What is Quorum sensing and how do bacteria talk to each other?

The discovery that bacteria are able to communicate with each other changed our general perception of many single, simple organisms inhabiting our world. Instead of language, bacteria use signalling molecules which are released into the environment. As well as releasing the signalling molecules, bacteria are also able to measure the number (concentration) of the molecules within a population. Nowadays we use the term 'Quorum Sensing' (QS) to describe the phenomenon whereby the accumulation of signalling molecules enable a single cell to sense the number of bacteria (cell density). In the natural environment, there are many different bacteria living together which use various classes of signalling molecules. As they employ different languages they cannot necessarily talk to all other bacteria. Today, several quorum sensing systems are intensively studied in various organisms such as marine bacteria and several pathogenic bacteria.

Why do bacteria talk to each other?

QS enables bacteria to co-ordinate their behaviour. As environmental conditions often change rapidly, bacteria need to respond quickly in order to survive. These responses include adaptation to availability of nutrients, defence against other microorganisms which may compete for the same nutrients and the avoidance of toxic compounds potentially dangerous for the bacteria. It is very important for pathogenic bacteria during infection of a host (e.g. humans, other animals or plants) to co-ordinate their virulence in order to escape the immune response of the host in order to be able to establish a successful infection.

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For recent reviews on QS see:

Bassler and Losick (2006); Williams et al. (2007); Diggle et al. (2007)