I recently visited the Georgia Aquarium and fell in love with one of the bacterial species I encountered by the name of Vibrio Fischeri. I have discovered so many interesting things regarding the cellular structures and chemical mechanisms within this microorganism that I cannot wait to share with you.

This micrograph shows fluorescently stained Vibrio fischeri cells. Image taken by E Nelson and L Sycuro, provided courtesy of the Vibrio fischeri Genome Project.

 This interesting microbe has a rod shape, is approximately 0.8-1.3 micrometers in diameter and 1.8-2.4 micrometers in length. They can travel through the ocean and other liquid mediums using 1 to 3 polar unsheathed flagella on the surface of their outer membrane. Vibrio Fischeri is also a unicellular microbe. A unique feature of this unicellular bacterium is that they can assemble and colonize an entire functional organ within the Bobtail Squid. This microbe consists of two chromosomes, and their genome has been fully sequenced. Within both chromosomes, there are 4,284,050 base pairs with approximately 1129 base pairs per gene. In total, this bacterium has around 3,800 genes! Additionally, the cell is oxidase-positive and classified as gram-negative with a thick peptidoglycan layer surrounding a cytoplasmic membrane.

Genome maps of Chr I (2.9 Mbp) and Chr II (1.3 Mbp) of V. fischeri ES114. (From the inside) Ring 1, rrn operons (red); tRNAs (green). Ring 2, “foreign” elements (black). Ring 3, type IV pilus loci (red). Circle 1, G+C content over a 200-kb window with 5-kb steps; red and blue denote G+C content higher and lower than average, respectively. Circle 2, homology on + and – strands to V. cholerae N16961 ORFs, determined by using FASTA; red, e value < -30; green, e value > -30. Circle 3, location in kilobases.

 One of the unique and fascinating components of this bacterium is its ability to produce bioluminescence. This component makes the Bobtail Squid one of the most mesmerizing creatures in the depths of the ocean! The Bobtail Squid has appendages on its side that find and filter these bacteria through its body to its light organ. Once these bacteria find the correct organ within the Squid, they shed their flagella to create a better surface area for attachment to the organ. Within the Vibrio Fischeri genome, there is a gene called the lux operon which encodes the enzyme named luciferase. Luciferase catalyzes a reaction that produces the light that the Bobtail Squid emits to avoid predators.

Figure 2: The Hawaiian bobtailed squid, Euprymna scolopes. This organism is the host for Vibrio fischeri cells. The squid and V. fischeri cells share a unique, symbiotic relationship. This image is courtesy of M. J. McFall-Njai and E. G. Ruby. University of Hawii, National Science Foundation (12).

 These microorganisms are a significant focus of study within marine biology, physiology, biochemistry, and even ecology as we find out more about how these bacteria can adapt to a wide variety of ecological niches, and further study the processes behind bioluminescence. I am excited to further learn and discover what Vibrio Fischeri have to offer Bobtail Squids and the world!

Here are some intriguing videos on the Bobtail Squid and its Bacterium. Check them out if you would like to learn more:

Reference/Sources:

1. http://www.pnas.org/content/102/8/3004

2. https://microbewiki.kenyon.edu/index.php/Vibrio_fischeri

3. https://microbewiki.kenyon.edu/index.php/Vibrio_fischeri_NEU2011

4. https://socialinsilico.wordpress.com/tag/vibrio-fischeri/

5. http://www.pnas.org/content/102/8/3004.short