The spatial structures of hypolithic communities in the Dry Valleys of East Antarctica
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Hypolithic communities represent important reservoirs of microbial life in hyper-arid deserts. A number of studies on the diversity and ecology of these communities from different geographic areas have been reported in the past decade, but the spatial distribution of the different components of these communities is still not understood. Moss- and cyanobacteria-dominated hypolithic community morphotypes from Miers Valley (McMurdo Dry Valleys, East Antarctica) were analyzed by electron microscopy in order to characterize the microscale spatial structure. The two communities showed a high degree of internal organization, but differing according to the biological composition. In moss-dominated hypoliths, the moss plantlets are intermixed with mineral fragments of soil origin. However, in cyanobacteria-dominated hypoliths, a layered spatial organization was structured by filamentous cyanobacteria and associated extracellular polymeric components. While moss cells were lacking in cyanobacteria-dominated communities, biofilms formed by cyanobacteria and heterotrophic bacteria were observed in both community morphotypes. The water-holding capacity of both live and dead moss cells and the associated organic matrix, together with the protective properties of the extracellular polymeric substances, could facilitate the survival and activity of these communities. Similar structural strategies can favor the survival of microbial communities in different extreme environments.
KeywordsAntarctica Biofilm Cyanobacteria EPS Hypoliths Moss
We are grateful to Antarctica New Zealand (AntNZ) for logistical support. The New Zealand Foundation for Research, Science and Technology (FRST), the University of Waikato Vice Chancellor’s Fund, and the Department of Biological Sciences, University of Waikato provided financial support to SCC. DAC acknowledges financial support from the South African NRF SANAP program and the UP Genomics Research Institute. The microscopy study was funded by the Spanish Education Ministry grant CTM2012-38222-C02-02. The authors would like to thank to the ICA and the MNCN microscopy services staff for technical assistance and Glen Stichbury (University of Waikato) for elaborating the maps.
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