An endangered oasis of aquatic microbial biodiversity in the Chihuahuan desert

doi:10.1073/pnas.0601434103

An endangered oasis of aquatic microbial biodiversity in the Chihuahuan desert

*Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México AP 70-275 Coyoacán, 04510 Mexico D.F., Mexico;
^‡Department of Geological Sciences, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404;
^§Department of Biological Sciences, University of Idaho, Moscow, ID 83844;
^¶Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México AP 510-3 Cuernavaca, Morelos, 62271, Mexico;
**Departamento de Geohidrología y Geofísica, Instituto de Ingeniería Civil, Universidad Autónoma de Nuevo León Avenida Fidel Velásquez y Universidad CD Universitaria, 66451 San Nicolás de los Garza N.L., Mexico; and
^††School of Life Sciences, Arizona State University, Tempe, AZ 85287

Communicated by José Sarukhán, National Autonomous University of Mexico, Mexico D.F., Mexico, February 23, 2006 (received for review September 1, 2005)

Abstract

The Cuatro Cienegas basin in the Chihuahuan desert is a system of springs, streams, and pools. These ecosystems support >70 endemic species and abundant living stromatolites and other microbial communities, representing a desert oasis of high biodiversity. Here, we combine data from molecular microbiology and geology to document the microbial biodiversity of this unique environment. Ten water samples from locations within the Cuatro Cienegas basin and two neighboring valleys as well as three samples of wet sediments were analyzed. The phylogeny of prokaryotic populations in the samples was determined by characterizing cultured organisms and by PCR amplification and sequencing of 16S rRNA genes from total community DNA. The composition of microbial communities was also assessed by determining profiles of terminal restriction site polymorphisms of 16S rRNA genes in total community DNA. There were 250 different phylotypes among the 350 cultivated strains. Ninety-eight partial 16S rRNA gene sequences were obtained and classified. The clones represented 38 unique phylotypes from ten major lineages of Bacteria and one of Archaea. Unexpectedly, 50% of the phylotypes were most closely related to marine taxa, even though these environments have not been in contact with the ocean for tens of millions of years. Furthermore, terminal restriction site polymorphism profiles and geological data suggest that the aquatic ecosystems of Cuatro Cienegas are hydrologically interconnected with adjacent valleys recently targeted for agricultural intensification. The findings underscore the conservation value of desert aquatic ecosystems and the urgent need for study and preservation of freshwater microbial communities.

Footnotes

^†To whom correspondence should be addressed. E-mail: souza{at}servidor.unam.mx
↵ ^‖Present address: Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico.
Author contributions: V.S., L.E.E., and J.J.E. designed research; V.S., L.E.-A., A.E.E., J.F., L.F., L.L., L.E.E., and J.M.R.-M. performed research; V.S., L.E.E., J.F., L.F., X.S., and J.J.E. contributed new reagents/analytic tools; V.S., L.E.-A., A.E.E., J.F., L.F., X.S., and R.D. analyzed data; and V.S., L.E.-A., A.E.E., L.E.E., J.F., L.F., R.D., and J.J.E. wrote the paper.
Conflict of interest statement: No conflicts declared.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AY604936–AY604973).
Abbreviations:

Abbreviations:

CCB,

Cuatro Cienegas basin;

T-RFLP,

terminal restriction site polymorphism.