Johnson, Colton J.

Dinsdale, Elizabeth A.

Sukumaran, Jeet
Vaidya, Naveen K.

2020-06-29

Summer 2020

Thesis

51 pages

The skin of sharks is constructed of dermal denticles that have unique microstructures that influence the attachment and biofilm development of microbes facilitating the presence of a unique epidermal microbiome. Here we use metagenomics to provide the first full taxonomic and functional characterization and temporal stability measurement of the epidermal microbiome of the leopard shark (Triakis semifasciata) across a four-year period.The taxa within the microbiome showed high similarity between all individuals (82.74, Bray-Curtis 100 – dissimilarity index), but varied in relative abundance across years suggesting flexibility in the microbiome. Of the total 597 genera identified, 188 genera were present every year. Pseudomonas, Erythrobacter, Alcanivorax, Marinobacter, and Sphingopyxis were abundant genera overall and shared the leopard skin with Limnobacter and Xyella in year 1 and Sphingobium and Sphingomona in year 2, and Altermonas, Leeuwenhoekiella, Gramella and Maribacter in year 3. The microbiome displayed very high functional similarity between individuals (97.65, Bray-Curtis 100 – dissimilarity index) and maintained functional stability over a 4-year period. The taxonomic flexibility and functional stability of the microbiome was achieved by various microbes providing functional redundancy through weak competition and niche partitioning. The functional stable processes included heavy metal tolerance, nitrogen assimilation, but no nitrogen fixing, conversion of proteins and lipids which indicate the microbiome maintaining a connection with the shark host. Shark metabolism maintains high levels of urea, osmolyte stabilizers such as TMAO, and process protein using ketogenesis, which leads to high levels of lipids, triglycerides, squalene, and ketone bodies. Therefore, the data suggests a passive subsidization of the compounds from the shark to construct a functionally consistent heterotrophic skin microbiome, even with the high turnover rate caused by the difficulty of building a biofilm on the dermal denticles.

en_US

Ecology

Biology

Sciences

San Diego State University

Master of Science (M.S.) San Diego State University, 2020

http://hdl.handle.net/20.500.11929/sdsu:60011