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ABSTRACT: Acidithiobacillus ferrooxidans is a chemolithoautrophic, mesophilic Gram-negative bacterium able to oxidize ferrous iron, sulfur and metal sulfides. It forms monolayer biofilms where extracellular polymeric substances (EPS) are essential for cell attachment and metal sulfide leaching. High throughput proteomics has been applied to study the early process of biofilm formation on pyrite by At. ferrooxidans ATCC 23270. After 24h contact with the mineral, planktonic and sessile (biofilm) cell subpopulations were separated and proteins extracted. In total, 1319 proteins were detected in both samples. 62 of these were found to be increased in biofilms. Additionally, 25 proteins were found to be decreased in the biofilm cell subpopulation. 3 transcriptional factors were found to be increased or decreased among both cell subpopulations, suggesting their potential involvement in the regulation of these processes. Although no significant differences were observed for the known proteins related to ferrous iron and sulfur oxidation pathways among both cell subpopulations, the results presented here show that the early steps of At. ferrooxidans biofilm formation consist of a set of metabolic adaptations following cell attachment to the mineral surface. Functions such as EPS biosynthesis seem to be pivotal. This first high throughput proteomic study may also contribute to the annotation of several unknown At. ferrooxidans proteins found.
Proteomics 01/2013; · 4.43 Impact Factor
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Alex González,
Sören Bellenberg,
Sigde Mamani,
Lina Ruiz,
Alex Echeverría,
Laurent Soulère,
Alain Doutheau,
Cecilia Demergasso,
Wolfgang Sand,
Yves Queneau, Mario Vera,
Nicolas Guiliani
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ABSTRACT: Biofilm formation plays a pivotal role in bioleaching activities of bacteria in both industrial and natural environments. Here, by visualizing attached bacterial cells on energetic substrates with different microscopy techniques, we obtained the first direct evidence that it is possible to positively modulate biofilm formation of the extremophilic bacterium Acidithiobacillus ferrooxidans on sulfur and pyrite surfaces by using Quorum Sensing molecules of the N-acylhomoserine lactone type (AHLs). Our results revealed that AHL-signaling molecules with a long acyl chain (12 or 14 carbons) increased the adhesion of A. ferrooxidans cells to these substrates. In addition, Card-Fish experiments demonstrated that C14-AHL improved the adhesion of indigenous A. ferrooxidans cells from a mixed bioleaching community to pyrite. Finally, we demonstrated that this improvement of cell adhesion is correlated with an increased production of extracellular polymeric substances. Our results open up a promising means to develop new strategies for the improvement of bioleaching efficiency and metal recovery, which could also be used to control environmental damage caused by acid mine/rock drainage.
Applied Microbiology and Biotechnology 07/2012; · 3.42 Impact Factor
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ABSTRACT: The chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans is of great importance in biomining operations. During the bioleaching of ores, microorganisms are subjected to a variety of environmental stresses and to the limitations of some nutrients, such as inorganic phosphate (P(i)), which is an essential component for all living cells. Although the primary source of phosphorus for microorganisms is P(i), some bacteria are also able to metabolize P(i) esters (with a C-O-P bond) and phosphonates (with a very inert C-P bond). By using bioinformatic analysis of genomic sequences of the type strain of A. ferrooxidans (ATCC 23270), we found that as part of a Pho regulon, this bacterium has a complete gene cluster encoding C-P lyase, which is the main bacterial enzyme involved in phosphonate (Pn) degradation in other microorganisms. A. ferrooxidans was able to grow in the presence of methyl-Pn or ethyl-Pn as an alternative phosphorus source. Under these growth conditions, a great reduction in inorganic polyphosphate (polyP) levels was seen compared with the level for cells grown in the presence of P(i). By means of reverse transcription-PCR (RT-PCR), DNA macroarrays, and real-time RT-PCR experiments, it was found that A. ferrooxidans phn genes were cotranscribed and their expression was induced when the microorganism was grown in methyl-Pn as the only phosphorus source. This is the first report of phosphonate utilization in a chemolithoautotrophic microorganism. The existence of a functional C-P lyase system is a clear advantage for the survival under P(i) limitation, a condition that may greatly affect the bioleaching of ores.
Applied and environmental microbiology 04/2008; 74(6):1829-35. · 3.69 Impact Factor
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ABSTRACT: Acidithiobacillus ferrooxidans is one of the main acidophilic chemolithotrophic bacteria involved in the bioleaching of metal sulfide ores. The bacterium-mineral interaction requires the development of biofilms, whose formation is regulated in many microorganisms by type AI-1 quorum sensing. Here, we report the existence and characterization of a functional type AI-1 quorum-sensing system in A. ferrooxidans. This microorganism produced mainly acyl-homoserine lactones (AHL) with medium and large acyl chains and different C-3 substitutions, including 3-hydroxy-C8-AHL, 3-hydroxy-C10-AHL, C12-AHL, 3-oxo-C12-AHL, 3-hydroxy-C12-AHL, C14-AHL, 3-oxo-C14-AHL, 3-hydroxy-C14-AHL, and 3-hydroxy-C16-AHL. A quorum-sensing genetic locus that includes two open reading frames, afeI and afeR, which have opposite orientations and code for proteins with high levels of similarity to members of the acyl synthase (I) and transcriptional regulator (R) protein families, respectively, was identified. Overexpression of AfeI in Escherichia coli and the associated synthesis of AHLs confirmed that AfeI is an AHL synthase. As determined by reverse transcription-PCR, the afeI and afeR genes were transcribed in A. ferrooxidans. The transcription levels of the afeI gene were higher in cells grown in sulfur and thiosulfate media than in iron-grown cells. Phosphate starvation induced an increase in the transcription levels of afeI which correlated with an increase in AHL levels. Two afe boxes which could correspond to the AfeR binding sites were identified upstream of the afeI gene. This is the first report of a functional type AI-1 quorum-sensing system in an acidophilic chemolithotrophic microorganism, and our results provide a very interesting opportunity to explore the control and regulation of biofilm formation during the bioleaching process.
Applied and Environmental Microbiology 12/2005; 71(11):7033-40. · 3.83 Impact Factor
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ABSTRACT: Eight nucleotide sequences containing a single rhodanese domain were found in the Acidithiobacillus ferrooxidans ATCC 23270 genome: p11, p14, p14.3, p15, p16, p16.2, p21, and p28. Amino acids sequence comparisons allowed us to identify the potentially catalytic Cys residues and other highly conserved rhodanese family features in all eight proteins. The genomic contexts of some of the rhodanese-like genes and the determination of their expression at the mRNA level by using macroarrays suggested their implication in sulfur oxidation and metabolism, formation of Fe-S clusters or detoxification mechanisms. Several of the putative rhodanese genes were successfully isolated, cloned and overexpressed in E. coli and their thiosulfate:cyanide sulfurtransferase (TST) and 3-mercaptopyruvate/cyanide sulfurtransferase (MST) activities were determined. Based on their sulfurtransferase activities and on structural comparisons of catalytic sites and electrostatic potentials between homology- modeled A. ferrooxidans rhodaneses and the reported crystal structures of E. coli GlpE (TST) and SseA (MST) proteins, two of the rhodanese-like proteins (P15 and P16.2) could clearly be defined as TSTs, and P14 and P16 could possibly correspond to MSTs. Nevertheless, several of the eight A. ferrooxidans rhodanese-like proteins may have some different functional activities yet to be discovered.
Omics A Journal of Integrative Biology 02/2005; 9(1):13-29. · 2.44 Impact Factor
