The statement of the Dutch microbiologist Bass-Becking‘everything is everywhere, but the environment selects’ (1934) is frequently used as the starting point of many studies on prokaryotic and protist biodiversity and biogeography (de Wit & Bouvier, 2006). ‘Everything is everywhere’ reflects the concept that all microorganisms are cosmopolitan and statement ‘the environment selects’ implies that specific microorganisms are observed in their characteristic environments. The statement of Bass-Becking is now under critical review.
Recent evidence indicates the presence of possible endemism in prokaryotes. Evidence for endemism is largely restricted to samples from extreme environments, for example Synechococcus inhabiting mats in hot springs (Papke et al., 2003) and in Sulfolobus solfataricus (Whitaker et al., 2003).
The literature includes considerable support for the cosmopolitan distribution of prokaryotes, due to their high dispersion capacity, the enormous size of microbial populations and the low probability of extinction (Fenchel, 2003). However, estimates of the scope for their distribution are influenced by the level of taxonomic resolution applied and the technique used to identify them. For example, it is well accepted that Bacteria and Archaea are globally distributed (using 16S rRNA gene sequences) (DeLong & Pace, 2001) but at lower taxonomic levels (e.g. genus level) prokaryotes have a cosmopolitan distribution in their respective habitats (Ramette & Tiedje, 2006).
Although evidence for potential endemism among Cyanobacteria is growing, based on morphological studies, endemism of Cyanobacteria in Antarctic habitats was discarded and Cyanobacteria was considered as having cosmopolitan distribution (Vincent, 2000; Taton et al., 2003). Conversely, molecular tools have revealed evidence for a bipolar distribution of Antarctic and Arctic Cyanobacteria (Comte et al., 2007), and the existence of some clusters that appear endemic for Antarctica (e.g. Taton et al., 2006a; Laybourn-Parry & Pearce, 2007).
In terms of their morphology and phylogenetics, Cyanobacteria are one of the most diverse groups of prokaryotes (Waterbury, 2006). Their ecological tolerance (e.g. to a broad range of temperatures, high salinities, adaptations to light) contributes to their competitive success in a variety of environments, both as planktonic or benthic organisms (Badger et al., 2006; Cohen & Gurevitz, 2006). Cyanobacteria can dominate primary production in some environments including microbial mats (Stal, 1995) and some extreme environments, such as Antarctic permafrost aquatic systems (Jungblut et al., 2005).
Cyanobacteria are currently placed into five orders: Chroococcales, Pleurocapsales, Oscillatoriales, Nostocales and Stigonematales (e.g. Tomitani et al., 2006). Members of the Chroococcales and Oscillatoriales are dispersed throughout the phylogenetic tree, indicating that these two orders at least do not represent coherent evolutionary lineages (Waterbury, 2006). Recent studies in wetlands located in the Chilean Altiplano described high microbial diversity and high spatial variability of the microbial communities (Demergasso et al., 2004). The athalassohaline water bodies located in this area are subject to extreme conditions including high UV radiation, low temperatures, negative water balance and variable salt concentration. Little information is available on cyanobacterial diversity in Andean salares, with the exception of a study examining the microbial mats of the Salar de Llamará, located in the Atacama Desert (Demergasso et al., 2003). This study revealed the presence of Cyanothece sp., Synechococcus sp., Microcoleus sp., Oscillatoria sp., Gloeocapsa sp. and Gloeobacter sp. in different mats. Oscillatoria sp. was also revealed to be a dominant component of the cyanobacterial community of the Laguna Tebenquinche in the Salar de Atacama (Zúñiga et al., 1991). In the same region, Cyanobacteria have been studied in the high altitude El Tatio hot-springs where Chroococcidiopsis sp., Phormidium sp. and Lyngbya sp. were reported (Fernandez-Turiel et al., 2005; Phoenix et al., 2006). Also, studies of quartz stones from the Atacama Desert showed a predominance of hypolithic Cyanobacteria (Warren-Rhodes et al., 2006) and endolithic Cyanobacteria in soil gypsum (Dong et al., 2007).
The Salar de Huasco is an Andean salar (Chong, 1984) located at 3800 m altitude and was selected as a model of altiplanic wetlands because it is subject to low anthropogenic perturbations and exhibits visual spatial variability. Using 16S rRNA gene clone libraries and PCR-denaturing gradient gel electrophoresis (DGGE), we examined cyanobacterial community structure in water and sediment samples collected from four different sites within the Salar de Huasco. We also discussed the biogeographical relationships of Cyanobacteria found in this almost unexplored habitat and possible connections to other extreme habitats.