Article

Microarray and bioinformatic analyses suggest models for carbon metabolism in the autotroph Acidithiobacillus ferrooxidans

University of Illinois, Chicago, USA
Hydrometallurgy (Impact Factor: 2.22). 09/2006; DOI: 10.1016/j.hydromet.2006.03.029

ABSTRACT Acidithiobacillus ferrooxidans is a chemolithoautotrophic bacterium that uses iron or sulfur as an energy and electron source. Bioinformatic analysis of the A. ferrooxidans draft genome sequence was used to identify putative genes and potential metabolic pathways involved in CO2 fixation, 2P-glycolate detoxification, carboxysome formation and glycogen utilization. Microarray transcript profiling was carried out to compare the relative expression of the predicted genes of these pathways when the microorganism was grown in the presence of iron versus sulfur. Several gene expression patterns were confirmed by real-time PCR. Genes for each of the above-predicted pathways were found to be organized into discrete clusters. Clusters exhibited differential gene expression depending on the presence of iron or sulfur in the medium. Concordance of gene expression within each cluster suggested that they are operons. Most notably, clusters of genes predicted to be involved in CO2 fixation, carboxysome formation, 2P-glycolate detoxification and glycogen biosynthesis were upregulated in sulfur medium, whereas genes involved in glycogen utilization were preferentially expressed in iron medium. These results can be explained in terms of models of gene regulation that suggest how A. ferrooxidans can adjust its central carbon management to respond to changes in its environment.

1 Bookmark
 · 
105 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biochemical and biotechnological aspects of aeration conditions in iron- and sulfur oxidizing Acidithiobacillus ferrooxidans cultures were studied. The critical values of volumetric oxygen transfer coefficient (kLa)crit and oxygen concentration (Ccrit) were used to define the conditions necessary for minimum aeration and to eliminate potential oxygen limitation during substrate oxidation by the model bioleaching culture. The Michaelis constants for oxygen were 1.07 and 0.61 μmol O2 l- 1 for the oxidation of ferrous iron and elemental sulfur, respectively. The Ccrit values, below which oxygen limitation may occur, were 6.250 and 3.125 μmol O2 l- 1, determined in respirometric experiments for the oxidation of ferrous iron and elemental sulfur, respectively. The rates of iron and sulfur oxidation were also determined at the Ccrit values by measuring the formation of ferric iron and protons in the corresponding cell suspensions. Neither iron nor sulfur oxidation was limited by oxygen at Ccrit. The (kLa)crit values required to maintain oxygen-unlimited oxidation of ferrous iron and elemental sulfur were 7.70 and 4.88 h- 1, respectively.
    Hydrometallurgy 12/2014; DOI:10.1016/j.hydromet.2014.09.009 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Draft genome sequences of Acidthiobacillus thiooxidans and A. caldus have been annotated and compared to the previously annotated genome of A. ferrooxidans. This has allowed the prediction of metabolic and regulatory models for each species and has provided a unique opportunity to undertake comparative genomic studies of this group of related bioleaching bacteria. In this paper, the presence or absence of predicted genes for eleven metabolic processes, electron transfer pathways and other phenotypic characteristics are reported for the three acidithiobacilli: CO2 fixation, the TCA cycle, sulfur oxidation, sulfur reduction, iron oxidation, iron assimilation, quorum sensing via the acyl homoserine lactone mechanism, hydrogen oxidation, flagella formation, Che signaling (chemotaxis) and nitrogen fixation. Predicted transcriptional and metabolic interplay between pathways pinpoints possible coordinated responses to environmental signals such as energy source, oxygen and nutrient limitations. The predicted pathway for nitrogen fixation in A. ferrooxidans will be described as an example of such an integrated response. Several responses appear to be especially characteristic of autotrophic microorganisms and may have direct implications for metabolic processes of critical relevance to the understanding of how these microorganisms survive and proliferate in extreme environments, including industrial bioleaching operations.
    Hydrometallurgy 11/2008; 94(1-4):180-184. DOI:10.1016/j.hydromet.2008.05.039 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Draft genome sequences of Acidithiobacillus thiooxidans ATCC 19377 and A. caldus ATCC 51756 have been annotated. Bioinformatic analysis of these two new genomes, together with that of A. ferrooxidans ATCC 23270, allows the prediction of metabolic and regulatory models for each species and has provided a unique opportunity to undertake comparative genomic studies of this group of bioleaching bacteria. In this paper, we report preliminary information on metabolic and electron transfer pathways for ten characteristics of the three acidithiobacilli: CO2 fixation, the TCA cycle, sulfur oxidation, sulfur reduction, iron oxidation, iron assimilation, hydrogen oxidation, flagella formation, Che signaling (chemotaxis) and nitrogen fixation. Predicted transcriptional and metabolic interplay between pathways pinpoints potential coordinated responses to environmental signals such as energy source, oxygen and nutrient limitations. The predicted pathway for nitrogen fixation in A. ferrooxidans will be described as an example of such an integrated response. Several responses appear to be especially characteristic of autotrophic microorganisms and may have direct implications for metabolic processes of critical relevance to the understanding of how these microorganisms survive and proliferate in extreme environments, including industrial bioleaching operations.
    Advanced Materials Research 07/2007; 20-21:439-442. DOI:10.4028/www.scientific.net/AMR.20-21.439

Full-text (4 Sources)

Download
73 Downloads
Available from
Jun 2, 2014