1639-1Unexpected abundance of specific archeal and eubacterial OTUs in low impacted ice-free soil at King George Island, Antarctic Peninsula
Autores:Cesar Osorio-forero (CORPOGEN - CorpoGen) ; Igor Stelmach Pessi (UFRGS - Universidade Federal do Rio Grande do Sul) ; Howard Junca (CORPOGEN - CorpoGen) ; Felipe L. Simoes (UFRGS - Universidade Federal do Rio Grande do Sul) ; Jefferson C. Simoes (UFRGS - Universidade Federal do Rio Grande do Sul) ; Alexandre José Macedo (UFRGS - Universidade Federal do Rio Grande do Sul)


Antarctica, the colder and dryer environment on Earth, harbors a unique diversity of microorganisms which have evolved for millions of years under harsh conditions. Antarctic Peninsula is located at a global intersection of environmental conditions, being the physical barrier to tropospheric circulation, in a cross-like interphase of contrasting climates such as coastal maritime west, continental east coast, warmer north and colder polar south, constituting a unique harsh and shifting environment. Although a number of studies have showed that microbial communities thriving in relatively stable Antarctic environments are diverse, it is likely that due to methodological issues the precise assessment of microbial diversity has been largely underestimated. In this study we analyze, by means of 16S pyrotags, more than 49,000 sequences to study the taxonomical composition and microbial diversity of soil microbial communities at four neighboring subsampling points representing the coastal shoreline soil of an undisturbed ice-free cove at King George Island, Antarctic Peninsula. Overall the taxonomic classification of the sequences revealed that the communities are composed of 17 highly divergent phyla, with a predominance of Proteobacteria, Bacteroidetes and Euryarchaeota. An important fraction of the communities studied consistently retrieved a unique abundant OTU0.03 belonging to Euryarchaeota phylum across all the localities sampled. Regarding sequence distribution and frequency in OTU accumulation, the results indicated that these communities follow the pattern coined as “rare biosphere”, with some OTUs defined by just one divergent single sequence, indicating the presence of very different phylogenetic groups in very low abundance. Altogether, these findings suggest that Antarctic microbial communities in this area are highly diverse and composed of many unknown microbial species, some of them with a high relative abundance, indicating that it is an ecosystem harboring specific and unique predominant types probably endemically selected, representing a vast metagenomic potential of unexplored functional capabilities hosted in this extreme environment.

Palavras-chave:  Microbial diversity, Antarctic, Metagenomics, Archeal, Eubacterial