The Light at the end of the tunnel Ocean (Vibrio Fischeri)

Ever since I was a little girl, I have been fascinated by the immense variety of life that exists within the depths of the ocean. When I first moved to Georgia from Brazil I wanted to visit the Georgia Aquarium. It seemed like everyone I talked to had such a positive reflection of their experience there. As a college student, however, I kept pushing it off due to a lack of time and money. It was not until I discovered that the aquarium was one of the options given in my microbiology course that I decided I should finally visit! I am thrilled that I went. The Georgia Aquarium was a wonderful experience filled with overwhelming visual stimulation from start to finish.

Moreover, during my visit day at the aquarium I did not use a tour guide I just explored on my own, and I am so glad I did because I was able to look at everything without no rush. To me, that is one of the reasons why my experience was so pleasant because I could read every poster and learn about all the sections in each gallery.

During my visit, I learned that there are more than 10 million gallons of fresh and marine water in total in the aquarium. The aquarium divides their exhibits into seven total galleries being: Aquanaut Adventure, Cold Water Quest, Ocean Voyager Built by The Home Depot, SunTrust Pier 225, Southern Company River Scout, Tropical Diver, and AT&T Dolphin Coast. In every corner of the aquarium, there was an interesting organism; which was interfering with my decision-making process in selecting a specific organism to learn more about. However, as soon as I found the bobtail squid and about its mutually beneficial relationship with the bacteria Vibrio fischeri I knew I had my organism.

Domain: Eubacteria
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Vibrionales
Family: Vibrionaceae
Genus: Vibrio
Species: Fischeri

 

When the moons reflect its light in the sea it crosses the water deep into the ocean, if the light is not able to cross the body of an organism it will generate a shadow, and well that is not good if they do not want to be someone’s dinner. So, many marine organisms have their ways to disguise and hide from predators. In this blog, we will learn how the bioluminescent bacteria Vibrio fischeri helps the bobtail squid to not cast a shadow making them a successful predator at night.

Vibrio fischeri is a gram-negative bacterium that is naturally found mostly in seawater and sometimes in fresh water as well; they are a kind of bioluminescent bacterium and they are usually found in a symbiotic relationship with marine animals and bobtail squid is only one of them. More specifically, they offer their ability to have a bioluminescent organ that emits light in which neutralizes the light reflected by the moon in ocean floors and allow the bobtail squid to move around without casting a shadow, camouflaging, therefore, being a successful predator at night. In exchange, the bacterium that forms this light organ gets a nutrient-rich and stable environment for attachment. Their bioluminescence is possible due to the expression of a set of genes known as the lux operon. In order to communicate and synchronize the light at the same time, this bacterium is regulated by LuxR-LuxI quorum-sensing system.

The reason why I became intrigued with this bacterium is that, like any other bacteria, they do behave quite differently depending on its environment, but most intriguing is that when they are living freely they are not bioluminescent that means that they do not produce light at all. However, when they attach to form biofilms they start to secrete autoinducers resulting in the increase of cell density to form this light organ in which will eventually produce light.

In addition, one of the reasons why this bacterium stands out from another organism to me is because it changed the way I perceive bacterium processes. For example, before knowing about this bacterium I would think of quorum sensing as something negative because often times they release toxins that can be pathogenic to us humans. But now, I think that quorum sensing can be just as beautiful as it can be fatal; because not only they are able to cause death, they are also able to emit something so beautiful such as light.

Since in the aquarium I was not able to take a picture of a Bobtail squid I will leave below my favorites youtube videos about this amazing organism:

Living together: The Hawaiian Bobtail Squid – Vibrio fischeri Association

Sources:

  1. https://www.nottingham.ac.uk/quorum/fischeri2.htm
  2. https://microbewiki.kenyon.edu/index.php/Vibrio_fischeri 
  3. https://www.youtube.com/watch?v=0wtLrlIKvJE
  4. https://phys.org/news/2010-11-symbiosis-bobtail-squid-bacteria-buddies.html
  5.  https://www.georgiaaquarium.org/experience/explore/galleries/cold-water-ques