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Title: Characterisation of novel methylotrophs and the role of xoxF in coastal marine environments
Author: Howat, Alexandra M.
ISNI:       0000 0004 6059 9457
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2017
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Methanol is one of the most abundant volatile organic gases in the atmosphere, and whilst much is known about the sources of methanol, much less is known about the sinks. Methylotrophs are able to use one carbon compounds, such as methanol, as their sole source of carbon and energy. Seawater enrichments with methanol gave rise to the isolation of a novel species of the methylotroph Methylophaga. Some methylotrophs require a rare earth element (REE) when using the alternative methanol dehydrogenase (MDH) XoxF for growth on methanol. Addition of REEs to methanol seawater enrichments, using coastal waters from the south coast of the United Kingdom, showed REE stimulated methanol oxidation, whilst amplicon sequencing of the xoxF5 gene revealed relative increases in unknown sequences. Isolation from enrichments containing lanthanum allowed the cultivation of a new member of the Roseobacter clade, strain La 6. A mutant in the only MDH gene in the genome and complementation and enzyme assays of this strain revealed the essential nature of xoxF during growth on methanol and ethanol. Genome sequencing revealed that stain La 6 has the largest genome of all Roseobacters, at 6.79 Mbp. This facultative methylotroph is metabolically very versatile, growing on some alkanes and aromatic compounds but it was also able to degrade and synthesise DMSP. Multilocus sequence analysis suggests that whilst it shares the core genes with subgroup 1 of the Roseobacters, it shares very little of its pangenome, suggesting unique genetic adaptations. Given this data, the new strain is proposed to be a new genus in the Roseobacter clade. Attempts to express different xoxF sequences in the xoxF mutant of La 6 revealed no phenotype, suggesting there may be as yet unidentified regulatory or accessory mechanisms involved during growth on methanol in this bacterium.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available