Microbial stress in rock habitats
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Date
26/11/2015Author
Bryce, Casey Catherine
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Abstract
Micro-organisms are the most abundant and diverse form of life on Earth.
Their ability to tolerate stress has enabled them to colonise many inhospitable
environments. Microbial processes alter the chemistry of the environment which
has left a lasting mark on the geological record. On the other hand, microbial
life is heavily influenced by environmental conditions. Indeed, the history of the
Earth is shaped by the co-evolution of microbial and geological processes.
This thesis explores how micro-organisms are influenced by their environment,
with particular reference to microbial rock habitats. Rock habitats are an
interesting system to understand the inter-relationship between microbial life and
it's environment as they are relatively simple and very common. Rock-dwelling
communities are also exposed to numerous stresses such as surface UV exposure,
desiccation, temperature fluctuations, low nutrient availability or toxicity from
elements leached from the rocks themselves. Three specific aspects of microbial
stress in rock environments are investigated here: 1) The use of rocks as a shield
from surface UV radiation stress, 2) The microbial response to chemical changes
during water-rock interactions, 3) The effect of simultaneous limitation of more
than one nutrient.
The first uses exposure facilities aboard the International Space Station to provide
empirical evidence that colonisation of the early land masses by phototrophs was
not inhibited by high surface UV radiation. The latter studies use quantitative
proteomics to investigate the cellular response of a heterotrophic bacterium to
nutrient deficiency and element leaching, two common stresses in rock habitats.
Together these results further our understanding of the relationship between
micro-organisms and rocks, both today and over geological time.
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