Biology Faculty Articles

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Frontiers in Marine Science


symbiosis, bioluminescence, microscopy, high throughput sequencing, 16S rRNA, tunicate



First Page



The pelagic tunicate pyrosome, Pyrosoma atlanticum, is known for its brilliant bioluminescence, but the mechanism causing this bioluminescence has not been fully characterized. This study identifies the bacterial bioluminescent symbionts of P. atlanticum collected in the northern Gulf of Mexico using several methods such as light and electron microscopy, as well as molecular genetics. The bacteria are localized within the pyrosome light organs. Greater than 50% of the bacterial taxa present in the tunicate samples were the bioluminescent symbiotic bacteria Vibrionaceae as determined by utilizing current molecular genetics methodologies. A total of 396K MiSeq16S rRNA reads provided total pyrosome microbiome profiles to determine bacterial symbiont taxonomy. After comparing with the Silva rRNA database, a Photobacterium sp. r33-like bacterium (which we refer to as “Photobacterium Pa-1”) matched at 99% sequence identity as the most abundant bacteria within Pyrosoma atlanticum samples. Specifically designed 16S rRNA V4 probes for fluorescence in situ hybridization (FISH) verified the Photobacterium Pa-1 location as internally concentrated along the periphery of each dual pyrosome luminous organ. While searching for bacterial lux genes in two tunicate samples, we also serendipitously generated a draft tunicate mitochondrial genome that can be used for Pyrosoma atlanticum identification. Scanning (SEM) and transmission (TEM) electron microscopy confirmed the presence of intracellular rod-like bacteria in the light organs. This intracellular localization of bacteria may represent bacteriocyte formation reminiscent of other invertebrates.


This research was partially made possible by a grant from the BP/The Gulf of Mexico Research Initiative to support the consortium research entitled “Deep Pelagic Nekton Dynamics of the Gulf of Mexico” administered by Nova Southeastern University (NSU). Other components were funded by the JL’s and internal NSU research funds.

Additional Comments

We thank all the PIs and scientists of the DEEPEND consortium, especially the LUMCON crew of the R/V Point Sur for their invaluable help and support throughout this project. Microbial community sequence data are publicly available through the Gulf of Mexico Research Initiative Information and Data Cooperative—GRIIDC (R4.x257.228:0009). We would also like to thank Dr. Lauren Krausfeldt for her invaluable knowledge and advice and Colleen McMaken for lending her support, time, R code, and eyes throughout this project. In addition, many thanks to Dr. D. Abigail Renegar and Dawn Bickham for their patience and guidance through the histological part of this project. One last thanks to Dr. Rosanna Milligan for lending us her mapping expertise in RStudio.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


0000-0002-1637-4125, 0000-0002-5280-7071


F-8809-2011, W-8662-2019



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