| Summary: | Background: Cystic fibrosis is the most common inheritable genetic disease affecting 1 in 2500 new born Caucasian infants. The primary cause of morbidity and mortality in these individuals is respiratory failure resulting from chronic airway infections. Previous studies have shown that many bacterial species colonise the airways at any one time. These results have suggested the need for understanding the ecological mechanisms occurring within these communities. This thesis uses ecological experiments to assess the impact of biodiversity on the activity of bacterial assemblages. Methods: Bacterial species and P. aeruginosa ecotypes, isolated from expectorated sputum samples and identified using 16S rRNA gene sequence variation, were assembled into combinations of increasing diversity. These assemblages were inoculated into different environments to assess their effect on respiration. Total respiration was monitored using the MicroResp™ or the BIOLOG EcoPlate™ systems. A general linear model approach was used to analyse the data and investigate the ability of three ecological processes (species richness, composition and interactions) to account for the observed variance. Results: Richness was generally shown to be statistically significant in all environments tested with mixed species present (p < 0.005). Conversely, when P. aeruginosa ecotypes were present no effect of richness was observed (p > 0.272). Composition was found to account for significant variation in the data in all environments and species combinations (p < 0.001). Altering the environment was shown to affect the significance of productivity and interactions among the species. Conclusions: The experiments reported within show a novel application of established ecological models. These identify a complex interplay of mechanisms within the bacterial assemblages that are dependent on the environment and relatedness of the bacteria present.
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