Arsenic metabolism in high altitude modern stromatolites revealed by metagenomic analysis

KURTH, D; AMADIO, A; ORDOÑEZ, OF; ALBARRACIN, VH; GÄRTNER, W; FARIAS, ME

Scientific Reports

Springer Nature

Lugar: London; Año: 2017 vol. 7

Modern stromatolites thrive only in selected locations in the world.Socompa Lake, located in the Andean plateau at 3570 masl, is one of thenumerous extreme Andean microbial ecosystems described over recentyears. Extreme environmental conditions include hypersalinity, high UVincidence, and high arsenic content, among others. After Socompa?sstromatolite microbial communities were analysed by metagenomic DNAsequencing, taxonomic classification showed dominance of Proteobacteria,Bacteroidetes and Firmicutes, and a remarkably high number of unclassified sequences. A functional analysis indicated that carbon fixation might occur not only by the Calvin-Benson cycle, but also through alternative pathways such as the reverse TCA cycle, and the reductive acetyl-CoA pathway. Deltaproteobacteria were involved both in sulfate reduction and nitrogen fixation. Significant differences were found when comparing the Socompa stromatolite metagenome to the Shark Bay (Australia) smooth mat metagenome: namely, those involving stress related processes, particularly, arsenic resistance. An in-depth analysis revealed a surprisingly diverse metabolism comprising all known types of As resistance and energy generating pathways. While the ars operon was the main mechanism, an important abundance of arsM genes was observed in selected phyla. The data resulting from this work will prove a cornerstone for further studies on this rare microbial community.