was anaerobically more abundant. The anaerobic expression of several proteins involved in cell envelope formation indicated a gradual adaptation to elemental sulfur oxidation.

Comparison of environmental and isolate Sulfobacillus genomes reveals diverse carbon, sulfur, nitrogen, and hydrogen metabolisms

“…Although Fe 3+ reduction is widespread in acidophilic microorganisms [ 95 , 96 ], little is known about the precise enzymes and pathways involved. In A. ferroxidans, a c -type cytochrome has been implicated in ferric iron respiration [ 97 ] as has a rusticyanin [ 98 ]. Rusticyanin proteins are found annotated only in S. thermosulfidooxidans and AMDSB5, and membrane-bound c- type cytochrome proteins are found in all Sulfobacillus genomes except AMDSBA1.…”

Biodiversity, metabolism and applications of acidophilic sulfur‐metabolizing microorganisms

“…ferrooxidans showed upregulation of sulfide/quinone oxidoreductase ( sqr ) and proteins involved in cell envelope biogenesis (Kucera et al ., 2012). In addition, proteins previously attributed to electron transport during aerobic Fe 2+ oxidation, including rusticyanin and cytochrome c 552 , were also found to be upregulated (Kucera et al ., 2012). This observation has been confirmed in a combined proteomic and transcriptomic study of S ° ‐grown At.…”

Anaerobic Sulfur Metabolism Coupled to Dissimilatory Iron Reduction in the Extremophile Acidithiobacillus ferrooxidans

“…Tetrathionate reductase (TetH) (28) and ArsH (29) have been proposed to be candidates for the final electron donor to Fe 3ϩ . In addition, Kucera et al (30) found a significant increase in the abundance of electron transporters, such as rusticyanin and cytochrome c 552 (which are known to be involved in Fe 2ϩ oxidation), in cultures of A. ferrooxidans grown anaerobically on Fe 3ϩ . These authors suggested that rus operon-encoded proteins were involved in both Fe 2ϩ oxidation and Fe 3ϩ reduction in this acidophile.…”