Me, you and we... thats what the bacteria talk!

When they had to talk, they say 'me', then recognize 'you' and then also learn 'we'; yes, these are the words the bacteria speak among themselves.

It was my turn to present an article in the journal club here in our department this week. This time, I choose to talk about 'quorum sensing'; the name in "our" language to address their (bacterial) language. Isn't an intresting topic to talk about? after-all, all we are fond of gossips and in this case the ‘bacterial gossips’!

It was an 2009 article in ‘PloS biology’ journal from Bonnie L. Bassler's group who at the first place reported the quorum sensing in the bacteria, vibrio fischeri. It was an amazing experience to learn and share about this incredible system of these tiny little single celled bugs. This particular article is about vibrio harveyi and would like to write here a few things I learnt over reading the article (over a late working night infact :(! ).

Quorum sensing, in short is the phnomenon by which the bacteria synthesis and sence some chemical molecules, with which they can learn about their environment, mainly the number of bacteria around them. This is very important because, a variety of communal behaviours they exhibit are based on this mechanism. For example, in the case of v. fischeri, with the help of quorumsensing they learn about their population density and when they reach a perticular number, they all together express bioluminesence. This will not happen when they stay in a less population density. Like wise, a lot of their functions are tightly associated with the quorum sensing, like virulance, biofilm formation, secreation of antibiotics etc.

In simple tearms, the bacteria talk to each other with chemical words and when they know there are enough candidates to perform a function, they do it together. Its smart, right; to know their own strength before launching an actiton! Being at the top of the evolutionary pyramid, we humans even fail to do so in some instances. I think, they are less complex and do great deals :)!

AHL

Even more, like different people and race have different languages, differnt bacteria use different chemical words for that matter. Broadly classifying, the gram negative bacteria use small molecules like acyl homocerine lactones (AHLs) and the gram positive bacteria use peptides. Initially it was believed that these words are species specific. But later research revealed that there are infact more viz., intra species, inter species and also the ones which are commenly spoken by most of all bacteria. I would love to decode theri language as the following; the intra species i.e., to recognize the cells of its own kind they say, 'me' and for the ones whic are of different species but the same genus, like their ‘cousins’, they say 'you' and for the others, 'we'; in v.fischeri the molecules are called AI-1, CAI-1 and AI-2 respectively. They are chemically different from one another and the ‘AI-2’ is spoken by most known bacteria.

It is believed that with these different words, bacteria try to understand who is out there with them; their siblings, neighbours or strangers some times enemies. Accordingly, they triger specific functions to be performed. In the case of human pathoges, they start invading the host  cells only when they know they are enough in numbers, same way if they recognize an enemy or competition for food, they could synthesise atibiotics and so on. Facinating, isn't it??!! But, that not all about it. We only know very little and they have lot more secrets to be revealed.

Still with the least known, we have developed counter-technology to trick them not to do something unfavourable for us. Its been shown by scientists that by sending some similar but wrong chemical words, the bacteria never know their troops are ready to attack and they stay calm, in the case of pathogenesis. In the field of medicine, the topic now is about the growing ristk of antibacterial resistance among the bacterial pathogens, yet another facinating thing these guys are doing. But this invention has opened a new way of fighting bacterial infections, the next generation antibiotics, so to say. So, thanks to those scientists and PhD students (:O)) who made those discoveries. Let us wish, the current global economic melt down dont stop them from doing much more!