Bacteria in Extreme Environments: A Study of how Physiology, Gene Content, and Community Structure are Influenced by Abiotic Factors

ISBN-10
1124479899
ISBN-13
9781124479897
Category
Bacteria
Language
English
Published
2011
Author
Julie L. Smith

Description

Our survival on this planet is dependent upon the microbial life which surrounds us. Microorganisms occupy every niche possible, including not only the small fraction of the biosphere deemed habitable by humans, but also the bulk of the biosphere which exhibits conditions we consider extreme. These conditions can constrain the development of complex ecosystems, allowing microorganisms to dominate the landscape. This reduced ecological complexity may allow us to more easily determine the functional roles of individual members of the microbial community. Thus, extreme environments can serve as model systems for more diverse habitats as well as shed light on the limits of life under extreme conditions. This dissertation includes an examination of bacteria from three different extreme environments: deep-sea hydrothermal vents, Antarctic soils, and an Antarctic subglacial lake. At deep-sea hydrothermal vent systems hot, anoxic, metal-rich vent effluents mix with cold oxygenated seawater, providing a gradient of redox conditions and highly variable environmental parameters across short distances. Organisms in this habitat are exposed to high temperatures, high pressure, heavy metals, and rapidly fluctuating conditions. Here, a member of the vent community, Nautilia profundicola, is characterized by its physiological capabilities as well as by its gene content, both of which show adaptations to the highly dynamic hydrothermal vent environment. Microorganisms inhabiting Antarctic soils are faced with nearly constant freezing temperatures, months of darkness and soils that are highly saline, nutrient-limited and incredibly arid. Here, soils from a latitudinal gradient in Antarctica were examined to determine how bacterial community structure was affected by soil physicochemical properties. In these Antarctic soils, microbial diversity and community structure were driven by environmental parameters such as soil moisture and pH. For Antarctic glacial and subglacial ice, a set of strict protocols and authenticity criteria were developed and implemented to study microbial assemblages which may yield valuable information about how microorganisms survive in ancient subglacial lakes. Each of these extreme environments harbors microbial communities which face strong selective pressures. Both culture-dependent and culture-independent methods were used to examine microbial assemblages found in these extreme environments to reveal how bacteria survive and thrive in extreme environments.

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