All ETDs from UAB

Advisory Committee Chair

Robert Thacker

Advisory Committee Members

Asim Bej

James McClintock

Julie Olson

Marc Slettery

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences


The study of sponge-bacteria symbioses is emerging as a prominent field in marine biology and biotechnology, with implications ranging from a fundamental understanding of sponge ecology and insight into the evolution of prokaryote-eukaryote symbiotic interactions to natural products prospecting and bioactive metabolite synthesis. The research conducted herein integrates molecular genetic techniques with ecological methodologies to address fundamental issues of sponge-microbe associations. Bacterial communities associated with the marine sponges Hymeniacidon heliophila and Xestospongia sp. were compared to microbial assemblages from ambient seawater and the sympatric tunicate, Didemnum sp, using replicated clone libraries of 16S ribosomal RNA (rRNA) genes and terminal restriction fragment length polymorphism (T-RFLP) analysis. In clone library analysis, sponge-associated microbial communities exhibited lower species richness and lower species diversity than seawater and tunicate assemblages, with differences in species composition among all four groups. Phylogenetic analyses indicated that these sponge-associated microbial communities are comprised of species-specific bacterial lineages. T-RFLP profiles revealed similar bacterial diversity estimates across the four sources, but varied significantly between the two enzymes used. Both analyses revealed distinct bacterial communities inhabiting each of the four sources investigated, lending further support to the hypothesis that sponges harbor specialist, host-specific symbiotic bacterial communities. iv Chlorophyll a quantification and line-intercept transect surveys revealed sponges hosting photosymbionts accounted for over one-third of the species diversity and abundance of sponges on Caribbean coral reefs of Panamá. PCR-screening showed that most of these sponges (95%) harbor cyanobacterial symbionts, specifically, the cyanobacterium Candidatus Synechococcus spongiarum (79%). Shading experiments conducted on the common reef sponges, Aplysina fulva and Neopetrosia subtriangularis, revealed variable host-symbiont metabolic transfer, with some sponge hosts receiving a substantial portion of their energy budget from their symbionts. Molecular phylogenetics of 16S rRNA genes and the internal transcribed spacer (ITS) rRNA region from the sponge symbiont, Candidatus Synechococcus spongiarum, revealed cryptic diversity among populations and 12 genetically-distinct symbiont clades that ranged in hostspecificity. Multiple clades often inhabited a single host (6 of 18 species). The prevalence of sponge-photosymbiont associations and dominance of symbiont communities by S. spongiarum suggest a major role of this cyanobacterium in sponge ecology, with distinct sub-specific clades offering variable benefits to host sponges.



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