ORIGINAL PAPER Novelty and spatio–temporal heterogeneity in the bacterial diversity of hypersaline Lake Tebenquiche (Salar de Atacama) Cecilia Demergasso Æ Lorena Escudero Æ Emilio O. Casamayor Æ Guillermo Chong Æ Vanessa Balague ´ Æ Carlos Pedro ´s-Alio ´ Received: 27 December 2007 / Accepted: 13 February 2008 / Published online: 18 March 2008 Ó Springer 2008 Abstract Lake Tebenquiche is one of the largest saline water bodies in the Salar de Atacama at 2,500 m above sea level in northeastern Chile. Bacteria inhabiting there have to deal with extreme changes in salinity, temperature and UV dose (i.e., high environmental dissimilarity in the physical landscape). We analyzed the bacterioplankton structure of this lake by 16S rRNA gene analyses along a spatio–temporal survey. The bacterial assemblage within the lake was quite heterogeneous both in space and time. Salinity changed both in space and time ranging between 1 and 30% (w/v), and total abundances of planktonic pro- karyotes in the different sampling points within the lake ranged between two and nine times 10 6 cells mL -1 . Community composition changed accordingly to the par- ticular salinity of each point as depicted by genetic fingerprinting analyses (denaturing gradient gel electro- phoresis), showing a high level of variation in species composition from place to place (beta-diversity). Three selected sites were analyzed in more detail by clone libraries. We observed a predominance of Bacteroidetes (about one third of the clones) and Gammaproteobacteria (another third) with respect to all the other bacterial groups. The diversity of Bacteroidetes sequences was large and showed a remarkable degree of novelty. Bacteroidetes formed at least four clusters with no cultured relatives in databases and rather distantly related to any known 16S rRNA sequence. Within this phylum, a rich and diverse presence of Salinibacter relatives was found in the saltiest part of the lake. Lake Tebenquiche included several novel microorganisms of environmental importance and appeared as a large unexplored reservoir of unknown bacteria. Keywords 16S rRNA gene Á Bacteroidetes Á Biodiversity Á Clone libraries Á DGGE Á Ecology Á Extremophiles Á Fingerprinting Á Gammaproteobacteria Á Hypersaline Á Salar Á Salt lake Á Tebenquiche Introduction Diversity of microbial communities is believed to be very large and poorly characterized (see overview in Pedro ´s- Alio ´ 2006). Yet, its knowledge is of interest for several reasons, both practical and theoretical. Bacterial diversity is a reservoir of potentially interesting genes for biotech- nology and medicine, and the large seed-bank of bacterial taxa hidden in natural communities should be of interest to better delineate both the taxonomy and the evolutionary Communicated by K. Horikoshi. C. Demergasso Centro de Biotecnologı ´a, Universidad Cato ´lica del Norte, Avda. Angamos 0610, Antofagasta, Chile C. Demergasso Á L. Escudero Á G. Chong Centro de Investigacio ´n Cientı ´fica y Tecnolo ´gica para la Minerı ´a, Regio ´n de Antofagasta, Chile E. O. Casamayor (&) Unitat de Limnologia, Centre d’Estudis Avanc ¸ats de Blanes (CSIC), Acce ´s Cala Sant Francesc-14, E17300 Blanes, Spain e-mail: casamayor@ceab.csic.es G. Chong Departamento de Ciencias Geolo ´gicas, Universidad Cato ´lica del Norte, Avda. Angamos 0610, Antofagasta, Chile L. Escudero Á V. Balague ´ Á C. Pedro ´s-Alio ´ Departament de Biologia Marina i Oceanografia, Institut de Cie `ncies del Mar, CSIC, Passeig Marı ´tim de la Barceloneta 37-49, 08003 Barcelona, Spain 123 Extremophiles (2008) 12:491–504 DOI 10.1007/s00792-008-0153-y