Phylogenetic analysis of bacterial populations in waters of the former Texcoco Lake, Mexico.

Molecular techniques were used to compare the compositions of the bacterial communities of the 2 following lagoons from the former soda Texcoco Lake, Mexico: the restored Facultativa lagoon and the Nabor Carrillo lagoon. Ribosomal intergenic spacer analysis (RISA) revealed that bacterial communities of the 2 lagoons were different and presented a relatively low diversity. Clone libraries of 16S rDNA genes were constructed, and significant phylotypes were distinguished by restriction fragment length polymorphism (RFLP). A representative clone from each phylotype was partially sequenced. Molecular identification and phylogenetic analyses based on ribosomal sequences revealed that the Facultativa lagoon harbored mainly gamma- and beta-Proteobacteria, low G+C Gram-positive bacteria, and several members of the Halobacteriaceae family of archaea. The Nabor Carrillo lagoon mainly included typical halophilic and alkaliphilic low G+C Gram-positive bacteria, gamma-Proteobacteria, and beta-Proteobacteria similar to those found in other soda lakes. Several probably noncultured new bacterial species were detected. Three strains were isolated from the Nabor Carrillo lagoon, their partial 16S rDNA sequences were obtained. On this basis, they were identified as Halomonas magadiensis (H1), Halomonas eurihalina (H2), and Staphylococcus sciuri (H3). This is the first study that uses molecular techniques to investigate potential genetic diversity in the Texcoco lakes. In this preliminary evaluation, we infer the presence of alkalophilic, halophilic, or haloalkaliphilic bacteria potentially useful for biotechnology.