Metabolomic characterization of coral species susceptible to stony coral tissue loss disease
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Deutsch, Jessica M.
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Abstract
Coral diseases pose a significant threat to marine ecosystem stability, jeopardizing the
biodiversity, production, and resilience of coral reefs worldwide. The emergence of stony coral
tissue loss disease (SCTLD) ravaging Florida and Caribbean reefs has resulted in massive loss of
coral. For the 22+
species affected within the Caribbean basin, variance in inter- and intraspecific
SCTLD susceptibility has been reported, necessitating inquiry into what factors may underlie this
variation. As SCTLD persists, it is vital to understand underlying chemical mechanisms that
mediate symbiosis and pathogenesis between coral holobiont members during healthy and
diseased states. A variety of interactions within the stony coral holobiont occur amongst the coral
animal (host), endosymbiotic eukaryotic algae (family Symbiodiniaceae), prokaryotic microbes,
archaea, fungi, and any organism or other molecules that may pass through the water column.
Metabolomics, the comprehensive study of small molecules within an organism, provides a
readout of the biochemical activity and physiological state of the sampled organism. Advancement
in untargeted metabolomics-based strategies offers an opportunity to connect cellular pathways
with biological mechanisms, which is critical in unravelling the biological roles of metabolites in
cellular physiology. One challenge in coral metabolomics is the sparsity of database spectra,
necessitating time intensive manual metabolite annotation efforts. Untargeted high-resolution
mass spectrometry-based methodology is combined with innovative in silico annotation tools to
facilitate metabolite annotation. Such an approach is used to delineate the metabolome profiles of
visually healthy coral species, visually healthy and SCTLD-affected corals, and identify specific
metabolites underlying this variation. A culture-based approach using coral-derived
Symbiodiniaceae guides the assignation of the biosynthetic source of metabolites. Chemical
classes that were variably detected between healthy coral species included acylcarnitines, betaine
lipids, and vitamin E derivatives. Metabolome profiling of Montastraea cavernosa from a SCTLD
endemic Florida reef site revealed at least 1/3 of the metabolites that differentiate the corals based
on SCTLD status are biosynthesized by Symbiodiniaceae, including glycolipids, betaine lipids,
and vitamin E analogues. Analysis of metabolome extracts from Orbicella faveolata colonies with
varied SCTLD-susceptibility uncovers a notable effect of the sample period and reef location on
the metabolome variation. Tocopherol and acylcarnitine analogues were among metabolites that
contributed to differences between corals based on SCTLD related grouping schemes. Stony corals
interact with prokaryotic microbes which may produce metabolites that contribute to coral
chemical defense mechanisms. Coral-derived bacteria were selected as probiotic treatment
candidates through screening for isolates that were active against putative SCTLD-associated
pathogens. The metabolomics data acquired on these coral-derived bacteria coupled with the use
of in silico data analysis tools facilitates rapid dereplication of metabolites from ecologically
relevant pathogenic and candidate probiotic bacteria. Ultimately this dissertation demonstrates the
viability of untargeted metabolomics to generate and support hypotheses for coral metabolomics
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Date
2024-06-24
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Text
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Dissertation