Bacterial babble: The science of how microbes communicate

Words by Joe Crutwell, Edited by Lucy Eland

July’s SciBar was on the science of how bacteria talk, and PhD student Ajay  Tiwari’s thought-provoking presentation certainly got the audience gossiping.

Unlike Ajay’s audience, bacteria do not have vocal chords or mouths, so are unable to enjoy chatting about science over a pint, as attendants on the 25th of June did. Instead, they must find other ways of communicating with each other.

This form of communication is known as “Quorum sensing”, and occurs when bacteria secrete signalling molecules into the environment around them, which can then be absorbed by other bacteria close-by.

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When a large number of bacteria releasing these signals are close together, there will be a larger concentration of these released molecules. This increased concentration is a signal to the  bacteria that they can ‘work together’ and coordinate responses to their environment. This can happen both within the same species and between bacteria of different species.

A great example of this is the bacteria Allivibrio fischeri, an organism that lives inside squid species such as the hawaiian bobtail. The bacteria communicate and collectively produce enough light to help the squid ward off predators.

Until recently it was thought quorum sensing was the only method by which bacteria could communicate, but recent research has revealed another way: Bacterial Nanotubes. These large biological bridges can form between two neighbouring bacteria and create ‘information highways’, which allows cells to exchange much more information than quorum sensing alone. As Ajay put it, “If quorum sensing is the bacterial wi-fi, then nanotubes are the wired connection”.

So is this bacterial communication just harmless gossip, or sly scheming? What are these bacteria saying behind our back (and in our bodies)? Well, this information has potentially worrying medical consequences, as it allows bacteria to exchange small amounts of their DNA, known as a ‘plasmid’. The movement of plasmid DNA has been shown in labs to allow the passage of genes that make bacteria resistant to certain antibiotics.

It’s not all doom and gloom however, now that scientists are aware of these methods of communication, they are researching ways to make these bacteria gossip a little less. Rather than yelling “shut up!” into a petri dish, scientists have been blocking nanotube formation and quorum sensing, greatly reducing the bacteria’s ability to form colonies. It is this congregation of lots of cells in the same place that causes the most severe aspects of many diseases, due to the concentrated release of toxins.

Whilst for the health of our bodies we don’t want bacteria to congregate and chat, we actively encourage you to come and mingle at the next SciBar, taking place on the 22nd of August. There, Lynsey Hall will be taking us on a fascinating musical genetic journey.

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