Periplasmic Proteins of the Extremophile Acidithiobacillus ferrooxidans

Abstract

Acidithiobacillus ferrooxidans is a chemolithoautotrophic acidophile capable of obtaining energy by oxidizing ferrous iron or sulfur compounds such as metal sulfides. Some of the proteins involved in these oxidations have been described as forming part of the periplasm of this extremophile. The detailed study of the periplasmic components constitutes an important area to understand the physiology and environmental interactions of microorganisms. Proteomics analysis of the periplasmic fraction of A. ferrooxidans ATCC 23270 was performed by using high resolution linear ion trap-FT MS. We identified a total of 131 proteins in the periplasm of the microorganism grown in thiosulfate. When possible, functional categories were assigned to the proteins: 13.8% were transport and binding proteins, 14.6% were several kinds of cell envelope proteins, 10.8% were involved in energy metabolism, 10% were related to protein fate and folding, 10% were proteins with unknown functions, and 26.1% were proteins without homologues in databases. These last proteins are most likely characteristic of A. ferrooxidans and may have important roles yet to be assigned. The majority of the periplasmic proteins from A. ferrooxidans were very basic compared with those of neutrophilic microorganisms such as Escherichia coli, suggesting a special adaptation of the chemolithoautotrophic bacterium to its very acidic environment. The high throughput proteomics approach used here not only helps to understand the physiology of this extreme acidophile but also offers an important contribution to the functional annotation for the available genomes of biomining microorganisms such as

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

“…S2 in the supplemental material). OMPP1/ FadL/TodX family proteins have been demonstrated to be located in the outer membrane (A. Yarzábal and V. Bonnefoy, unpublished data) and to be upregulated during aerobic S 0 metabolism compared to during Fe 2ϩ oxidation (19,60). The gene encoding survival protein A (surA [AFE_3035]), which is required for correct folding of outer membrane proteins (61), was also upregulated under anaerobic conditions.…”

“…One strain of A. ferrooxidans has been reported to couple the oxidation of H 2 to the reduction of S 0 (12), and the type strain genome contains genes predicted to encode hydrogenases and a S 0 reductase (15) that have both been biochemically characterized (16)(17)(18). Models for substrate oxidation and energy conservation during aerobic growth of A. ferrooxidans on either Fe 2ϩ or inorganic sulfur compounds have been developed on the basis of functional genomic approaches (15,(19)(20)(21) as well as molecular genetics and biochemical methods (reviewed in references 3 and 21 to 23). In contrast, relatively little is known about the mechanism of Fe 3ϩ reduction in acidophiles.…”

Tetrathionate-Forming Thiosulfate Dehydrogenase from the Acidophilic, Chemolithoautotrophic Bacterium Acidithiobacillus ferrooxidans

“…Although the involvement of AFE_0042 in sulfur metabolism has been suggested, its actual function has not been fully determined. The periplasmic localization of AFE_0042 (HypA1) has been reported elsewhere (44).…”

Cytoplasmic CopZ-Like Protein and Periplasmic Rusticyanin and AcoP Proteins as Possible Copper Resistance Determinants in Acidithiobacillus ferrooxidans ATCC 23270

“…The encoded proteins could bind to copper in the periplasm and deliver it to the CusCBA system that mediates the efflux of this metal to the extracellular space (20,21). The other copper chaperone present in the periplasm of A. ferrooxidans is CopC Af (21,22), an ortholog of PcoC from E. coli (9) and CopC from Pseudomonas syringae (23).…”