Diversity and distribution of microorganisms in microbial mats of Antarctic lakes

The BelSPO project CCAMBIO aims to study the biogeographical distribution of microorganisms in lacustrine microbial mats using a combination of techniques including microscopic observations, strain isolation and genetic characterisation, and molecular diversity assessments using Next Generation Sequencing of environmental DNA. The samples were collected in different Antarctic and sub-Antarctic biogeographical regions.
Preliminary multivariate analysis of >130 samples revealed strong bioregionalisation patterns in microbial eukaryotes, which are in agreement with the classical subdivision of the Antarctic Realm into Maritime Antarctica, Continental Antarctica and the Sub-Antarctic Islands generally observed in plants and animals. The biogeographic structuring was less strong between the continent and Maritime Antarctica in prokaryotes suggesting more regular dispersal events between these two regions. The Sub-Antarctic assemblages harboured more complex foodwebs, with arthropods, nematods, rotifers, flatworms and annelids as main metazoan groups. Lakes on the continent, however, were characterised by fewer metazoan groups and a greater importance of microbial herbivores and secondary consumers, including a relative high diversity of ciliates and tardigrades. In a first analysis of microbial mats from five Antarctic lakes and an aquatic biofilm from the Sub-Antarctic, the majority of the cyanobacterial OTUs retrieved were related to filamentous taxa such as Leptolyngbya and Phormidium, which are common genera in Antarctic lacustrine microbial mats. However, other phylotypes related to different taxa such as Geitlerinema, Pseudanabaena, Synechococcus, Chamaesiphon, Calothrix and Coleodesmium were also found. Results revealed a much higher diversity than what had been reported using traditional methods and also highlighted remarkable differences between the cyanobacterial communities of the studied lakes. In the coming months, the molecular diversity data will be deposited into the “Microbial Antarctic Resource System (MARS)” presently developed into the webportal ‘biodiversity.aq’. Better knowledge of the diversity and distribution of microorganisms will contribute to a better assessment of their resilience and local/regional responses to global change