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Microbial Dynamics and Plant-Microbe Interactions in a Hypobaric Higher-Plant Chamber: Implications for Advanced Life Support in Space

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Title: Microbial Dynamics and Plant-Microbe Interactions in a Hypobaric Higher-Plant Chamber: Implications for Advanced Life Support in Space
Author: MacIntyre, Olathe Jean
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Dixon, Michael
Abstract: This study examines the effects of hypobaria and hypoxia on microbial communities in a higher-plant chamber (HPC), plant-microbe interactions, and plant productivity. A HPC for advanced life support (ALS) on the Moon or Mars will likely have a hypobaric (low pressure) atmosphere relative to Earth. It is generally accepted that microbial control in a HPC in space will be accomplished through good sanitation practices and the establishment of an engineered microbial community. To achieve a level of microbial diversity that would confer protection from microbial contamination, a stable microbial community with beneficial microbes could be established in an analogue HPC. This analogue HPC may need to have the same atmospheric conditions as the HPC in space. Three experiments were conducted with the objective of testing for effects of hypobaria and altered atmospheric compositions on plant productivity, bacterial communities, and plant-microbe interactions in a HPC. Reduced pressure down to 10 kPa and reduced partial pressure of oxygen (pO2) down to 2 kPa had little to no effect on abundance of culturable bacteria. However, community-level physiological profiles of bacterial communities in the nutrient solutions of radish and soybean were affected by altered atmospheric conditions. Inoculation of radish with Bacillus subtilis reduced edible dry mass production by 22 % under ambient and hypoxic conditions of 7 kPa pO2. Bradyrhizobium japonicum was able to form nodules and fix nitrogen with soybeans at 25 kPa total pressure with 19 kPa partial pressure of nitrogen (pN2) and 5 kPa pO2. A lower pN2 may be adequate for N2 fixation, but at 5 kPa pO2 reproductive growth was inhibited relative to ambient conditions. These findings suggest that a bacterial community can be maintained and plant-microbe interactions can be effective with altered atmospheric conditions suitable for supporting hypobaric plant-growth. However, altered atmospheric conditions change the microbial dynamics of a community and beneficial bacteria that are maintaining an effective population under ambient conditions may be out-competed under altered atmospheric conditions. Therefore it is recommended that the atmospheric conditions anticipated for a HPC on the Moon or Mars be used in the analogue HPC for tests of plant-microbe interactions and for engineering a stable microbial community to be used in space.
URI: http://hdl.handle.net/10214/7766
Date: 2013-12
Rights: Attribution-NoDerivs 2.5 Canada


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Attribution-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NoDerivs 2.5 Canada