The Interplay Between DMSP and Glycine Betaine Regulation in Labrenzia aggregata

Ellis, Ocean (2023) The Interplay Between DMSP and Glycine Betaine Regulation in Labrenzia aggregata. Doctoral thesis, University of East Anglia.

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Dimethylsulfoniopropionate (DMSP) is a key marine nutrient and forms part of the global biogeochemical sulfur cycle. Glycine betaine (GB) is a nitrogen-containing structural homolog of DMSP produced by a wide range of organisms. Both DMSP and GB are compatible solutes produced in response to osmotic stress. Despite the reported importance and abundance of these compounds, their proposed role in bacterial osmoprotection has so far not been confirmed via mutagenesis of synthesis genes. In this work, the model DMSP-producing bacterium Labrenzia aggregata was investigated as it produces both DMSP and GB. Mutagenesis, transcriptomics and metabolomics were used to understand the interplay between DMSP and GB production and their roles as osmoprotectants in L. aggregata.

L. aggregata growth conditions were screened for those that affected the production of DMSP and GB. Subsequent transcriptomic analysis determined that the key DMSP and GB synthesis genes (dsyB and gsdmt, respectively) were highly regulated by salinity. In order to assess the osmoprotective roles of these two compatible solutes, each synthesis gene was knocked out in L. aggregata. The Δgsdmt strain had abolished GB production and a reduced growth rate when under osmotic stress. The ΔdsyB strain was unable to produce DMSP, however did not exhibit a reduced growth phenotype under high salinity conditions, in concurrence with the existing literature. However, DMSP was indicated to potentially have an osmoprotective role, as the reduced growth phenotype of an L. aggregate ΔdsyBΔgsdmt double mutant in high salinity conditions was partially rescued through genetic complementation with dsyB.

Finally, transcriptomic analysis indicated a putative compatible solute regulator gene and several putative DMSP biosynthesis genes in L. aggregata which were partially characterised using mutagenesis. This study provides tentative support for the role of DMSP as an osmoprotectant and enhances understanding of the relationship between DMSP and GB in L. aggregata.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jennifer Whitaker
Date Deposited: 20 Feb 2024 12:09
Last Modified: 20 Feb 2024 12:09

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