Microbial diversity of Antarctic lakes: a polyphasic approach combining from microscopy to molecular biology

IZAGUIRRE, I.; UNREIN, F.; MASSANA, R.; BALAGUÉ, V.; GASOL, J. M.

St. John’s, Newoundland (Canada)

Congreso; ASLO Summer Meeting 2008; 2008

ASLO

The microbial diversity in lakes of Hope Bay (Antarctic Peninsula) has been studied during the last 15 years. The first diversity studies of the plankton communities of these lakes involved traditional examinations of living and fixed (?) specimens by microscopy, and taxonomical identifications using published literature. These studies allowed identifying mostly microplanktonic species (> 20 µm), among which some belonged to the algal mats (diatoms, filamentous Cyanobacteria). The biodiversity of small flagellates (3 – 20 µm), one of the main components of the microbial plankton in these lakes, and pico-eukaryotes, remained relatively uncertain until the use of molecular techniques. A molecular fingerprinting analysis (DGGE) revealed the presence of five different Chrysophyceae, including uniflagellated and biflagellated organisms. Latter on, clone libraries were performed with samples of two type-lakes of this region, obtaining the sequences of the main nanoplankton species: several Chrysophyceae (among them an Ochromonas species), and Chlorophyceae (including five Chlamydomonas species). Some of these sequences showed high similarities with sequences found in other Antarctic regions. Finally, the combined use of epifluorescence microscopy, flow cytometry and FISH allowed the quantification and differentiation of picoeukaryotic populations.