| Summary: | Experiments with microbial biofilms in microgravity and simulated microgravity have revealed altered growth kinetics, but geomicrobial biofilms have not yet been studied in low gravity environments. No characterisation of biofilms, geomicrobial or otherwise, have been conducted at hypergravity. This thesis explores factors affecting microbe-mineral interactions under terrestrial conditions, lays the groundwork for a scheduled microgravity experiment, and provides the first data on biofilms grown at hypergravity. As a first step in understanding microbe-mineral interactions in altered gravity environments, experiments were undertaken to identify factors that constrain attachment in a terrestrial environment. The model organism Sphingomonas desiccabilis and basaltic rock from Iceland were selected, and the minerals that make up the basalt were identified and procured in their pure form. The relative significance of physical factors such as hydrophobicity, surface charge, porosity and nutritional value were examined in relationship to the success with which biofilms colonised the mineral surfaces. Growth was measured by the quantity of biofilm biomass after a ifxed time period, using Crystal Violet stain, in order to draw conclusions about the most influential physical conditions on biofilm attachment to a substrate. It was found that mineral attachment is influenced more by porosity and nutritional value than by hydrophobicity or surface charge. To explore how reduced gravity affects biofilm formation and weathering rates, a European Space Agency experiment, BioRock, is underway. Samples of basalt, with monocultures of three different organisms, will be sent to the International Space Station in 2019 for long-term exposure to Martian and micro-gravity. Research testing proof of concepts, material compatibility, and experimental procedure and equipment is described. Confocal laser scanning microscopy (CLSM) was used to image the biofilms, and inductively coupled plasma mass spectroscopy (ICP-MS) experiments were ...
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