College of Agriculture

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Life in High-Temperature Environments: Modern-Day Analogs of Early Earth Still Relevant Today
(2017-09) Inskeep, William P.
The discovery of new single-celled organism lineages has been remarkable since the adoption of molecular genetics and the discovery of the domain Archaea (Woese et al., 1990). Prior to molecular techniques that initially emphasized the sequences of ribosomal genes (e.g., 16S rRNA), the discipline of microbiology relied nearly entirely on cultivation and the ability to grow a specific microorganism in pure culture under defined conditions. This meant that only microorganisms that grew easily under laboratory conditions were cultivated, and, in many cases, these often rapidly growing organisms do not correspond to the more numerous and relevant microbes that actually inhabit different microbiomes. We now appreciate that many of the microorganisms easily grown under laboratory conditions are often related to their more abundant and important relatives found in situ, but they generally do not exhibit the same functional attributes as numerically relevant microorganisms.
Lakes of Antarctica
(2009) Priscu, John C.; Foreman, Christine M.
Introduction:The evolutionary history of Antarctic lakes reflects the history of the continent itself. More than 170 Mya, Antarctica was part of the supercontinent Gondwana. Over time Gondwana broke apart and Antarctica, as we know it today, was formed around 25 Mya. During its evolution, the continent underwent numerous climate shifts. Around 65 Mya, Antarctica still had a tropical to subtropical climate, complete with an Australasian flora and fauna. Ice first began to appear around 40 Mya. The opening of the Drake Passage between Antarctica and South America around 23 Mya resulted in the Antarctic Circumpolar Current, which effectively isolated the advection of lower latitude warm water to the region, leading to continent-scale glaciations that now typify Antarctica. The period between 14.8 and 13.6 Mya (mid Miocene) saw an important change in the landscape evolution. During this time, the linked climate and-glacial system changed from one dominated by intermittent fluvial erosion and wet-based glaciation, to one featuring a largely cold-based ice sheet, with cold-based alpine glaciers in the hyperarid, cold desert conditions of the Transantarctic Mountains. The last Antarctic glaciation reached a maximum around 18 000 years ago, a period when the present ice sheet was much thicker and extended out to the edge of the continental shelf. The icecaps of offshore islands were similarly more extensive. These extensive ice sheets retreated during the late Pleistocene and have remained relatively stable during the current Holocene epoch. As a result of this temporal evolution, we now see lakes distributed on maritime islands, along the margins of the continent in ablation regions, and subglacially, beneath the thick ice sheet. All these lakes reflect, to varying degrees, the legacy left by past geological and climatological conditions. This article describes the formation, distribution, and diversity of lakes in selected regions in Antarctica where focused research efforts have occurred. Although no subglacial lakes have been sampled directly, we present an overview of what is known about them,with a focus on Lake Vostok, the largest of these lakes.
Bacteria in subglacial environments
(2008) Christner, Brent C.; Skidmore, Mark L.; Priscu, John C.; Tranter, Martyn; Foreman, Christine M.
Glaciers exist where the annual temperature remains cold enough to allow snowfall to accumulate for an extended period of time and where conditions allow subsequent metamorphosis to ice. Glacial ice forms expansive continental ice sheets in the polar regions, (e.g., in Antarctica and Greenland), and at lower latitudes, ice fields (valley or alpine glaciers) and ice caps (if a volcano or mountain range is completely glaciated) exist globally at high altitude. Temperate glaciers comprise <4% of the glacial ice on the planet, but are important freshwater reservoirs and are often the sources for major rivers vital for irrigation, industry, and providing millions of people with drinking water. The Greenland and Antarctic ice sheets currently cover ~10% of the terrestrial surface (>1.5Ã—107 km2) and contain ~75% of the freshwater on Earth (Paterson 1994). The Antarctic ice sheet alone contains ~90% of the planet's ice and, if melted, would result in a sea level rise of ~65 m (The National Snow and Ice Data Center; http://nsidc.org/).

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