All ETDs from UAB

Advisory Committee Chair

Asim K Bej

Advisory Committee Members

Stephen A Watts

Casey D Morrow

Thane R Wibbels

Jason G Linville

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences


For over 500 million years, our planet’s self-replicating prokaryotes have colonized multicellular host organisms, forging complex interdependent relationships under the selective pressures of the natural environment. Recently, the use of high-throughput sequencing (HTS) technology targeting metacommunity DNA has uncovered the unprecedented diversity and metabolic processes of these communities. Such information has extensively been investigated in the guts of higher bilaterian organisms, such as mammals including humans. One of the early bilaterian organisms that have been linked to humans are the sea urchins, the gut microbiota of which have not been sufficiently studied. Thus, the objective of this dissertation was to explore the structure and function of the microbiota in the gut systems of two sea urchins, Lytechinus variegatus (green) and Strongylocentrotus purpuratus (purple), which are dominant grazers of marine seagrass and algae in their natural coastal marine habitats. These organisms possess primitive deuterostome gut systems whereupon ingestion, the mucous-producing cells in the pharynx envelop their feed and microbiota forming “gut digesta” that remains separate from the “gut tissue” while transiting through the gut lumen. In this study, we have used metagenomics and bioinformatics tools to reveal the microbial communities in the gut tissue and gut digesta in the green and purple sea urchins. The results showed unique abundances of Epsilonproteobacteria, primarily representing Arcobacter in the gut tissue of the green, whereas Sulfurimonas and Arcobacter were observed in the purple sea urchin. However, the gut digesta was dominated by Gammaproteobacteria representing Vibrio in the green, and Psychromonas in the purple sea urchins. Functional metagenomics analysis further supported the gut digesta as the primary location for the microbial metabolism of macromolecules in both green and purple sea urchins. Moreover, genes in the reduction and fixation of nitrogen into ammonia, and subsequent assimilation into organic molecules primarily for the synthesis of nucleotides and amino acids were abundant in the metagenomes. The results of this study revealed the distinct gut microbial community composition and metabolic processes benefitting two ecologically and evolutionarily significant marine invertebrates, and their potential impact at various trophic levels of their natural habitats.



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