Molecular characterization of bacteria from permafrost of the Taylor Valley, Antarctica.

While bacterial communities from McMurdo Dry Valley soils have been studied using molecular techniques, data from permafrost are particularly scarce given the logistical difficulties of sampling. This study examined the molecular diversity and culturability of bacteria in permafrost from the Taylor Valley (TV), Antarctica. A 16S rRNA gene clone library was constructed to assess bacterial diversity, while a clone library of the RNA polymerase beta subunit (rpoB) gene was constructed to examine amino acid composition of an essential protein-coding gene. The 16S rRNA gene clone library was dominated by Acidobacteria from Gp6 and Gemmatimonadetes. The rpoB gene clone library (created with primers designed in this study) was also dominated by Acidobacteria. The ability of sequence analyses to garner additional information about organisms represented by TV sequences was explored. Specifically, optimum growth temperature was estimated from the stem GC content of the 16S rRNA gene, while potential cold adaptations within translated rpoB sequences were assessed. These analyses were benchmarked using known psychrophiles and mesophiles. Bioinformatic analyses suggested that many TV sequences could represent organisms capable of activity at low temperatures. Plate counts confirmed that c. 10(3) cells per gram permafrost remained viable and were culturable, while laboratory respiration assays demonstrated that microbial activity occurred at -5 °C and peaked at 15 °C.

Discovery of natural perchlorate in the Antarctic Dry Valleys and its global implications.

In the past few years, it has become increasingly apparent that perchlorate (ClO(4)(-)) is present on all continents, except the polar regions where it had not yet been assessed, and that it may have a significant natural source. Here, we report on the discovery of perchlorate in soil and ice from several Antarctic Dry Valleys (ADVs) where concentrations reach up to 1100 microg/kg. In the driest ADV, perchlorate correlates with atmospherically deposited nitrate. Far from anthropogenic activity, ADV perchlorate provides unambiguous evidence that natural perchlorate is ubiquitous on Earth. The discovery has significant implications for the origin of perchlorate, its global biogeochemical interactions, and possible interactions with the polar ice sheets. The results support the hypotheses that perchlorate is produced globally and continuously in the Earth's atmosphere, that it typically accumulates in hyperarid areas, and that it does not build up in oceans or other wet environments most likely because of microbial reduction on a global scale.