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University of New South Wales (UNSW) 2016

Microbial assemblages associated with extreme Australian environments and their biosynthetic potential

Vardeh David Paul

Titre : Microbial assemblages associated with extreme Australian environments and their biosynthetic potential

Auteur : Vardeh David Paul

Université de soutenance : University of New South Wales (UNSW)

Grade : Doctor of Philosophy (PhD) 2016

Résumé
A wealth of unknown microbial clades and metabolic abilities from physically extreme habitats has been uncovered in recent decades, but the underlying parameters that shapemicrobial communities in challenging environments are still poorly understood. Theadaptations of microbes to these stressors are conferred by specialised biosyntheticpathways to protect against desiccation, osmotic stress and high or low solar irradiation.These compounds could harbour pharmaceutically active functions but their discovery, characterisation and subsequent production are hindered by the lack of cultivable representative extremophile strains. This study explores mat and microbialite biofilmcommunities under extreme conditions that have not been described in depth before. Inaddition, their biosynthetic potential is evaluated and the variability within and betweendifferent habitats is explored. Next generation sequencing of the 16S rRNA gene and of two conserved domains of non-ribosomal biosynthetic pathways was performed onspeleothem mat structures of two limestone caves and on mats and microbialites of fivecoastal lakes ranging in conductivity from brackish to hypersaline. Environmental parameters were correlated to microbial richness, diversity and distribution to explaincolonisation and succession patterns and to identify the seminal bacterial taxa that drive ecosystem development. Diverse microbial assemblages shaped by pioneer colonisation ofabundant coccoid or filamentous Cyanobacteria are described. Geographical separationresulted in significantly different microbial communities between locations and environmental parameters shaped successional stages within the mats. High richness anddiversity of biosynthetic pathway domains is discussed in relation to their potential functions in the environment and the dogma that extreme environments prevent chemicaldiversity is challenged. This study shows a diversity of prolific natural product producing microbial taxa present inextreme environments and constitutes an initial screening effort to target microbial habitats for future exploitation of medicinally active compounds.

Mots clés : Extreme environments, ; Hypersaline, ; Cyanobacteria ; Natural products ; Caves

Présentation

Page publiée le 14 juillet 2017