Author

Natalie Tyler

Date of Award

Spring 2019

Document Type

Open Access Thesis

Department

Earth and Ocean Sciences

First Advisor

Lori Ziolkowski

Abstract

Microbes adapt to inhospitable conditions by colonizing niches that protect them from severe environmental conditions, making them model organisms in the search for life on other planets. Endoliths are globally ubiquitous microbes that colonize structural cavities within rocks, which protect them from environmental stressors while maintaining access to nutrition and light sources. Despite harsh katabatic winds, extreme temperature fluctuations, harmful UV radiation and exposure to desiccation, endolithic communities have been observed in Antarctica. Previous studies have found viable and abundant microbial biomass through microscopy and the addition of isotopic labels. However, due to the slow metabolic activity of these microbes, very little is known about the in-situ activities of these communities – especially in regions outside the McMurdo Dry Valleys where endoliths are thought to be cycling carbon on centennial to millennial time scales. Here we show that East Antarctic endoliths are cycling carbon quickly and are therefore quite active. Through radiocarbon (14C) analyses of the viable cell membrane (as PLFA), we found that the D14C composition of these microbial communities were on average predominantly modern, with a few samples signaling older carbon in the system. These findings indicate that Antarctic endoliths are cycling carbon on decadal time scales rather than on a centennial or millennial scale. This work provides new insights into the potential variability of Antarctic endolith activities and demonstrates that, despite the climatic extremes that exist farther inland on the most inhospitable continent on Earth, indigenous life can thrive.

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Geology Commons

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