Microscopic and Genetic Characterization of Bacterial Symbionts With Bioluminescent Potential in Pyrosoma atlanticum

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 bacterial bioluminescent symbionts of P. collected in northern Gulf Mexico using several methods such as light and electron microscopy, well molecular genetics. bacteria are localized within pyrosome organs. Greater than 50% taxa present samples were symbiotic Vibrionaceae determined by utilizing current genetics methodologies. A total 396K MiSeq16S rRNA reads provided microbiome profiles to determine symbiont taxonomy. After comparing with Silva database, a Photobacterium sp. r33-like bacterium (which we refer “ Pa-1”) matched at 99% sequence identity most abundant samples. Specifically designed 16S V4 probes fluorescence situ hybridization (FISH) verified Pa-1 location internally concentrated along periphery each dual luminous organ. While searching lux genes two samples, also serendipitously generated draft mitochondrial genome that can be used identification. Scanning (SEM) transmission (TEM) microscopy confirmed presence intracellular rod-like localization may represent bacteriocyte formation reminiscent other invertebrates.