"Feeling of the elbow" in bacteria

This week the names of the 2015 Shao Prize laureates were named. Enforced by the Hong Kong entrepreneur and philanthropist Shao IFU (1907 - 2014), the award has been awarded since 2004 for achievements in the field of astronomy, life sciences and mathematics. Seven laureates of the Shao Prize subsequently received the Nobel Prize. The Lauretes determining the Laureates (The Shaw Prize Foundation) forms three committees for choosing candidates in each of the areas. Then the final decision on the award of each bonus is made by the Council of the Fund. The names of the awarded become known in early summer, and the solemn ceremony takes place at the end of September in Hong Kong.

This year, the prize in the field of life sciences was received by American molecular biologists Bonnie Bassler and Everett Peter Greenberg “for opening” the feelings of the quorum, the ability of bacteria to communicate and coordinate behavior with each other, which offers new ways to combat bacterial pathogenes and module of the microbioma for medical purposes. ”

For a long time, scientists did not assume that creatures such as bacteria were able to somehow communicate with each other and coordinate general actions. The feeling of quorum ( Quorum Sensing ) allows them to achieve this. The mechanism of this phenomenon lies in the fact that with the help of bacteria, which are distinguished into the external environment, can determine how many of their relatives are nearby. When there are a lot of bacteria, the concentration of the signal substance increases, and as a result, all bacteria at the same time change their behavior in a certain way. At the molecular level, this is ensured by the fact that when the threshold concentration of a signal substance in bacteria is reached, the activity of a certain gene increases significantly. This seemingly simple principle allows bacteria to respond to changes in external conditions not as individual creatures, but like cells of a single organism. The feeling of quorum allows bacteria to survive the lack of nutrients, to resist competing bacteria and dangerous toxins. Pathogenic bacteria coordinate their efforts in infecting the host body in order to withstand its immune system.

Sometimes, in a broader sense, the term “quorum feeling” is used to describe the behavior of other organisms: insects or even vertebrates. Or they even try to create robots with this ability. The scheme remains the same: when a certain density of the team is reached, the behavior of its members is coordinated.

It is widely known, for example, that a sedentary or migratory shape of this insect may develop from the larvae of locusts, depending on whether there are many or few such larvae in this place. Also, the feeling of quorum, provided by visual communication, plays a role in the life of the colonies of public insects. Each beekeeper knows that when the population of the hive becomes too large, we should expect grown. A new uterus will appear in the hive, and part of the bees will leave it with the old uterus to settle in a new place. The swarm of the bees flying out of the hive sits somewhere on a tree or on the ledge of the building, and the reconnaissance bees begin to look for a good place for a new house. On the apiary, as a rule, at this moment the beekeeper runs up, sweeps away the entire swarm in a special bag and carries it into a pre -prepared empty hive. If the bees must make a decision themselves, this happens like this. The bees that have found a cavity suitable for the settlement (a cave in the mountains, a niche in a building, a space under the roof boards) return to where the swarm is located, and begin with a bee dance adapted to indicate the direction, agitate other bees to fly there. Some of the bees “succumb to agitation” and visits the selected place. Having returned, they all fulfill the dance again, until finally their number reaches the threshold and the entire swarm will not take off and go to new residence. The experiments showed that in this way the bee swarm is able to choose the best new nest of four to five proposed. Similarly, the place for the new anthill is similar in the case of the destruction of the old ant species Temnothorax albipennis .

In one study in 2006, a quorum of quorum in the Atlantic herring was found , which helps Pisces every evening to gather in large jambs during the propagation period and go to spawning in shallow water. The behavior of fish changes when a certain density is reached - 0.2 herring per square meter. When this happens, herring begins to swim accelerately towards each other, forming a multimillion -dollar flock. After throwing caviar, herring return to the depths and again, until the next evening, swim one by one.

But we will return to the feeling of quorum in bacteria. It was in these creatures that it was first discovered and in them it was most studied. Communication in bacteria, recall, chemical, changes in behavior are achieved during the reaction to the concentration of a certain substance. One of the first studies of Quorum's feeling was made on Aliivibrio Fischeri bacteria. These are sea bacteria capable of luminescence, which can live freely in water, or can live in the body of squid ( Euprymna Scolopes ). Bacteria living separately do not shine if they live in certain organs of squid - photographs, they begin to glow. The “flashlight” of Kalmara is in its mantle cavity, there are especially favorable conditions for the life of bacteria. Since bacteria there accumulates a lot in a small volume, the concentration of the substance they secreted (Acil-Home-Skonton, AHL) increases. Bacteria receptors respond to the increased AHL concentration, the gene is activated, which encodes the enzyme Lucifers, and bacteria begin to glow.

For some time it was believed that the feeling of a quorum based on AHL is characteristic only of marine luminescing bacteria. However, in the 1990s it turned out that it was widespread. For example, they opened that the same substance makes the Pectobacterium Carotovorum to synthesize an antibiotic that helps the Pectobacterium Carotovorum that helps it suppress competing bacteria. Also, when sufficient density, these bacteria begin to isolate enzymes (pectinase and cellulose), which are needed to destroy the cell walls of plants. The bacterium, known as Pseudomonas Aeruginosa , is also used by AHL. When there are quite a lot of praying sticks, they begin to secrete elastasis, which makes a person permeable, violating the compounds between the cells, and also destroys the substances responsible for the immune response. As a result, the patient is developing a difficult to heal infection. In these cases, bacteria of the sticks resemble villains who agree to attack the victim only when there are quite a lot of them.

Of course, bacteria has other substances that provide a sense of quorum. For example, auto-inducer-2 ( Autoinducer-2 , AI-2). It is used by about 30 types of bacteria, including, for example, E. coli. In some bacteria, the role of signaling substances is played by biogenic amins, substances that in multicellular animals act as hormones and neurotransmitters. It is possible that in case of multicellular organisms, the interaction between individual cells began to provide the same mechanisms that were responsible for the feeling of quorum in their unicellular ancestors.

Understanding the mechanisms responsible for the feeling of quorum in pathogenic bacteria allows people to invent new methods of combating diseases, for example, having found a way to destroy the signaling substance and prevent the activation of bacteria. However, in nature, these methods were invented much earlier. It was found, for example, that the Australian algae Delisea Pulchra fights with the colonies of the Bacteria LiqueFaciens stirring on its surface, highlighting the substance that prevents the feeling of quorum.