Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Counting Heads or Measuring Space? - A Close Look at Bacterial Communication Strategies

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 point of view, because "cheaters" can also benefit from the released substances without having to pay for their production. The approach of diffusion sensing is slightly simpler: it is assumed that the bacterium uses the signal substances to measure whether the cell sourrounding space is adequate to achieve the concentration of active substances required for efficient action. This is in contrast to the quorum sensing concept, when other bacteria do not necessarily have to be involved.

In a more complex and heterogeneous environment, such as the root compartment of plants, however, both communication strategies have their weaknesses: the root surface is a highly complex matrix in which solids, gels, liquids and gases are found within a small space and where numerous other organisms interfere with the communication on top of that. Therefore, within the framework of the interdisciplinary project “Molecular Interactions in the Rhizosphere” Hense and his colleagues of the GSF-Institute of Biomathematics and Biometry (IBB) investigated this habitat in cooperation with Professor Dr. Anton Hartmann and Dr. Michael Rothballer from the GSF Department Microbe-Plant-Interaction ( AMP).

Based on experimental observations, it could be shown by mathematical modelling that the spatial distribution of the bacteria in the rhizosphere often has a stronger influence on the communication than the cell density or the dimensions of the space surrounding them. Therefore, the scientists developed a synthesis of the two models, which they named “efficiency sensing”: the microbes always perceive a mixture of cell density, cell distribution and diffusion limitation due to spatial conditions, because these aspects cannot be strictly separated – it depends on the circumstances and habitat quality which aspect is predominant. The problem of the “cheaters“ is also avoided, if the spatial distribution of the cells is taken into consideration: on root surfaces or in biofilms related organisms often form clonal micro-colonies. Since in this case all relatives are in the immediate proximity, they are also most likely to encounter the signal substances and the reactions triggered by the signal substances – strangers are largely excluded. Thus, such aggregations of closely related cells allow stable cooperation in terms of evolution and offer effective protection from external interference.

“Efficiency sensing was developed based on observations and models of the conditions on root surfaces, but it can be transferred to other bacterial habitats”, Hense emphasizes. Therefore, manipulations of the bacterial signal system are a highly promising approach in various spheres of life, e.g. in agriculture (support of plant-growth-promoting bacteria, inhibition of noxious organisms) or in medicine (fighting pathogens). A better understanding of the ecological mechanisms of bacterial signaling under natural conditions, as is possible with the “efficiency sensing” concept, is a prerequisite for this.

Michael van den Heuvel | alfa
Further information:

More articles from Agricultural and Forestry Science:

nachricht Forest Management Yields Higher Productivity through Biodiversity
14.10.2016 | Technische Universität München

nachricht Farming with forests
23.09.2016 | University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES)

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>