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.
Do all bacteria use the same signal molecules?
Different bacterial species use different molecules to communicate. There are several different classes of signalling molecule. Within each class there are also minor variations such as length of side chains etc. In some cases a single bacterial species can have more than one QS system and therefore use more than one signal molecule. The bacterium may respond to each molecule in a different way. In this sense the signal molecules can be thought of as words within a language, each having a different meaning.
Can bacteria from one species communicate with those from another species?
There is evidence that interspecies communication via QS can occur. This is referred to as quorum sensing cross talk. Cross talk has implications in many areas of microbiology as in nature bacteria almost always exist in mixed species populations such as biofilms.
What are the benefits of quorum sensing research?
QS research has many potential applications, most of these involve controlling bacteria by interfering with their signalling systems. For example many bacteria rely on QS to control the expression of the genes which cause disease. If we can block the QS systems we may be able to prevent these bacteria from being dangerous.
source : University of Nottingham Quorum Sensing Research Group
