Characterization of cyanobacterial communities from high-elevation lakes in the Bolivian Andes

The Bolivian Altiplano is a harsh environment for life with high solar irradiation (visible and UVR), below freezing temperatures, and some of the lowest precipitation rates on the planet. However, microbial life is visibly abundant in small isolated refugia of spring or snowmelt-fed lakes. In this study, we characterized the cyanobacterial composition of a variety of microbial mats present in three lake systems: Laguna Blanca, Laguna Verde (elevation 4300 m), and a summit lake in the Licancabur Volcano cone (elevation 5970 m). These lakes and their adjacent geothermal springs present an interesting diversity of environments within a geographically small region (5 km(2)). From these sites, 78 cyanobacterial cultures were isolated in addition to similar to 400 cyanobacterial 16S rRNA gene sequences from environmental genomic DNA. Based on microscopy, cultivation, and molecular analyses, these communities contained many heterocytous, nitrogen-fixing cyanobacteria (e.g., Calothrix, Nostoc, Nodularia) as well as a large number of cyanobacteria belonging to the form-genus Leptolyngbya. More than a third (37%) of all taxa in this study were new species (<= 96% 16S rRNA gene sequence identity), and 11% represented new and novel taxa distantly related (<= 93% identity) to any known cyanobacteria. This is one of the few studies to characterize cyanobacterial communities based on both cultivation-dependent and cultivation-independent analyses.