Decoding Prokaryotic Chatter: visualising cell-to-cell communication in bacteria

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It is not generally widely known, but bacteria possess complex chemical communication systems that endow them with a kind of social intelligence. In the simplest sense they are able to signal their presence to other related bacteria and through this census-taking, ensure that their communities express only specific functions at particular population densities. These systems also allow bacterial communities to vote on issues affecting the entire population, and allow bacteria to function as multi-cellular organisms.  

Chromobacterium violaceum is a common soil bacterium that produces striking purple colonies. In relation to the concept above, the expression of this colour is dependent on bacterial communication so that when a small number of bacteria are present it will be white but it turns purple when it receives a communication from other bacteria. When it grows in colonies, individual bacteria of these species are continually sending and receiving signals and consequently the colony will be purple. I have a modified version of this bacterium (CV026) that is effectively mute. It can receive chemical communication signals and respond to them, but cannot send them, so that it will only turns purple if it detects a communication signal from another bacterium. In this sense, it is a unique sensor for bacterial communication giving a striking and direct visualization of this phenomenon.  In these, images the vertical streak is the reporter strain CV026 which in the absence of signals from other bacteria should be white. However, the horizontal streak which is the bacterium Erwinia cartovora, has produced signal molecules, and these have diffused through the media to be recognised by CV026 which has turned purple in response. This is just a test and proof of concept. Further explorations will follow soon.  

 

Decoding Microbial Chatter: Cell-Cell Communication in Bacteria

3 thoughts on “Decoding Prokaryotic Chatter: visualising cell-to-cell communication in bacteria

  1. Fascinating post! Can you explain what you mean when you wrote that chemical communication systems enable bacterial communities to vote? My mind is reeling from the thought that bacteria practice democracy!

    • Thanks Nathan. When some bacteria encounter harsh conditions they can form spores, which are dormant and resistant bodies. This is a big commitment for a population because it means that the community will loose its niche in a particular environment. When a single cell encounters harsh conditions it doesn’t immediately form spores in a selfish manner, but instead sends out a chemical signal that informs other bacteria in the population that it has encountered harsh conditions and wants to sporulate. They then interpret this signal and relate it to their own situation and then in turn “vote” for sporulation or not. The community then makes a decision based on the most prevalent vote.

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