The chemical ecology of Lingulodinium polyedra and its microbiome

  • Claire Garfield

Student thesis: Master's ThesisMaster of Research (awarded by UHI)


Lingulodinium polyedra is a bloom and cyst-forming dinoflagellate. In harsh environmental conditions, L. polyedra will form cysts that optimize its defense and survivorship. Prior evidence shows that sterilized cysts of dinoflagellates, including L. polyedra, do not germinate well and have low post-excystment survivorship, but cells can recover when bacteria are added. It is hypothesized that recently germinated cysts need a cofactor produced by its microbiome to restart quiescent metabolic pathways. This hypothesis was examined by: (I) confirming the effects of the microbiome on L. polyedra cysts and identifying any unique genomic features of a set of neutral and growth-promoting bacteria; (II) analyzing the metabolome of Oceanicaulis spp. when cultured in isolation and with a perceived host; and (III) identifying the cofactor that supports post-excystment survivorship and determining if growth-promoting bacteria produce it. These data confirm that sterilized cysts show decreased germling survivorship. It was also recorded that growth-promoting and neutral bacteria have some unique genomic features. The chemical data show that the neutral and growth-promoting species of Oceanicaulis spp. have highly similar metabolomes in neutral media, but differ in cyst-conditioned media, showing that they respond differently to the perceived presence of a cyst symbiont. The biological data presented suggests that pyridoxine was most likely the cofactor that cysts require. The chemical data show that Oceanicaulis spp. does produce pyridoxine, although not in a manner that is consistent with the pyridoxine hypothesis. This work tentatively identifies pyridoxine as the critical cofactor for L. polyedra cysts for which they require an exogenous source and identifies genomic and metabolomic differences in bacteria that could be critical to L. polyedra-bacteria symbioses and that are connected to pyridoxine synthesis. Overall, this research has important implications for HAB management, biochemistry of vitamins in the ocean, and algae-bacteria symbioses.
Date of Award26 Apr 2022
Original languageEnglish
Awarding Institution
  • University of the Highlands and Islands
SupervisorDavid Green (Supervisor) & Michael Ross (Supervisor)

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