Bacteria can talk to each other: by using signal substances they inform their neighbours as to whether or not it is worth switching certain genes on or off. This communication between bacterial cells is essential for the adaptation to changing environments and for the survival. What exactly do bacteria learn from the signal substances? There have been two theories: the release of signal substances is understood to be either a cooperative strategy to determine the cell density (quorum sensing) or alternatively a non-cooperative strategy in which the signal substance is only used to determine the dimensions of the space surrounding the cell (diffusion sensing). However, both theories have not been shown to work under natural conditions, which usually are much more complex than those in laboratory.

Scientists from the GSF National Research Center for Environment and Health (member of the Helmholtz-Gemeinschaft) have been able to show that both approaches are merely theoretical extremes of an overall strategy by which bacteria determine whether the amount of energy required to produce substances, such as antibiotics or exoenzymes, is worth while in a particular environmental situation. This overall strategy called efficiency sensing combines existing theories and first allows an understanding of how bacterial communication works and which purpose it serves, explains Dr. Burkhard Hense from the GSF Institute of Biomathematics and Biometry (IBB), who analysed the various strategies using mathematical models.

Microbial communication was first discovered in mixed liquid laboratory cultures, e.g. of the luminescent bacterium Vibrio fischeri, which only shows bioluminescence from a certain cell density. Therefore, the release of signal molecules was first understood as a strategy to determine the cell density (quorum sensing). With its cooperative approach, however, quorum sensing does not provide a stable survival strategy from an evolutionary p
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Contact: Heinz Joerg Haury
oea@gsf.de
49-893-187-2460
GSF - National Research Center for Environment and Health
2-Apr-2007