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Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

Gloria Levicán14, Juan A Ugalde25, Nicole Ehrenfeld16, Alejandro Maass23 and Pilar Parada1*

Author Affiliations

1 Biosigma 'S.A.', Loteo Los Libertadores, Lote 106, Colina, Chile

2 Laboratory of Bioinformatics and Mathematics of the Genome, Center for Mathematical Modeling, Faculty of Mathematical and Physical Sciences, Avda Blanco Encalada 2120, 7th Floor, University of Chile, Santiago, Chile

3 Department of Mathematical Engineering and Center for Mathematical Modeling (UMI 2807, CNRS), Faculty of Mathematical and Physical Sciences, Avda Blanco Encalada 2120, 7th Floor, University of Chile, Santiago, Chile

4 Biology Department, Chemistry and Biology Faculty, University of Santiago of Chile, Avda. Libertador Bernardo O'Higgins 3363, Estación Central, Santiago, Chile

5 Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0208, USA

6 Austral Biotech, Francisco Noguera 41, Piso 3, Providencia, Santiago, Chile

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BMC Genomics 2008, 9:581  doi:10.1186/1471-2164-9-581

Published: 3 December 2008



Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments.


In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air.


The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.