How Bacteria Communicate

 

 

First observed by Anton van Leeuwenhoek in 1676, bacteria are the Earth's oldest and most abundant beings. They seem to be little more than rigid vessels filled with DNA and an amorphous cytoplasm.

Bacteria are, however, highly sophisticated creatures. They not only communicate between themselves, they also communicate directly with higher plants and animals.

Communications between individual bacteria are, with slight modifications,  familiar to us. For example, bacteria engage in sexual relations.

Their technique is uncomplicated, one bacterium simply pumps DNA right into the another bacteria through an exceedingly thin walled tube. This enables bacteria to share genetic memories and innovations very quickly.

Bacteria also reproduce by fission, simply splitting into two individuals. It seems, however, that unless they also exchange genetic material with others that the resulting colonies slowly grow old and die.

Bacteria also communicate in a less direct fashion, sending messages to each other that can alter the behavior of thousands of other bacteria at the same time.

To do this, they use small organic molecules called homoserine lactones, or "Autoinducers." Many, if not all bacteria, employ these and related molecules to communicate a variety of environmental parameters, including population density and levels of stress and contentment of the whole community of bacteria.

The communications determine the movements, chemical activities, and reproduction of individual bacteria. This, in turn, leads to changes in the behavior of the whole population.  This process has helped to explain complex behavior between bacteria and higher animals, such as thelight emitting bacteria of squid.

Myxobacteria offer a perfect example of how communications create the appearance of larger - often very complicated - organisms.

Myxobacteria are rod-shaped bacteria found in cultivated soils.

• When water or nutrients are in short supply, Myxobacteria begin to excrete a signal molecule called Factor A.
• When the density of Factor A passes a certain threshold, it means the bacteria are in danger of starving or desiccation.
• When this threshold is passed, the individual bacteria begin to move together into clumps of more than 100,000 individuals.
• Within a short time, their massed bodies form a spherical mound, called a fruiting body, that can be a tenth of a millimeter high.
• The bacteria coat themselves with another message - Factor C - to indicate that they are in the correct position and density.
• When enough bacteria are in contact with other bacteria, Factor C triggers the spore forming genes.
• Some of the bacteria become spores: thick shelled spheres that can resist heat, desiccation, and starvation.
• The mass of bacteria arrange themselves into very complex shapes, pushing out through rotting wood or vegetation and lifting into the air to facilitate the dispersion of the spores by wind, water or a passing animal.

There are hundreds of different species and each of them constructs the most amazing bodies, complete with little stems, tentacles, and flower-like growths all made of the reorganized bacteria.

When I showed Freddy a picture of the fruiting body of a myxobacterium in the February 1997 issue of Scientific American, I said, "It looks just like a coral polyp. Look at what they built.These bacteria must be a whole lot smarter than we thought."

She replied, "That's nothing, they also create us." And, of course, she was right.

Here is a video of Myxobacteria in action.