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International Journal of Evolutionary Biology
Volume 2011 (2011), Article ID 781642, 10 pages
Research Article

Parallel Evolution and Horizontal Gene Transfer of the pst Operon in Firmicutes from Oligotrophic Environments

1Departamento de Ecologia Evolutiva, Instituto de Ecologia, Universidad Nacional Autónoma de México, Apdo. Postal 70-275, Ciudad Universitaria, 04510 México D. F., Mexico
2Departamento de Ingeniería Genética, CINVESTAV Campus Guanajuato, Apdo. Postal 629, 36500 Irapuato, Mexico
3Departamento de Bioquimica, Facultad de Quimica, Universidad Nacional Autonoma de México, Apdo. Postal 70-275, Ciudad Universitaria, 04510 México D. F., Mexico

Received 22 October 2010; Accepted 22 December 2010

Academic Editor: Hiromi Nishida

Copyright © 2011 Alejandra Moreno-Letelier et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The high affinity phosphate transport system (pst) is crucial for phosphate uptake in oligotrophic environments. Cuatro Cienegas Basin (CCB) has extremely low P levels and its endemic Bacillus are closely related to oligotrophic marine Firmicutes. Thus, we expected the pst operon of CCB to share the same evolutionary history and protein similarity to marine Firmicutes. Orthologs of the pst operon were searched in 55 genomes of Firmicutes and 13 outgroups. Phylogenetic reconstructions were performed for the pst operon and 14 concatenated housekeeping genes using maximum likelihood methods. Conserved domains and 3D structures of the phosphate-binding protein (PstS) were also analyzed. The pst operon of Firmicutes shows two highly divergent clades with no correlation to the type of habitat nor a phylogenetic congruence, suggesting horizontal gene transfer. Despite sequence divergence, the PstS protein had a similar 3D structure, which could be due to parallel evolution after horizontal gene transfer events.