Saturday, September 28, 2013

Prokaryotic Saturday: tales of a glowing bacteria

Today is Saturday and it is also the first Prokaryotic Saturday of this blog!!! Yeyy!

So, today I want to talk about this little crazy guy called Vibrio fischeri.

I won’t say anything new, so if you already know what this guy does, then you can safely stop reading this post………………………… Now that I have that part of the audience that does not know or it is just too bored and doesn't have anything more interesting to read, let me continue. V. fischeri is a gram negative bacteria, which lives in the mantle of the hawaiian bobtail squid. This bacterium is the proud owner of the “canonical quorum sensing system”. It is called 'canonical' because it is by far the most studied and the best described system, since this one was the very first quorum system ever discovered (around 1980, by Nealson et al.).  

You might be wondering what does “quorum sensing” mean. Well, quorum sensing is when bacteria modify in some way the expression of their genes depending on the amount of other bacteria in the medium (cell density). It is believed that bacteria are able to “talk” using chemical signals, not only with other bacteria of the same species but also with organisms of other kingdoms. It’s like when you go out by yourself, you can have a good time of course, but definitely it is not the same when you go out with your friends. And the more you are, the more fun it is. Same here, the more bacteria there in the medium the more behavioral changes they express.

Although the topic of this Prokaryitic Saturday it is not quorum sensing (I probably talk about it later), you can visit Dr. Bonnie Bassler webpage (or just google her name) and learn more about this amazing and tremendously interesting field.

Now, for some reason I feel this post is already getting boring. So, let’s go back with the V. fischeri. This bacterium lives in the mantle of the hawaiian bobtail squid as I just told you. And when you isolate it in the lab you can create some funny stuff like this petri dish:



Because V. fischeri is a bioluminescent bacteria, it glows in the dark, and you don’t have to do anything. :o 

But how does this happen? Here is when the quorum sensing thing comes into action. This bacterium can glow thanks to the expression of two genes, luxR and luxI. These genes are part of the operon luxICDABE. These two genes, luxR and luxI produce two proteins, proteins LuxR and LuxI (yeah, people were not very creative here). And protein LuxI triggers the synthesis of an autoinducer, the homoserine lactone molecule (HSL). So HSL accumulates in the intra and extra cellular environment, and as the number of cell increases, so does HSL. And when concentration of this autoinducer reaches something around 10 ug/ml, HSL binds protein LuxR, then this complex (LuxR-HSL) binds to the operon luxICDABE and bang!!! Genes express and cells glow like crazy!! woooww!!!

Isn’t this cool?

But now, don’t you wonder why? I mean, a glowing bacteria? Why is this crazy bacteria producing light? Maybe she just like showing off.

Well, actually not. There is a good reason and it is the same reason that explains most of animal's behaviors (other than human): survival.
   
The squid, which is the home of V. fischeri, uses this bioluminescence to hide from predators in a very clever manner. This squid (Euprymna scolopes) hunts at night, and uses the light emitted by V.fischeri to simulate the moon light and hide its shadow. The next video of Dr Siouxsie Wiles (@SiouxieW) explains it better. But the thing is, V.fischeri gets food from the squid, and the squid gets an “invisibility cloak”. Plus other few thing, like this light emission mechanism also help the squid to attract predators and mates. So, it's a win-win. 


Now, you can’t say this is not cool.

So that is it. First Prokaryotic Saturday went well, I think. Although you can find many animations and videos online about the LuxI/LuxR gene regulation process, I have a very cool animation (which I created, hehe) so email me if you want to see it, I will send it to you (for some reason I couldn’t upload it here, sorry). And if you have any questions or suggestions, please, leave them in the comments or at @ale_alvarador. 

See you next week!

8 comments:

Emilio Nafarrate Rivera said...

I just loved the Prokaryotic Saturday of this week... At the first sentence I know it was you Ale... I hearded about V. fischery like everybody else, when u read about quorum sensing... But i did know a lot of things that now I know thanks to Prokaryotic Saturday... Thanks Ale

I promise to write about the clever infection system of Lysteria monocytogenes on next PS, I read about it know that I'm giving some courses at LALA factories about GMP (good manufacturing practices) and DTF(diseases transmited by foods).

see u...

PS read my next post... I'm inspired...

Emilio Nafarrate Rivera said...

I just loved the Prokaryotic Saturday of this week... At the first sentence I know it was you Ale... I hearded about V. fischery like everybody else, when u read about quorum sensing... But i did know a lot of things that now I know thanks to Prokaryotic Saturday... Thanks Ale

I promise to write about the clever infection system of Lysteria monocytogenes on next PS, I read about it know that I'm giving some courses at LALA factories about GMP (good manufacturing practices) and DTF(diseases transmited by foods).

see u...

PS read my next post... I'm inspired...

naga said...

a good start ale. would like to see that u and others (good that emilio is showing interest) continue with these kind of posts. felicidades

Alejandra said...

Emiliopoliss!!! Miss u muchototote! A todos! :)
Sure, you can write anytime! I'll wait for that post.

Salu2 y abrazos.

Kryz Montenegro said...

No hay duda que la inteligencia no se limita a especies. Y una forma de demostrarlo es la capacidad de sobrevivir y como hacer uso de lo que se tiene para colaborar.
Muy interesante Ale, gracias por compartirlo.

Jesús Jiménez Ascencio said...

Hola Ale:

Excelente tema el que elegiste, había escuchado antes de esta bacteria y su peculiar propiedad. Lo que realmente me sorprende es como las funciones regulatorias son necesarias para la expresión del fenotipo de bioluminiscencia a través del quorum sensing. Pienso que este tipo de simbiosis entre organismos superiores y bacterias, además de ser algo benéfico para ambas partes, también nos dá una pauta para describir fenómenos de comunicación entre bacterias o hasta otros reinos como mencionas. Se ha estudiado la influencia de análogos del autoinductor en la inducción de bioluminiscencia en V. fischeri, algunos muestran poco o ningún efecto sobre dicha inducción, lo que nos lleva una vez más a la comunicación celular pues son las señales extracelulares las que nos permiten describir la inducción de los genes de bioluminiscencia de V. fischeri de otras bacterias marinas que coexistían en un mismo entorno, por ejemplo se ha demostrado que el autoinductor 3-oxododecanoyl HSL de Pseudomonas aeruginosa es un inhibidor para la autoinducción de los genes de V. fischeri, lo que sugiere que es posible que una especie con una alta densidad celular (hablando de P. aeruginosa), pueda producir una señal que interfiera con la capacidad de otras especies para colonizar exitosamente un hábitat específico. Estos pequeños detalles de comunicación celular son los que tienen gran significancia para poder llevar a cabo sus funciones fisiológicas.

Este artículo habla un poco más sobre el tema: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC178026/pdf/1782897.pdf

¡Saludos!

Alejandra said...

Hola Jesus. Los inducers son bastante específicios, por eso los análogos no tienen efecto. De hecho algo que me sorprendio muchisimo es que la longitud de la cadena de carbonos de los inducers esta relacionada con la especificidad del mensaje. ¿No esta genialisimo eso? Y eso de las intereaccione sentre mensajes que mencionas es todavía más interesante. Resulta que hay varios tipos de mensajes, no nada mas de quorum sensing, pero otros conocidos como quorum quenching, es algo así como hablar o no hablar. Y lo más impresionante es que entre los microorganismosd e una comunidad pueden enviarse diversos tipos de señales confusas, una vez más la clave es interacción... está genial! Osea, qué complejas son las relaciones microscopias no? Voy a checar tu articulo. Y si puedes lee el de "Bacterially speaking" de Bonnie Bassler, habla un poco más de los operons que regulan quorum sensing en pseudomonas y trae una bonita introduccion de quorum quenching. Salu2!

Alejandra said...

AAAAH, pues mira, en este articulo que mandas está eso de los autoinducers y su especificidad...