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Postgraduate Students

Ms Emily Flowers

Linking Microbial Diversity and Function in Estuarine and Marine Sediments: what is the function of biodiversity?

Global bacterial biomass is enormous, accounting for between 60 and 100% of plant biomass. However, as a tiny proportion of all bacteria have been grown in laboratory culture (typically only between 0.0001 - 10% of total bacterial cells), we know very little about these organisms within the environment. The revolution in molecular genetic techniques has demonstrated the huge diversity of bacteria, but this only underlines how little we know about the activity and function of individual bacterial types in the environment. In addition, this raises fundamental questions, such as, what is the purpose/importance of this biodiversity for global biogeochemical cycles and ecosystem function?

A new approach to link function and bacterial identity is "Stable Isotope Probing", where the incorporation of 13C-labelled substrates into bacterial biomarkers is used to identify the individual bacterial types actively metabolising the labelled substrate. When this is combined with analysis of the prevailing environmental conditions it provides unique information about the activity and physiology of bacterial types, even if they cannot be cultured in the laboratory. 13C-substrate incorporation: into DNA provides identity of actively growing bacteria, into RNA gives similar information but the bacteria do not have to be growing, just active and into phospholipid fatty acids and other lipids give possible identity and information about the physiological status of the cell (e.g. starving, high pressure or high temperature adapted).

All approaches are combined to investigate complex bacterial interactions within marine and estuarine sediments which play a major role in biogeochemical cycles and have high bacterial biomass. This will be conducted at a range of sites to provide unique information about sedimentary bacterial biodiversity and function in contrasting environments (e.g. estuaries, mud volcanoes, gas and fluid seeps, gas hydrate deposits).