The Elasmobranch-Microbe Relationship: Trimethylamine n-oxide Synthesis, Urea Hydrolysis, and Microbe-Osmolyte Interactions in the Atlantic Stingray, <i>Dasyatis sabina</i>

<p>The elasmobranch osmoregulatory strategy is predicated on the accumulation of nitrogenous compounds, primarily urea and trimethylamine n¬-oxide (TMAO). Despite the abundance of these plasma osmolytes, it is notable that elasmobranchs appear to lack urease and TMA oxidase (Tmase), enzymes that scavenge urea-nitrogen and synthesize TMAO, respectively. However, urease and Tmase are found in many species of bacteria. Therefore, I hypothesized that intestinal bacteria are responsible for urease and Tmase activity in elasmobranchs. Absent dietary nitrogen sources, I evaluated the effects of reduced intestinal microbiota on osmoregulation in Atlantic stingray (<em>Dasyatis sabina</em>) <em>in vivo</em>. <em>D. sabina</em> were given daily broad-spectrum antibiotics <em>per os</em> and monitored for weight loss, plasma osmolality, amine metabolites, urea, and TMAO. qRT-PCR was used to determine the efficacy of antibiotics at reducing the intestinal microbial community and to quantify the hepatic expression of carbomoyl phosphate synthetase III (CPS III), the rate-limiting enzyme in urea production. Though antibiotics significantly reduced the bacterial community in the <em>D. sabina </em>gut, there was no significant change in plasma osmolality, urea, or TMAO. However, amine metabolites changed significantly within control and antibiotic groups including benzoic acid, arginine, creatinine and L-citrulline. Also observed was significant down-regulation of CPS III expression, suggesting that urea production decreased in antibiotic-treated individuals. My findings suggest that elasmobranch osmoregulation is robust to microbiome perturbation and supports the hypothesis that plasma osmolytes are highly conserved in elasmobranchs. This is the first study to test the efficacy and subsequent effect of antibiotics on the elasmobranch intestinal microbiome and osmoregulation.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Discipline thesis:degree_discipline

Ocean Science and Technology

Year dc:date.available

2016

Author dc:creator

• Doucette, Kaitlin Kelly

Contributors dc:contributor

• Darrell J. Grimes
• Andrew N. Evans
• Natalie D. Mylniczenko

• elasmobranch
• microbiome
• urea
• trimethylamine n-oxide
• CPS III
• Biology
• Molecular Biology
• Other Microbiology
• Systems and Integrative Physiology

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/259

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-1285