Just to remember ;)I started my internship in the startup Glowee 3 weeks ago. The goal of this startup is the utilization of bioluminescent genes from the Vibrio fischeri strain, expressed by Escherichia coli strain, in order to bring light into streets with signaletics or showcases but also during special events.[1] During this internship, I work on the bioluminescent light, in order to ameliorate the light intensity, the time of luminescence and have the cheapest protocol. Last time I explained to you how bioluminescence works (if you didn’t read my article I invite you to read it before :) ) but also the symbiosis between the cuttlefish Euprymna scolopes and the bacteria Vibrio fischeri. Last time I teased you about the lux operon, but I will develop it in the next post. So for the moment, I will just tell you more about this amazing symbiosis. Symbiosis - the simple way to live togetherThe bioluminescent bacteria V. fischeri apparently take the control of the internal clock of Euprymna scolopes cuttlefish. In fact, the team of Margaret McFall-Ngai of the University of Wisconsin in Madison (USA) discovered that V. fischeri is implicated in the circadian cycle of the cuttlefish and not only in the light production. [2] To remind you, circadian cycles are biological cycles of 24 hours where the organism is regulated. Moreover, this rhythm regulates most of our biological and behavioral functions. Solar light plays an important role in this circadian regulation. ID card of Euprymna scolopes and Vibrio fischeriEuprymna scolopes is a cuttlefish, from the family Sepiolidae. It measures about 30 millimeters for 3 grams. [3] This organism live in the Pacific ocean, near Hawaï. E. scolopes feeds mainly on shrimps, accessible in shallow waters. Picture of Euprymna scolopes https://katiesuedavis.wordpress.com/2011/12/20/about-the-header-vibrio-fischeri-and-euprymna-scolopes/ Vibrio fischeri is a motile - gram negative - seawater bacteria. It specificity is bioluminescence, in fact this bacteria brings light into his host in the sea. The bioluminescence is allowed by the expression of proteins expressed with lux operon. Plate with bioluminescent Vibrio fischeri culture https://www.flickr.com/photos/55386616@N07/7082321451. Who, where, when . . .In our example, the cuttlefish could not shine during the night without V. fischeri. This blue light allows it to lure the predators and hunt some shrimps. [4] This cohabitation is mutually beneficial; bacteria use nutrients present in the cuttlefish and this one provide a favorable environment. But how this symbiosis works? And where does it start? V. fischeri is the only one capable of effectively colonizing the luminous organs of Euprymna scolopes. In fact, the symbiosis starts at the birth of the cuttlefish. The luminous organ of Euprymna scolopes has ciliated arms, and this traps the marine bacteria ... including V. fischeri which advances thanks to their flagellum. When the bacteria is inside the animal, the expression of several light genes is changed. For example, V. fischeri produces toxic molecules for others bacteria or in contrary attracts other Vibrios with chitobiose (major product of chitinase).[5] But Euprymna scolopes also acts on bacteria, by regulating the number of bacteria, not to produce light when it is daylight. When the night is coming, the number of bacteria increases, thanks to quorum sensing (see below). Scheme of the beginning of the symbiosis between the two organisms. Research project on this mechanismA lot of researchers tried to understand how V. fischeri acts on this bioluminescence (from a genomic and proteomic point of view). I told you about quorum sensing. But what it is? This phenomenon is induced when the bacteria releases chemical self-inducers to warn others of their presence, and when the level of autoinducers reaches a certain density the bacteria activates genes that react with proteins, here luciferase, to emit light. With this last phenomenon, researchers deduced that cuttlefish circadian cycles are regulated by the bacteria itself. Tests were carried out in the laboratory, cuttlefishes that had no Vibrio fischeri, could not become luminescent and did not produce the cycle of expression of the escry1 gene (one of the genes involved). Even by imitating bioluminescence with blue light, the cycle was not induced. In the latter case, if the bacteria is present but incapable of producing light, the cycle is activated when the dummy light is used. This proves that bacteria and light are thus essential to control the gene cycle in cuttlefish. [6] Bonus: The wonder organs of Euprymna scolopesAdded to this, Euprymna scolopes had a specific reflective organ. Composed by several parts, as reflectors, lenses or photocytes. Each part acts as a mirror, amplifying the light intensity! We keep this in mind for our project, to increase the light by this kind of systems. Scheme of a light organ in cuttlefishes, from : http://champo-tpe.e-monsite.com/pages/content/ii-type-de-bioluminescence/a-structure-des-organes.html. For the next blog posts . . .I explained from which organisms this bioluminescence comes from, and next time I will explain you the mechanism at a genetic level. For the followings posts I will talk about what I did during the internship and probably other nice stuff ;) References
5 Comments
Isabelle
31/3/2017 05:54:46 am
Hello Hortense ! It's an amazing project, and i'm happy to see you like it ! In one of your post, you say "This phenomenon is induced when the bacteria releases chemical self-inducers to warn others of their presence, and when the level of autoinducers reaches a certain density the bacteria activates genes that react with proteins, here luciferase, to emit light." . So, how you emitted this comportement in your plate and What is the environnement in the plate to allow the Bioluminescence ? Bis :)
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Hortense
20/4/2017 06:08:17 am
Hi Isa,
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Hortense
20/4/2017 06:10:29 am
To answer to you second question:
Fairouz
7/4/2017 01:46:00 pm
Hello Hortense!
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Hortense
20/4/2017 06:13:37 am
Hello Fairouz
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