The Hawaiian bobtail squid (Euprymna scolopes)

Talk talk

Bacteria communicate with each other using quorum sensing

Humans talk to one another. Other animals, like birds and whales, also use sound to communicate. But in the bacterial world, conversation is chemical. This chemical communication, or ‘quorum sensing’, is what allows bacteria to synchronise the type of coordinated attack that will leave you feeling sick.

Since the discovery of quorum sensing several decades ago, scientists have realised that all bacteria use it to communicate all the time – within their own population and with other populations of bacteria within the same community.

Quorum sensing is based on population density. Bacteria release communication molecules that float away when the population is small.

Vibrio fischeri

This fluorescence micrograph shows Vibrio fischeri cells, genetically labelled with green fluorescence protein (GFP). While the cells are bioluminescent, the green light seen here is the artificial fluorescence of GFP.


Image taken by E Nelson and L Sycuro, and provided by E Ruby

But when the population is large and the bacteria are all squashed together, the communication chemicals build up to a level that signals to the bacteria that they are surrounded. One universal molecule is used by all types of bacteria to provide information about a community as a whole, whereas more specialised molecules are used by individuals of the same species – each has its own chemical language.

A curious light-producing bacterium called Vibrio fischeri uses quorum sensing molecules to sense when its population has grown to a certain size, at which point all the bacteria in the population switch on their lights. The bacteria are symbiotic, living in an organ of the Hawaiian bobtail squid (pictured above). The bacteria’s luminescence prevents these squid from casting shadows on moonlit nights, which in turn helps them avoid predators.

Lead image:

MJ McFall-Ngai

Further reading

About this resource

This resource was first published in ‘Populations’ in June 2014.

Microbiology, Ecology and environment
Education levels:
16–19, Continuing professional development