The biodiversity of cyanobacteria in Antarctic microbial mats
Wilmotte A1, Fernandez-Carazo R1, Zakhia F1, Simon P1, Taton A1, Hodgson DA2 ,Verleyen E3
1 Centre d’ingénierie des protéines, Institut de Chimie B6, Université de Liège, B-4000 Liège, Belgique 2 British Antarctic Survey, High Cross, Madingley Road, Cambridge, UK
3. Ghent University, Protistology and Aquatic Ecology, Krijgslaan 281 S8, B-9000 Gent, Belgium
The biodiversity and distribution of cyanobacteria from microbial mat samples of Antarctic lakes and meltwaters was studied in 4 different regions: Eastern Antarctica, McMurdo Dry Valleys, Antarctic Peninsula and Transantarctic Mountains. The survey was carried out with clone libraries and Denaturating Gradient Gel Electrophoresis based on rRNA sequences (16S rRNA and the Internal Transcribed Spacer). Moreover, 60 strains were isolated and genotypically characterised. For the analysis, OTUs (Operational
Taxonomic Units) were defined as groups of 16S rRNA sequences sharing more than 97.5% similarity.
A total of 65 OTUs were identified among our sequences, of which a majority has not been recorded for non-Antarctic sites (absent from databases). This suggests a high degree of endemism.
The four samples from the most hostile biotopes (Transantarctic Mountains) had a particularly poor diversity (from 2 to 5 OTUs). This is in contrast with the higher diversity found in the other regions, varying from 4 to 12 OTUs. Multivariate analyses have shown that salinity and depth (correlated to light) were important factors to explain the distribution of cyanobacterial OTUs. In almost each sample studied, new OTUs were found. Thus, the bulk of the cyanobacterial genomic diversity in Antarctic biotopes still remains to be discovered.
